HomeMy WebLinkAboutagenda.hpc.20240410.worksessionAGENDA
ASPEN HISTORIC PRESERVATION
COMMISSION
April 10, 2024
5:30 PM, City Council Chambers -
3rd Floor
427 Rio Grande Place
Aspen, CO 81611
I.Work Session
I.A Roofing Materials Work Session - NOT A PUBLIC HEARING
Roofing Materials Work Session Memo.20240410.pdf
Exhibit A.COA Historic Preservation Design Guidelines.Chapter 7.pdf
Exhibit B.Preservation Brief 16.pdf
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MEMORANDUM
TO: Aspen Historic Preservation Commission
FROM: Kirsten Armstrong, Principal Planner Historic Preservation and Stuart Hayden,
Planner II Historic Preservation
MEETING DATE: April 10, 2024
RE: Roofing Materials Work Session
Background:
City staff and the Historic Preservation Commission (HPC) have heard from many property owners
regarding the increasing (in)feasibility of installing and/or keeping wood roofing materials on structures in
Aspen. For nearly 96% of properties in Aspen, the market provides a glut of fire code-, building code-, and
land use code-compliant alternatives. On those properties listed on the Inventory of Historic Sites and
Structures, however, roofing materials are limited to those which meet the Historic Preservation Design
Guidelines. Although tradeoffs may occur on a case-by-case basis, “Chapter 7: Roofs” of the Guidelines
all but prescribes wood shingles for most of these properties. Together, Guidelines 7.7 and 7.8 call for
roofing material that is “similar to the original” in style, physical qualities, color, scale, and texture (Exhibit
A). Lest a metal roof suffice, the guidelines explicitly call such material “inappropriate” for the roof of a
primary building on an Aspen Victorian property. For lack of a better alternative, staff and HPC have long
approved “earth tone” architectural asphalt shingles, effectively making “a matte, non-reflective finish” the
primary standard for reviewing roofing material.
Architectural History:
Mill-sawn wood shingles were by far the most common roofing material in Aspen between 1880 and 1930.
Sanborn Fire Insurance maps from 1886-1904 indicate that “wood” and “shingle” (used interchangeably)
predominated the primary roofs of residential buildings and about half of the commercial buildings. “Slate
or tin” roofs frequently clad secondary roofs, particularly those of porches, additions, and outbuildings.
Photographic evidence from the late 1800s and early 1900s confirm the ubiquity of small, uniform rows, of
smooth wood shingles across the broadest roof planes, and the narrow vertical corrugations or standing
seams of sheet metal on smaller slopes nearer the alleyways. Without material evidence to the contrary,
other roofing material, such as wood shake or ceramic tile, were rarely used, if at all, in Aspen prior to the
1930s. In fact, “DIRT RF.” is a more common annotation on Sanborn maps.
For some architectural styles, roofing material may be a character defining feature. Special consideration
for these structures may be warranted. The “Historic Overview” of the Guidelines identifies a few of these
styles and the roofing materials associated therewith. The Pioneer style (c.1879-1893) of residential
buildings, for instance, had roofs “constructed of readily available material, including canvas, wooden
shingles, and sheet metal.” Among the list of characteristics of Miner’s Cottages (c.1880-1893), however,
the Guidelines include only “shingle roofing.” “Decorative shingles” are a listed characteristic of Queen
Anne-style (c.1880-1893) dwellings in Aspen. Generally,
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Availability:
Accessing homeowner insurance has quickly become the principal obstacle to using wood shingles.
Following anecdotal evidence from the owners of historic properties, staff contacted local insurance
brokers and spoke with the Professional Insurance Agents Association of Colorado to confirm the
industry’s reluctance, if not outright refusal, to underwrite buildings that have wood roofing. Many insurers
make exceptions for their current customers with this “pre-existing condition,” but not for prospective
customers or the installation of new wood materials. The fire resistance rating of the roof assembly does
not matter to the insurance companies. They understand the various supplemental fire-resistive treatments
for wood roofing to be temporary, ineffective over time. Confirming ongoing maintenance and periodic
reapplication of these products on wood roofing is impractical for insurance adjustors compared to the
continuous fire resistive qualities of other roofing materials. So far, staff has found only one company that
will consider new wood roofing in some instances. If the property is in an area of low or moderate fire
danger, this company will consider other mitigating factors that may compensate for the presence of a
wood roof. Otherwise, the secondary or non-standard insurance market may be the only means of insuring
some historic buildings. These policies are roughly five to ten times the price of a standard policy.
Benchmarking:
Every building tells its own story, through its unique character defining features. What may be significant
in one building, may be insignificant in another. This leads to inconsistencies across the historic
preservation community. Solutions to questions about materials, energy efficiency, etc. must be specifically
tailored to the history, climate, and resources of an area, and even further, each building provides a unique
puzzle to understand.
With that being said, benchmarking can assist in making constructive comparisons, and allow us to learn
valuable lessons. Other communities may be entertaining similar questions to Aspen, and though their
solutions may not be a one size fits all approach, understanding the solutions that other communities have
built will help our community weigh the pros and cons of different routes.
Preservation staff at four communities in Colorado (Crested Butte, Telluride, Steamboat Springs, and
Breckenridge) were informed of the upcoming work session in with the City of Aspen HPC regarding wildfire
and insurance concerns in Aspen and how that might translate into updated practice/guidelines for our
historic preservation program, particularly focusing at this time on roofing materials. They were further
informed of the following:
• That the majority of AspenVictorian resources historically had wood shingle roofs on at least the
street facing portion of the building.
• Often rear massing and/or outbuilding had metal roofs.
• Current practice in Aspen allows for the administrative approval of wood shingle or architectural
asphalt shingle for AspenVictorian resources, but other substitute materials require HPC review at
a board hearing.
City of Aspen staff asked the following questions:
• Do you allow or ask for wood shingle at all?
• Do you allow synthetic wood shingles, or even metal, to replace what was historically wood shingle?
o Is this approvable at a staff level?
• Are there any materials you think do a particularly good job in replacing wood shingle?
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• How are you handling concerns about wildfire and/or insurance when it comes to material
requests?
• Just generally, how do you handle roofing material requests that utilize substitute materials?
Crested Butte
A representative from Crested Butte responded, stating that they are undergoing the same process of
evaluating their plan:
We are in the midst of writing our historic preservation plan. Once this is complete, we will
be updating our Standards and Guidelines in 2025 and want to talk through materials from
the WUI code and environmental stewardship perspective.
Their situation is different in that wood shingles were replaced with metal roofs for a large portion of their
historic resource from the 1960’s through to the early 2000’s. However, in instances where wood shakes
or shingles are currently the primary material, practice dictates that they are not replaced with a substitute
material but rather replaced with fire treated wood shingle or shake, as appropriate.
Only one project in Crested Butte has approved what they call an “alternative roofing material.” This
approval occurred around 8 years ago on new construction associated with an accessory building. Please
note that updates in the synthetic shingle market have occurred since this approval. Ultimately on this
decision, the board was not pleased with the outcome, and the material has not been proposed since.
Currently, any synthetic shingle or shake product would require a full board hearing in Crested Butte. One
design guideline that assists with their determination regarding new materials is Design Guideline 4.77:
4.77 New materials may be considered. The material, if approved, will be monitored for 12 months,
and then evaluated for use in other districts/applications. In order to be considered the materials
must meet all the following criteria: (Added 2001, Rev. 2020)
a They must appear similar, initially and over time, to traditional building materials found on
historical buildings of like use. Shadow lines, reveals, texture, joints and joining of the
materials, as well as the finished appearance of the product, may be considered when
determining a material’s acceptability.
b They must have a demonstrated durability in this climate and the ability to be repaired.
c They must demonstrate some advantage over traditional materials with regard to energy
efficiency or resource conservation.
Telluride
Telluride representatives also mentioned that this is a current issue that their community is working
through, and that they as well are revising their guidelines “to allow more updated materials that take into
consideration wildfire and insurance concerns.”
Although they have indicated that many or their historic resources no longer have wood shingle roofs,
Telluride would not permit wood roofs that do still exist to be converted to metal. Their practice is to require
a like-for-like replacement or synthetic wood shingle.
Telluride has approved the use of synthetic wood shingle on their historic train depot, as well as two other
historic structures. The board particularly has been impressed with the DaVinci composite/synthetic
shingle, and the design guidelines are being updated to include synthetic wood shingles as an appropriate
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option based on their commission support. However, a change in materials from wood shingle to synthetic
shingle requires a board level approval.
Steamboat Springs
Steamboat Springs representatives have indicated that most roofs on historic structures in their community
have been replaced with metal roofing over many decades. Due to this, they have adapted their guidelines
for metal and other roof replacements that may vary from original materials. Most roof work in Steamboat
Springs is approved administratively by staff.
Breckenridge:
Staff at Breckenridge indicate that wood shingles were prohibited “a couple of years ago”, and it appears
that Ordinance #23, Series of 2023, titled An Ordinance Prohibiting Wood Shingles on Roofs was passed
on July 25, 2023. Based on their response, the prohibition did not affect many historic projects “as most
were either using composite shingles or metal roofing already.” They allow a variety of roofing materials in
their historic and conservation districts, including composite shingles and low-profile standing seam metal
roofing. They have indicated that their building types are more utilitarian, allowing for more flexibility than
more formal styles.
National Park Service
The National Park Service provides guidance across the United States in historic preservation. Of
particular note to this discussion is the recently updated (2023) Preservation Brief 16: The Use of Substitute
Materials on Historic Building Exteriors, written by John Sandor, David Trayte, and Amy Elizabeth Uebel,
included in Exhibit B. This document provides questions to ask when considering substitute materials
(roofing materials included) and recognizes that flexibility may be warranted in substitute materials for
historic properties in certain cases.
Policy Processes:
Design Guideline Amendment:
The City of Aspen HPC has indicated to staff that they are interested in revising the City of Aspen Historic
Preservation Design Guidelines. Per the Municipal Land Use Code Section 26.220.010.e Powers and
Duties, the HPC has the power to:
To adopt by resolution any operational guidelines or documents that will be used in a
guiding capacity by the Commission. To recommend via resolution adoption of design
guidelines by the City Council. To provide input on Master Plans, in accordance with
Chapter 26.311;
The process for this is outlined in Section 26.310.020 Amendments to the Land Use Code Procedure for
Amendment, particularly of note, the HPC may initiate an amendment (Exhibit X):
The Historic Preservation Commission may initiate an amendment to the Land Use Code.
Initiation shall require the adoption of a Resolution by the Historic Preservation
Commission. The Resolution shall be forwarded to City Council for authorization to
proceed through the process outlined herein. City Council shall determine the extent to
which Step One is required (Steps Two and Three are mandatory).
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If HPC would like to direct staff to initiate the procedure and provide a draft resolution to be forwarded
to City Council, staff does recommend focusing the amendment to the design guidelines on Chapter 7.
Roofs (Exhibit A).
Interpretation/Policy:
HPC should also consider the current design guidelines regarding roofing materials and determine if there
is any flexibility in how they could be interpreted. A policy may be able to be written allowing for flexibility
if HPC agrees on an interpretation.
This may be difficult giving the following guidelines:
7.7 Preserve original roof materials.
• Avoid removing historic roofing material that is in good condition. When
replacement is necessary, use a material that is similar to the original in both
style as well as physical qualities and use a color that is similar to that seen
historically.
7.8 New or replacement roof materials should convey a scale, color and texture
similar to the original.
• If a substitute is used, such as composition shingle, the roof material should be
earth tone and have a matte, non-reflective finish.
• Flashing should be in scale with the roof material.
• Flashing should be tin, lead coated copper, galvanized or painted metal and have
a matte, non-reflective finish.
• Design flashing, such as drip edges, so that architectural details are not
obscured.
• A metal roof is inappropriate for an Aspen Victorian primary home but may be
appropriate for a secondary structure from that time period.
• A metal roof material should have a matte, non-reflective finish and match the
original seaming.
7.9 Avoid using conjectural features on a roof.
• Adding ornamental cresting, for example, where there is no evidence that it
existed, creates a false impression of the building’s original appearance, and is
inappropriate.
As we have seen in past presentations, many synthetic shingles replicate shake rather than shingle,
not quite replicating wood shingle in size, texture, or color, and the material has a slight reflective
sheen.
Goals:
• Identify the issue(s).
• Identify what, if anything, the HPC can and/or should do to address it.
• If desired, choose a process by which to proceed.
• Plan next steps.
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Questions to answer:
• What is/are the fundamental issue(s) related to roofing materials the HPC wants to address?
• How would HPC like to proceed?
• Would HPC like any additional information?
• What type of roofing requests would HPC like to see as administrative and what would they like to
see at a full board hearing?
Exhibits
Exhibit A: “Chapter 7: Roofs.” City of Aspen Historic Preservation Design Guidelines. Revised 2016.
Exhibit B: Preservation Brief 16: The Use of Substitute Materials on Historic Building Exteriors.
Revised 2023. John Sandor, David Trayte, and Amy Elizabeth Uebel.
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68 • City of Aspen • Historic Preservation Design Guidelines
cHapter 7: rooFs
Background
The character of the roof is a major feature for most
historic structures. In each case, the roof pitch,
materials, size and orientation are all distinct features
that contribute to its character. Aspen Victorian
properties have a range of gabled, hip, shed, and flat
roof forms depending on building type. AspenModern
properties typically have a range of gable, parabolic,
butterfly or flat roof forms depending on the
architectural style. Although the function of a roof is
to protect a structure from the elements, it contributes
to overall architectural character of the building.
Characteristics Most Associated with Aspen
Architectural Styles
• Deep Overhangs - Chalet, Modern Chalet, Rustic,
Wrightian
• Flat roof, minimal eaves - Modern
• Gables, shed - Victorian
Deterioration
The roof is the structure’s main defense against the
elements. Over time all components of the roofing
system are vulnerable to leaking and damage. When
the roof begins to experience failure it can affect other
parts of the structure by no longer acting as a barrier
from water, wind, and exposure. Common sources of
roof leaks include:
• Cracks in chimney masonry
• Loose flashing around chimneys and ridges
• Loose or missing roof shingles
• Cracks in roof membranes caused by settling
rafters
• Water backup from plugged gutters
• Ice dams
Policy: The character of a historical roof,
including its form and materials, should be
preserved.
c HApter 7: roofs
Deep overhangs on a Chalet.
An A-Frame roof form on a Fritz Benedict designed home.
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City of Aspen • Historic Preservation Design Guidelines • 69
cHapter 7: rooFs
Repairing a Historic Roof
When repairing a historic roof it is important to
preserve its historic character. It is not appropriate
to alter the pitch of a historic roof, or to change the
orientation of the roof to the street. Eave overhangs
are extremely important to the style of the house and
should be preserved.
Gutters, Downspouts, Snowstops, and Snow
Fences
Gutters and downspouts are used to divert water
away from a structure. Without this drainage system,
water may splash off the roof onto exterior walls and
run along the foundation of the building. Snowstops
and snow fences are used to protect inhabitants and
the building from the sudden snow avalanches that
rip off architectural details and can cause serious
injury. Gutters can be seen in some 19th century
photos of historic buildings and are more common on
AspenModern structures. Overall, the visual impact
of these functional elements should be minimized.
Dormers
Historically, a dormer was sometimes added to create
more head room and light in an attic. It typically had
a vertical emphasis and was usually placed as a
single element or in a pair on a roof. A dormer did not
dominate a roof form. A new dormer should always
read as a subordinate element to the primary roof
plane. A new dormer should never be so large that
the original roof line is obscured. It should also be set
back from the roof edge and located below the roof
ridge. In addition, the style of the new dormer should
be in keeping with that of the building. Dormers are
generally foreign to some architectural styles, such
as Modernism.
Roof Materials
Exterior roof materials like shingles are usually not
original on Aspen Victorian properties due to age
and replacement over time. Periodic replacement
of roofing is accepted. However, roof sheathing
and structure is typically original on most of these
buildings should be preserved. When repairing or
altering a historic roof, do not remove significant
materials that are in good condition. Always repair
materials when feasible. For example, sister beams
when roof rafters need more structural integrity
rather than removing and replacing the element.
Where replacement is necessary, use a material that
is similar to the original in style and texture. Some
AspenModern styles exposed roof rafters under deep
overhangs as part of the architectural style. These
character defining features must be preserved.
Preserve original roof cresting, as found on the Sardy House.
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70 • City of Aspen • Historic Preservation Design Guidelines
cHapter 7: rooFs
Additions to Roofs
Many Aspen residences have original chimneys.
Wood burning appliances are no longer allowed in the
City of Aspen, which means that historic chimneys
are being retrofitted to accommodate other vents.
New venting of any type added to a roof should be low
profile, carefully located, and painted a matte black or
dark color to not detract from the historic chimney.
Treatment of Roofs
7.1 Preserve the original form of a roof.
• Do not alter the angle of a historic roof. Preserve
the orientation and slope of the roof as seen from
the street.
• Retain and repair original and decorative roof
detailing.
• Where the original roof form has been altered,
consider restoration.
7.2 Preserve the original eave depth.
• Overhangs contribute to the scale and detailing of
a historic resource.
• AspenModern properties typically have very deep
or extremely minimal overhangs that are key
character defining features of the architectural
style.
7.3 Minimize the visual impacts of skylights
and other rooftop devices.
• Skylights and solar panels are generally not
allowed on a historic structure. These elements
may be appropriate on an addition.
7.4 New vents should be minimized, carefully,
placed and painted a dark color.
• Direct vents for fireplaces are generally not
permitted to be added on historic structures.
• Locate vents on non-street facing facades.
• Use historic chimneys as chases for new flues
when possible.
7.5 Preserve original chimneys, even if they
are made non-functional.
• Reconstruct a missing chimney when
documentation exists.
7.6 A new dormer should remain subordinate
to the historic roof in scale and character.
• A new dormer is not appropriate on a primary,
These new chimney vents are consistent with the building
type, located behind the ridgeline, and a dark color.
This non-historic chimney is overscaled for the miner’s
cottage.
Before: Skylights are inappropriate on a miner’s cottage.
After: The historic resource after the skylights were removed.
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City of Aspen • Historic Preservation Design Guidelines • 71
cHapter 7: rooFs
character defining façade.
• A new dormer should fit within the existing wall
plane. It should be lower than the ridgeline and set
in from the eave. It should also be in proportion
with the building.
• The mass and scale of a dormer addition must be
subordinate to the scale of the historic building.
• While dormers improve the livability of upper floor
spaces where low plate heights exist, they also
complicate the roof and may not be appropriate
on very simple structures.
• Dormers are not generally not permitted on
AspenModern properties since they are not
characteristic of these building styles.
Materials
7.7 Preserve original roof materials.
• Avoid removing historic roofing material that is in
good condition. When replacement is necessary,
use a material that is similar to the original in both
style as well as physical qualities and use a color
that is similar to that seen historically.
7.8 New or replacement roof materials should
convey a scale, color and texture similar to the
original.
• If a substitute is used, such as composition
shingle, the roof material should be earth tone and
have a matte, non-reflective finish.
• Flashing should be in scale with the roof material.
• Flashing should be tin, lead coated copper,
galvanized or painted metal and have a matte,
non-reflective finish.
• Design flashing, such as drip edges, so that
architectural details are not obscured.
• A metal roof is inappropriate for an Aspen
Victorian primary home but may be appropriate
for a secondary structure from that time period.
• A metal roof material should have a matte, non-
reflective finish and match the original seaming.
7.9 Avoid using conjectural features on a roof.
• Adding ornamental cresting, for example, where
there is no evidence that it existed, creates a false
impression of the building’s original appearance,
and is inappropriate.
Before: A historic resource before dormers were added.
After: New dormers that are too large can change the massing
of the original building.
Preserve original roof material when possible.
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cHapter 7: rooFs
7.10 Design gutters so that their visibility
on the structure is minimized to the extent
possible.
• Downspouts should be placed in locations that
are not visible from the street if possible, or
in locations that do not obscure architectural
detailing on the building.
• The material used for the gutters should be in
character with the style of the building.
These simple gutters are in character with a miner’s cottage.
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PRESERVATIONBRIEFS16
The Use of Substitute Materials
on Historic Building Exteriors
John Sandor, David Trayte, and Amy Elizabeth Uebel
The Secretary of the Interior's Standards for Rehabilitation
generally require that deteriorated distinctive architectural
features of a historic property be repaired rather than
replaced. Standard 6 of the Standards for Rehabilitation
further states that when replacement of a distinctive
feature is necessary, the new feature must “match the old
in composition, design, color, texture, and other visual
properties, and, where possible, materials” (emphasis
added). While the use of matching materials to replace
historic ones is always preferred under the Standards for
Rehabilitation, the Standards also purposely recognize
that flexibility may sometimes be needed when it comes
to new and replacement materials as part of a historic
rehabilitation project. Substitute materials that closely
match the visual and physical properties of historic
materials can be successfully used on many rehabilitation
projects in ways that are consistent with the Standards.
The flexibility inherent in the Standards for Rehabilitation
must always be balanced with the preservation of the
historic character and the historic integrity of a building,
of which historic materials are an important aspect.
Any replacement work reduces the historic integrity of
a building to some degree, which can undermine the
historic character of the property over time. With limited
exceptions, replacement should only be considered when
damage or deterioration is too severe to make repair
feasible. When needed replacement is made with a
material that matches the historic material, the impact
on integrity can be minimal, especially when only a small
amount of new material is needed. When a substitute
material is used for the replacement, the loss in integrity
can sometimes, although not always, be greater than
that of a matching material. Also, whether historic or
substitute material, there is a point where the amount
of replacement can become excessive and the building’s
historic integrity is diminished to an unacceptable
degree, regardless of the material used—that is, a loss of
authenticity and the physical features and characteristics
closely associated with the property’s historic significance.
National Park Service
U.S. Department of the Interior
Technical Preservation Services
The term substitute materials is used to describe building
materials that have the potential to match the appear-
ance, physical properties, and related attributes of historic
materials well enough to make them alternatives for use
in current preservation practice when historic materials
require replacement.
Compelling reasons to use a substitute material instead
of the historic material include the unavailability or poor
performance of the historic material, or environmental
pressures or code-driven requirements that necessitate a
change in material. When using a substitute material for
replacement it is critical that it match the historic material
in all of its visual and physical properties to preserve the
historic character of the building and minimize the impact
on its integrity.
Substitute materials can be cost-effective, permit the ac-
curate visual duplication of historic materials, and provide
improved durability. While the behavior of traditional, his-
toric materials is generally well understood, the behavior
of newer materials can be less established and sometimes
less predictable. Substitute materials are most successful
when the properties of both the original material and the
substitute are thoroughly understood by all those involved
in the design and construction process. The architect must
be adept at the selection of substitute materials and their
incorporation into architectural plans and specifications.
The contractor or tradesperson in the field must also be
experienced with their use.
This Preservation Brief provides general guidance on the
use of substitute materials as replacement materials for
distinctive features on the exterior of historic buildings.
Due to the ever-evolving product market for construction
materials, this Brief does not provide specifications
for substitute materials. This guidance should be used
in conjunction with qualified professionals who are
knowledgeable in current construction and historic
preservation practices.
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Substitute Materials and
Applying the Standards for
Rehabilitation
The Standards for Rehabilitation are focused on
preserving the important and distinctive
character-defining features of a historic property
(Standards 2 and 6), and they are to be applied in a
reasonable manner, taking into account economic
and technical feasibility (36 CFR 67.7 and 36 CFR
68). The Standards have an inherent flexibility that
facilitates their application to diverse projects,
historic properties, and conditions. They are to
be applied on a “cumulative-effect” basis, when
the overall effect of all work in the context of the
specific conditions of the property and the project is
consistent with the property's historic character.
The Standards for Rehabilitation require that the
replacement of a distinctive feature match the old
in physical and visual properties. While the use of
matching materials is always preferred, the Standards
purposely allow for the use of substitute materials
when the use of original materials is not reasonably
possible, such as in consideration of economic and
technical feasibility or in new construction. They
also provide additional flexibility in the treatment
of secondary, less distinctive features that are
less important in defining the historic character
of the property. The Standards for Rehabilitation
recognize that flexibility is appropriate to facilitate
“a compatible use for a property … while preserving
those portions or features which convey its historical,
cultural, or architectural values” (definition of
“Rehabilitation,” 36 CFR 67.2(b)).
This Brief includes a discussion of the appropriate use
of substitute materials and provides a path for decision-
making in their use. In considering the use of substitute
materials, such issues as the deterioration or failure of
the historic building component and material must be
understood. The existing component’s physical and visual
properties, profile, surface texture, dimensions, and
performance should be identified to establish the basis for
evaluating a possible replacement material. The physical
and visual properties of the various substitute materials
available should also be assessed and compared to the
original material for their physical and visual compatibility.
Lastly, the suitability of a given substitute replacement
material should be determined based on how well the
material matches both the physical and visual properties
of the existing material as well as any specific performance
or application needs. The Brief’s descriptions of common
substitute materials are not meant to be comprehensive,
and, as the performance history of newer materials
continues to grow and new materials are developed,
available options will change, and our understanding of
current material performance will continue to evolve.
Historical Use of Substitute
Materials
The tradition of using affordable and common materials
in imitation of more expensive and less available materi-
als is a long one. At Mount Vernon, for example, George
Washington used wood painted with sand- impregnated
paint to imitate rusticated stone. This technique, along
with scoring stucco into block patterns, was common in
Colonial America to imitate stone.
Nineteenth-century technology made a variety of materi-
als readily available and widely used that were not only
able to imitate traditional materials but were also cheaper
to fabricate and easier to use. Traditionally, carved stone
units were individually worked. Molded or cast materials
greatly increased efficiency in creating repetitive ele-
ments. Cement-based products such as cast stone could
provide convincing imitations of natural stone with care -
fully chosen aggregates and cements and was typically a
commercially manufactured product. It could be tooled
like natural stone, though that could reduce much of
the cost advantage. These carefully-crafted cementitious
products were widely used as trim elements for masonry
structures or as the face material for an entire building.
At the other end of the spectrum, mail-order catalogs
provided a wide variety of forms for molding concrete
that were merely evocative of natural stone and did little
to match its appearance. Concrete masonry units could be
fabricated locally and on site, avoiding expensive quarry-
ing and shipping costs.
Offering similar efficiencies as cast stone for reproducing
repetitive and even complex decorative shapes, terra cotta
could mimic the surface characteristics of stone with vari-
ous textures and glazes. It was popular in the late nine -
teenth and early twentieth centuries for details on stone
or brick buildings as well as for the entire skin of large and
elaborately detailed buildings.
Cast iron was also used to imitate stone, often with very
decorative profiles, for a variety of architectural features
ranging from window hoods to columns, piers, balus-
trades, and even whole façades. Cast iron offered its own
set of efficiencies including cost, fabrication time, and
weight, but required a painted finish.
While cast stone, terra cotta, and cast iron offered effi-
ciencies over quarried and, particularly, carved stone, they
were not cheap or impermanent materials. Less costly, but
also less durable, stamped or brake-formed sheet metal,
typically galvanized, could also be used instead of masonry
for cornices, window hoods, roofing tiles, and even entire
building façades.
14
3
Examples of Historical Use of Substitute Materials
Figure 2a. Casting concrete blocks to mimic quarried
stone was a popular late 19th- to mid 20th-century
technique. Concrete masonry units could be completed by
local craftsman, saving time and shipping costs.
Photo: John Sandor, NPS.
Figure 2b: The 19th century also produced a variety of
metal products used to imitate other materials. Across the
country, cast iron was used in storefronts to imitate stone.
Photo: John Sandor, NPS.
Figure 2c: Stucco has been used to imitate a number of
building materials for many centuries. Seen here, stucco
was applied to a brick structure and scored to represent a
stone façade. Photo: John Sandor, NPS.
Figure 2d: Terra cotta gained popularity in the late 19th
century as a cheap and lightweight alternative to stone.
Glazing techniques allowed the blocks to imitate a variety
of natural stone materials. Photo: John Sandor, NPS.
15
4
These examples of one material used to imitate another,
more often in initial construction than for later repair and
replacement purposes, are referred to as imitative materi-
als in the Guidelines for Preserving, Rehabilitating, Restor-
ing & Reconstructing Historic Buildings, updated in 2017,
that accompany the Secretary of the Interior's Standards
for the Treatment of Historic Properties. These imitative
materials, while evoking other materials, usually had dis-
tinctive qualities of their own and were not always a very
close match in appearance to the historic material they
were meant to imitate.
Many of the traditional materials discussed above are still
available and used to replace damaged or missing original
features, both to replace matching historic materials and
sometimes as substitute materials. Because of their exten-
sive use over time and their known physical and chemical
properties, cast stone, cast iron, and terra cotta are well
understood substitute materials. This continued usage
and familiarity means their installation requirements and
service life are well established, which in turn makes it
easier to determine when and how to use these traditional
materials as substitutes for a deteriorated material. Howev-
er, innovation in replacement materials continues, and new
products (many of them consisting of synthetic materials)
are continually introduced. These non-traditional products
are an increasing part of both the new construction and
rehabilitation industries. Some materials, like glass fiber
reinforced polymers, glass fiber reinforced concrete, or
fiber cement, have been in use long enough for an accu-
rate prediction of their service life and performance. Other
newer, non-traditional materials may be too new to have
established performance records, thus, understanding
their material properties is critical, and their use should be
approached with more caution.
When to Consider Using Substitute
Materials in Preservation Projects
According to the Standards for Rehabilitation, deteriora-
tion should generally be addressed through repair if in
repairable condition. Repair can entail a variety of treat-
ments that retain the unit of building material and remove
and patch or replace only the damaged portion. This ap -
proach can be done with traditional methods and materi-
als such as a dutchman, where like-kind material is pre-
cisely inserted into wood or stone, or it may employ other
materials such as epoxies for wood repair or cementitious
compounds for masonry. As long as the repair methods are
sound and do not damage or accelerate the deterioration
of the historic material, repairs are generally preferable to
replacement of an entire element. More complex manufac-
tured products, typical of more recent historic materials (as
well as a lot of modern building materials generally), may
be more difficult to repair, if they can be repaired at all.
There are situations, however, when the level of deterio-
ration makes localized repairs infeasible and entire fea-
tures or units of historic material must be replaced. While
achieving an effective match of all of the visual qualities of
a material can be challenging, even when replacement is
in kind, it can be even more challenging when the replace-
ment is a substitute material. A good visual match is not
the only consideration when a substitute material is to be
used for incremental replacement within a larger assem-
bly of historic material. When an individual siding board
or a single block of ashlar is being replaced, it is usually
best achieved with the original material. Introduction of
a different material into an intact assembly requires that
its inherent properties, such as expansion and contraction,
moisture resistance, or permeability, be thoroughly consid-
ered relative to those of the surrounding historic materials
to avoid causing damage.
Figure 3: Incremental repair is best done using in-kind material to
minimize differences in the performance characteristics that could
negatively affect the overall assembly. Photo: NPS.
Figure 4. While occasionally used to imitate other materials such as
wood or slate shingle, many asbestos shingles and siding materials
had their own distinct shape and profile. No longer manufactured
today, alternative materials must be found to replace these
materials when they are distinctive features on a historic structure.
Drawing: Association for Preservation Technology, Building
Technology Heritage Library.
16
5
Circumstances in which the use of substitute materials
may generally be considered appropriate, taking into
consideration technical and economic feasibility reasons,
include: the unavailability of historic materials; the
unavailability of skilled artisans or historic craft techniques;
inadequate durability of the original materials; the
replacement of a secondary feature; construction of a
new addition; the reconstruction of a missing feature;
code-required performance; and for enhanced resilience
and sustainability:
• Unavailability of historic material. A common
reason for using substitute materials is the difficulty
in finding a good match using the historic material
(particularly a problem for masonry materials where
the color and texture are derived from the material
itself). This may be due to the actual unavailability
of the material or to protracted delivery dates,
particularly if the material cannot be sourced
domestically. It is not uncommon for a local quarry
that is no longer in operation to have been the source
of an original stone. If another quarry cannot supply
a satisfactory match, a substitute material such as dry-
tamp cast stone or textured precast concrete may be
an appropriate alternative, if care is taken to ensure
that the detail, color, and texture of the original
stone are matched. Even when the color is successfully
matched, the appearance of a cementitious product
may diverge from that of the historic stone as the
substitute material ages.
Many manufactured materials that were used
historically on buildings are no longer made. Terne-
plated steel, which was the material most typically
used for painted standing-seam or flat-seam roofing,
is no longer made. However, because it was always
painted, other metals including galvanized steel or
copper can generally be substituted if painted. When
the historic material needing to be replaced is a
manufactured product developed as an imitation of
a natural material, which was the case with asbestos
shingles meant to imitate slate, the natural material
may now be an appropriate substitute material to
consider for the manufactured one that is no longer
produced.
• Unavailability of skilled artisans or historic
craft techniques. These two issues can complicate
any preservation or rehabilitation project. This is
particularly true for intricate ornamental work, such
as carved wood, carved stone, wrought iron, or cast
iron. While skilled craftsmen may not be as difficult
to find as they once were, there can still be limitations
geographically, even in finding less specialized skills,
and particularly if a project is small. Technical advances
have allowed some stone or wood carvers to take
advantage of computerized equipment, but complex
designs will likely still require hand work. It may
also be possible to mimic a carved element using a
material that can be cast in a mold, adding significant
efficiency where an historic element survives from
which a mold can be made. Options for casting include
aluminum, cast stone, fiberglass, glass fiber reinforced
concretes, and terra cotta, but not all carved elements
can be duplicated by a casting, and mold-making and
casting still require skilled craftsmen.
• Inadequate durability of the original material.
Some historic building materials were of inherently
poor quality or were not durable. In other cases,
one material was naturally incompatible with other
materials on the building, causing staining or galvanic
corrosion. Examples of poor-quality materials are
very soft sandstones, which eroded quickly, and
brownstone, which is vulnerable to delamination.
In some cases, more durable natural stones may be
visually similar enough to stand in for these soft stones
but cast stone or another material may be needed to
achieve an appropriate match.
Figure 5. (Left) Asbestos shingles were often used as a substitute for traditional slate roof shingles. The historic asbestos roof on this rehabilitation
project had reached the end of its lifespan and required complete replacement. (Right) Given the limited replacement materials available to match
the historic asbestos shingles, utilizing natural slate was determined to be the best visual match for the original shingles and design intent in this
instance. Photos: Crosskey Architects.
17
6
Figure 6. The dramatic
difference in the number
of growth rings between
old-growth wood and
wood that was recently
harvested from second-
or third-growth forests
is indicative of the
diminished dimensional
stability and durability
of most lumber currently
available. Photo:
Zachary Dettmore.
The ready availability of manufactured ornamental
wood features fed a nineteenth-century taste for
decorative architectural details that were often
used on the exterior of buildings with little concern
for how they would be affected by moisture or
maintained. Even old-growth wood from decay-
resistant species often could not prevent features
with severe exposure from eventually needing to be
replaced. Today’s available commercial supplies of
lumber no longer provide the denser, more decay-
resistant wood of old-growth forests, so even careful
matching to species, which is not always possible, will
not yield a replacement equal in performance to the
historic material. Old-growth wood is likely to be very
expensive, if it can be found, and may not be available
from a sustainable, environmentally responsible
source. When features with severe exposure need to
be replaced or reproduced, substitute materials that
are less susceptible to decay can have a longer life, and
when the feature is painted, as exterior wood features
generally are, the visual effect of a substitute material
can be minimal.
• Replacement of a secondary feature. When it
is necessary to replace a less distinctive, secondary
feature that is less important in defining the historic
character of the property, there is more flexibility in
how it can be replaced. While it may be less important
to find an exact match in materials when replacing
such a feature, the retention of the overall historic
character should still guide selection of an appropriate
replacement material. For example, replacing
secondary features such as those with limited visibility
(e.g., siding materials on a rear elevation) may permit
replacement materials that are similar in appearance
or character without having to be a perfect match.
• Construction of a new addition. The Standards
require that new additions to historic buildings and
related new construction be differentiated from the
old as well as be compatible with the historic character
of the property and its site and environment. Using
materials that evoke, without matching, the historic
material can be an effective means of achieving
the needed balance between compatibility and
Figure 7. A new addition replaced non-historic construction on the rear elevation of this building. Fiber cement gives the addition a compatible
appearance without replicating the exposure for thickness of the historic siding. Photo: Ward Architecture + Preservation.
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7
Figure 8. A long-missing cast-iron steeple was reconstructed in aluminum and
fiber-reinforced polymer (FRP). Photo: John Sandor, NPS, Inset: Quinn Evans.
differentiation for new additions and
new construction. Even if differentiation
is achieved through design rather than
materials, there generally is no basis for
requiring the use of matching historic
materials for new additions and new
construction as part of a rehabilitation
project.
• Reconstruction of a missing feature.
Many buildings lose significant features
over the course of their lives for reasons
such as those previously discussed. When a
missing feature is to be reconstructed, the
importance of matching the original mate-
rial may be less important to the effect
replacing the missing feature may have on
the overall historic character and appear-
ance of the building. Though replacement
of missing features must be substantiated
by documentary, physical, or pictorial
evidence, in many cases the authenticity
of the material may be secondary to the
overall visual qualities. The use of a more
cost-effective substitute material for the
construction of a missing feature can often
be an important factor in the feasibility of
undertaking such work.
• Code-required performance.
Modern building codes are regularly
amended to require higher performance
levels for new and existing buildings in such
areas as life safety, seismic retrofits, and
accessibility. Rehabilitation projects often
trigger compliance with code requirements
that were not in place when a building
was constructed. Although building codes
may often allow for the retention of
historic materials and assemblies, substitute
materials can offer an alternative in
situations when the historic materials are
non-compliant and cannot otherwise be
reasonably retained. In these instances, a
change in material may be appropriate to
meet code requirements, while in other
instances selecting the optimal code
compliance method for the project may
achieve code-compliant solutions that also
allow for the preservation of a building’s
historic materials and finishes.
For example, fire codes may require
increased resistance to flame spread for
buildings within dense urban environments
where building proximity and separation
between buildings is a concern. Some
substitute materials are non-combustible,
have good ratings for flame spread, and
can provide an alternative to help meet
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8
fire code requirements. Depending on the building
component and the material, however, a substitute
material may not resist fire any better than the
historic material. In addressing code issues, all feasible
alternatives should be considered to minimize the
impact on the historic character of the building while
still meeting code requirements.
With specific provisions in building code related to
issues such as seismic hazards, the choice of materials
for features inherently unstable in a seismic event can
be a key part of a code-compliant retrofit solution.
Elements at risk of falling such as parapets, finials, and
overhanging cornices may be made safe by anchoring
them to new structural frames. However, for some
heavy masonry features, especially where there is
deterioration or the feature is difficult to effectively
brace, adequately anchoring the existing feature
may not prove feasible. In such cases removing and
replacing these features with lighter-weight replicas
that incorporate a resilient structural framework can
help preserve the historic character of the building
while improving life safety performance.
• Enhanced resilience and sustainability. Wildfires,
earthquakes, floods, hurricanes, and other extreme
weather events put historic buildings and their occu-
pants at risk and may require adaptive treatments that
are more invasive than might be accepted in other cir-
cumstances, including related to the use of substitute
materials. In these contexts, it is still necessary to try
to minimize impacts on a building’s historic character
as much as possible while still adapting it to be more
resilient. Widespread wildfires, for example, have
increased demand for fire resistant materials for the
exterior building envelope. Flood events may neces-
sitate the replacement of historic materials that have
been damaged or inundated with hazardous substanc-
es in contaminated floodwaters. When undertaking
repairs in such circumstances, substitute materials may
offer greater resilience to anticipated future exposure
to natural hazard risks.
Similarly, efforts to improve energy efficiency and
performance may include the use of substitute materi-
als as replacement components when modifications to
building assemblies are required and the historic mate -
rials cannot be preserved. When evaluating substitute
materials in the context of sustainability objectives,
factors such as the environmental impact of produc-
tion, the full life cycle of products, and the embodied
carbon of the materials already in place should be
carefully analyzed. There may be more sustainable
choices for a replacement material, including the use
of more traditional materials in place of manufactured
products that may consist of non-renewable resources
or hazardous materials. While some synthetic substi-
tute materials are made from recycled materials or
are otherwise sustainably produced, many are not
repairable, salvageable, or recyclable themselves, and
they may have shorter lifespans to their historic mate-
rial counterparts. When either greater resilience or
sustainability is a factor, all feasible alternatives should
be considered in finding a balanced approach that
maintains historic character while meeting resilience
and sustainability goals.
Substitute Materials and
Economic Feasibility
Economic feasibility is inevitably a concern when choosing
a material for any part of a project, whether a historic
or substitute material, but it should not be the sole
determinant factor at the expense of maintaining the
Figure 9. Previously bricked-in openings below the flood line were
reopened and new aluminum windows installed with cellular
PVC trim detailed to hold back moderate flood waters and survive
exposure to water. Photo: John Sandor, NPS.
historic character and historic integrity of a building. Other
factors may prompt the consideration of a substitute
material, such as the cost of maintaining the historic
material, because it is comparatively difficult or costly to
reach or access, or the frequency of required maintenance
the historic material needs. Additionally, where in-
kind replacement material is found to be prohibitively
expensive, it may be reasonable to consider a substitute
that offers an alternative and is a good physical and
visual match. Not all substitute materials are, however,
cost-effective replacements. Long-term durability and
maintainability are other factors that should be considered
in conjunction with initial cost.
Maintenance of a material, particularly where accessibil-
ity is difficult or expensive, can be an important part of a
20
9
Figure 10. Polymer slates
offer a choice of shapes but
not sizes, limiting their
ability to achieve a good
visual match for some
historic slate. With the size
of the polymer slates (right)
being nearly twice that of
the historic slates (left), the
scale of the entire feature is
incompatibly altered. The
molded edges of this mate-
rial, which contribute to its
ability to replicate slate,
would be lost if each shingle
was resized by cutting.
Photo: John Sandor, NPS.
cost evaluation. Maintenance costs should not be consid-
ered without also considering life-cycle expenses. While
some substitute materials may offer reduced initial costs,
they may be as or more costly than traditional materials to
maintain over time. For example, many substitute materials
are not readily repairable, necessitating full replacement
when damaged. The cost to replace a material or assem-
bly at the end of its lifespan may also be greater than the
accumulated incremental expense to maintain the historic
material, particularly if it is a more traditional, repairable
material. Maintenance cost should never be the sole reason
for replacing a historic material that is not deteriorated.
Criteria for the Appropriate Use
of Substitute Materials
Substitute materials must meet three basic criteria to be
considered: they must be compatible with the historic
materials in appearance; their physical properties must be
similar to those of the historic materials, or the materials
must be installed in a manner that tolerates differences;
and they must meet certain basic performance expecta-
tions over an extended period of time.
• Matching the Appearance of the Historic
Material
Any material’s appearance varies depending on the
nature of the material and how it is used. Some
historic materials, such as wood and ferrous metals,
were typically painted, making the color of the
substitute unimportant, though the texture of the
surface, which telegraphs through a paint layer, is
still an important consideration. Texture can be a
large part of distinguishing a material formed by
hand from one that is machine-made. Many historic
materials, such as most building stones, are used
without any coating, making the color, pattern, and
reflectivity, as well as surface texture, dependent on
the material itself. Matching the color and surface
characteristics of a historic natural material with a
man-made substitute can often be quite difficult.
When the color and surface characteristics of
an existing material are important, cleaning the
material should be the starting point for evaluating
a potential matching material. In situations where
there are subtle variations in color and texture
within the original material, the substitute
material should be similarly varied so that it is not
conspicuous by its uniformity. If a material is custom
fabricated, a sufficient number of samples should
be supplied to permit on-site comparison of color,
texture, detailing, and other critical visual qualities.
For a manufactured product with preset choices
of color or texture, it may be necessary to look at
samples from more than one manufacturer to find
the best match. Similarly, prefabricated products,
such as roofing slate, may offer limited, if any,
choice of unit size, which can be a critical factor
for achieving a good match. A substitute material
should not be used to replace distinctive, character-
defining materials and features if an adequate
match in design and appearance is not possible.
As all exposed materials are subject to ultraviolet
degradation, samples of a new material, particularly
when custom formulated, should be prepared
during the early planning phases to allow for
evaluation of the effects of weathering on
color stability. When that is not possible, or if a
prefabricated product is used, the fabricator or
manufacturer may be able to identify regional
locations where equivalent products have been
installed long enough ago to get a better sense of
how the material weathers and performs.
While a perfect match is the desired goal for
replacing distinctive features, it is not always
possible, even when the same matching material is
chosen for the replacement. When any compromise
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10
must be made in the precision of the match, it is
wise to consider the vantage point from which
the material will be seen. Sometimes what seems
important at close range, such as variations in the
texture of a surface, may be secondary to other
aspects of the material when viewed from some
distance. The closer a feature is to the viewer, the
more closely the material and craftsmanship should
match the original. An on-site mock-up using a
sample of the proposed material can help evaluate
whether it is an adequate visual match.
• Matching the Physical Properties of the
Historic Material
Carefully chosen substitute materials can often
closely match the appearance of historic materials,
but their physical properties may differ greatly. These
differences are most critical when incrementally
replacing components of a larger assembly that retains
significant historic material. The chemical composition
of the material (e.g., the presence of acids, alkalis,
salts, or metals) should be evaluated to ensure that
the replacement materials will be compatible with the
adjacent historic materials. Materials that will cause
galvanic corrosion or other chemical reactions must be
isolated from one another.
The thermal- and moisture-driven expansion and
contraction coefficients of each adjacent material
must be within narrow limits or be accommodated
by carefully designed joints and fasteners. Joints
can play a role both in accommodating movement
of materials as well as in managing moisture, either
to keep it from entering the enclosure assembly or
to let it escape from the building envelope, or both.
Because some synthetic materials are less permeable
to moisture than more traditional materials,
installations must take into account the potential
to trap moisture and cause deterioration of historic
and new materials. An assembly incorporating new
and historic materials should be designed so that if
material failures occur, the failures occur within the
new material rather than the historic one.
During installation, surface preparation is critical to
ensure proper attachment. Deteriorated underlying
material must be removed or stabilized. Non-
corrosive anchoring devices or fasteners that are
designed to carry the new material and to withstand
wind, rain, snow, and other destructive elements
should be used. Since physical failures often result
from poor anchorage or improper installation
techniques, a structural engineer should be
included in planning any major project. For readily
available, off-the-shelf materials, manufacturers’
recommendations for attachment and spacing should
be followed.
Nearly all substitute materials have some properties
that are different from the historic materials they
may replace. Even when substitute materials are
isolated from historic materials and features, it is
important to understand the substitute materials’
properties in order to use them successfully.
• Performance of the Material Over Time
When more traditional materials are used to replace
damaged historic materials and features, their perfor-
mance is predictable in most cases. An exception may
be modern wood that has durability and other prop-
Figure 11. The thickness of the wood siding on the front (left)
creates a deeper shadow line than is achieved with the fiber cement
siding used on the side (right) elevation. While the exposure can
be adjusted, fiber cement siding is not available in a matching
thickness. Photo: John Sandor, NPS.
Figure 12. Cellulose composite materials, like wood, expand and
contract with moisture. Here it was used to reconstruct a missing
storefront. Unlike solid wood that is dimensionally stable parallel to
the grain, this composite moves equally in all dimensions, resulting
in gaps that were not adequately anticipated in the design.
Photo: John Sandor, NPS.
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11
Figure 13. Cast stone was used to effectively replace individual blocks of sandstone. Both the original ( left) and the substitute material (right)
retain similar physical and visible properties. Having weathered for over 30 years, some erosion of the binder has revealed quartz grains of
the aggregate (inset), but it is only noticeable upon close inspection. Photo: John Sandor, NPS.
erties different than those of historic wood from old-
growth forests. Many of the materials used as substi-
tutes have been in use long enough to provide some
idea of how they perform over time. Other material
may only have test results from accelerated weather-
ing. The length of manufacturer warranties may be an
indicator of expected durability and lifespan. War-
ranties only predict a manufacturer’s expectation of
a product’s performance and are no guarantee that
the manufacturers will still be in business at the time
needed to stand behind them. Just as new manufac-
turers emerge with new materials, others disappear.
Where possible, projects involving substitute materi-
als in similar installations and exposures should be
examined before selecting a new, less-tested material.
It is unrealistic to expect a substitute material, which
can be quite different in composition than the historic
material, not to age differently.
Even traditional materials will not perform well if
not used or detailed appropriately, and experienced
architects, engineers, fabricators, and installers rely
on their professional knowledge and experience to
ensure proper installation and techniques when work-
ing with familiar materials. This is just one of many
reasons that using the original materials for needed
replacement is usually the best choice. Some of the
materials now available as substitutes have properties
that differ greatly from the traditional materials they
may be used to replace. It is critical to the successful
performance of substitute materials that everyone
involved in the selection, design, and installation fully
understands the material’s properties, especially how
it is different than the material it is replacing, and
how that will affect the surrounding materials and
building systems.
Many traditional building materials can be repaired
either with traditional methods and materials or with
more modern conservation techniques using sub-
stances like epoxies. However, many modern substitute
materials (particularly synthetic ones) are not as easily
repaired, if repairable at all, as their more traditional
counterparts. Confirming that a material is repairable
may be important for those used, e.g., where impact
or significant wear or abrasion is likely.
Finally, it is critical that the substitute materials be
documented as part of the historical record of the
building so that proper care and maintenance of all of
the building materials continue, ensuring the contin-
ued life of the historic building.
Choosing an Appropriate
Substitute Material
Once all reasonable options for repair and replacement
in kind have been considered and sufficient justification
for substitute materials has been established, the choice
among the variety of substitute materials currently
available must be made. Rapidly developing technologies
allow a wide variety of materials to choose from that are
intended to mimic historic materials. Many of the materials
that were historically used as substitutes for more
traditional historic materials have themselves become
historic, and some of these early substitutes continue to
be reasonable options as substitute materials today. No
substitute material will exactly match the historic material
in all aspects, but many are able to adequately match
the appearance and relevant physical attributes to make
for a potential substitute. If a substitute material is not
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12
an adequate physical and visual match given the specific
conditions of the building and the project, then it should
not be used to replace distinctive, character-defining
materials and features.
Listed below are various building components or
features and the substitute materials which may, in
some circumstances, be considered for use as possible
replacement materials in a historic rehabilitation project
consistent with the Standards for Rehabilitation. This list
includes different substitute material options available
today for these building features and poses questions
that should be asked and considered when choosing
between the original material and various types of
substitute materials. This is followed by a list of some of
the more commonly used, currently available materials
that may have some applications as substitute materials
and the properties of each that affect their suitability
for use as substitutes. This list should not be read as an
endorsement of any of these materials, generally, or their
appropriateness for use as a substitute material, but it
serves as a reminder that the successful use of any building
material requires a careful consideration of its properties
relative to where and how it will be used.
The above chart lists materials that are sometimes used as substitutes for replacement of historic building features. Even within a given
category, all materials may not be equally suitable as a substitute replacement material for the actual historic material or feature. Any
substitute material should be selected based on its specific physical and visual characteristics, conditions, and intended application
consistent with the Secretary of the Interior's Standards for Rehabilitation.
Masonry
Stone, terra
cotta
Architectural
Metals
Cast & wrought
iron, steel,
pressed metal
Siding
Wood, asbestos
Roofing
Wood shingle,
slate, tile
Decking
Tongue-and-
groove &
square-edge
wood
Molding / Trim
Wood
Aluminum ••••
Cast Stone & Precast
Concrete ••
Fiber Reinforced
Concretes •
Glass Fiber Reinforced
Polymers ••
Fiber Cement •••
Mineral / Polymer
Composite ••••
Cellulose Fiber /
Polymer Composite ••••
Non-composite
Polymers •••
Cellular PVC •••Potential Substitute Materials Historic Building Features
Considering Substitute
Materials
Considering the use of a substitute material
should begin with the following questions about
the conditions and location where it will be used:
• Will the significance or visibility of the
historic feature require a very precise match?
• Is the entire feature being replaced or just a
component of it?
• Are pre-existing conditions contributing to
the failure of the existing material, and, if so,
how will they be addressed/corrected?
• Is the need for replacement due to inherent
deficiencies of the original material?
• Will the material need to resist any
environmental hazards such as flooding
or fire?
Historic Features and Substitute Materials
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13
Historic Building Features: Criteria for selecting an
appropriate replacement material
Masonry
FEATURES: corbels, brackets, balusters, cornices,
window and door surrounds, friezes, wall surfaces,
horizontal surfaces, incidental ornament, columns
HISTORIC MATERIALS: terra cotta, cast stone,
stone, concrete
POTENTIAL SUBSTITUTES: cast stone, pre-cast concrete,
GFRC, GFRP, non-composite polymers (polyurethane),
cast or stamped metal
Questions to ask about the replacement material:
• Can it serve a structural function?
• How is the material affected by moisture?
• Can the material survive flooding and be
reused?
• Can it reproduce the surface texture of the
original?
• Is its shrinkage in curing low enough to allow it
to be molded from existing stones?
• Can matching color be achieved without a
coating and with UV stability?
• Can an adequate match of the surface (color
and texture) be achieved with a coating?
• Is a coating required?
• If it is not self-supporting, is it lightweight
enough to be supported by an underlying
framework?
• Can multiple original units be replicated with a
single replacement piece?
• Where thermal movement is different from the
original material, how will joints accommodate?
• Is the material combustible?
Architectural Metals
FEATURES: pilasters, door and window surrounds,
cornices, incidental ornament, columns, spandrels,
ceilings, sheathing, roofing
HISTORIC MATERIALS: cast and wrought iron, steel,
bronze, lead, aluminum, and stamped steel (usually
galvanized or terne-coated)
POTENTIAL SUBSTITUTES: GFRP, aluminum,
non-composite polymer (polyurethane), GFRC,
metallic/polymer composite
Questions to ask about the replacement material:
• Will the replacement material serve a structural
or cosmetic role?
• Will it expand and contract with temperature
change enough to require special
accommodation in its installation?
• If part of an assembly of mixed materials, how
will any expansion and contraction of the
dissimilar materials be accommodated?
• Will the replacement material increase
deterioration of the historic or surrounding
elements, for instance due to galvanic corrosion,
moisture entrapment, jacking of original
material, off-gassing creating a corrosive
environment, or poor original design of the
historic material?
• How will the replacement material mimic the
surface color/patination of the original material?
• If a coating is needed, what preparation is
needed, and what is its durability or service life
of the finish?
• What attachment and support systems are
necessary?
• If the original element is structural, but the new
material is not, how can supplemental structure
be introduced to support the new?
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14
Siding
FEATURES: clapboard, tongue-and-groove or shiplap
siding, board and batten, shingles
HISTORIC MATERIALS: wood and asbestos
POTENTIAL SUBSTITUTES: cellular PVC, wood fiber/
polymer composite, fiber cement, mineral/polymer
composite
Questions to ask about the replacement material:
• What are the widths, lengths, profiles, thicknesses,
and textures available?
• What, if any, are the finishing requirements,
and/or is it available factory-finished?
• How well does it hold paint, and can prefinished
surfaces be renewed?
• What tools are needed to cut it, and can it be
machined?
• Does it absorb moisture and, if so, to what effect?
• Can the material survive flooding and be reused?
• Will it expand and contract with temperature
change enough to require special
accommodation in its installation?
• What characteristics can affect its handling
(e.g., weight, flexibility, brittleness)?
• Does it have specific fastening requirements?
• Is it susceptible to insect damage?
• What is its impact resistance?
• Does it have a flame spread rating?
• What is the expected lifespan and/or warranty?
Figure 14. Surface texture is an important aspect in matching the appearance of a historic material, especially when a material is viewed at close
range. As seen in these two images, many of the substitute materials produced for siding and trim have an embossed wood grain, making them
incompatible for replacing historic wood that was typically planed to a smooth surface. Some substitute products are available with a smooth
surface as well. Photos: John Sandor, NPS.
Roofing
HISTORIC MATERIALS: wood shingle, slate shingle,
asbestos shingle, clay tile, concrete tile, metal
POTENTIAL SUBSTITUTES: fiber cement, mineral/poly-
mer composite, wood fiber/polymer composite, pre-cast
concrete, metal
Questions to ask about the replacement material:
• What sizes and shapes are available?
• What are color choices?
• What is the color stability of the new material,
and how will it age/weather?
• What is the impact resistance?
• What is its flame spread rating?
• What are the installation requirements of the
new material?
• Can the feature being replaced be custom-
produced if ready-made ones of the new
material are not an accurate match?
• What is the expected lifespan and/or warranty?
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15
Figure 15. Tongue-and-
groove porch flooring is
manufactured in several
different substitute
materials. Each type has
different properties, though
most are more moisture-
resistant than wood. The
prefinished product shown
can be painted when
worn, but repainting is not
recommended for some
product choices. Photo: Oak
Alley Foundation.
Decking
FEATURES: tongue-and-groove, square-edge flooring
HISTORIC MATERIALS: wood
POTENTIAL SUBSTITUTES: cellular PVC, wood fiber/
polymer composite, mineral/polymer composite, non-
composite polymers (solid PVC)
Questions to ask about the replacement material:
• What are the widths, lengths, and textures
available?
• Is it site painted or prefinished?
• How well does it hold paint, and can prefinished
surfaces we renewed?
• What tools are needed to cut it, and can it be
machined?
• What dimensional span does its strength allow?
• Does it absorb water, and if so, to what effect?
• Can the material survive flooding and be
reused?
• Does it require a drainage plane, or can it be
installed atop a membrane?
• Will it expand and contract with temperature
change enough to require special
accommodation in its installation?
• Is it susceptible to insect damage?
• Is it impact resistant?
• Does it have a flame spread rating?
• What is the expected lifespan and/or warranty?
Molding / Trim
FEATURES: run moldings, flat boards, casings, cornice,
frieze, railings, balustrade, columns
HISTORIC MATERIALS: wood, metal
POTENTIAL SUBSTITUTES: cellular PVC, wood fiber/
polymer composite, mineral/polymer composite, non-
composite polymer (polyurethane), GFRP, sheet metal
Questions to ask about the replacement material:
• What are the widths, lengths, and textures
available?
• What, if any, are the finishing requirements
and/or is it available factory-finished?
• How well does it hold paint, and can prefinished
surfaces be renewed?
• What tools are needed to cut it, and can it
be machined?
• Does it absorb moisture, and if so, to what
effect?
• Can the material survive flooding and be
reused?
• Will it expand and contract with temperature
change enough to require special
accommodation in its installation?
• What characteristics can affect its handling
(e.g., weight, flexibility, brittleness)?
• Does it have specific fastening requirements?
• Is it susceptible to insect damage?
• What is its impact resistance?
• Does it have a flame spread rating?
• What is the expected lifespan and/or warranty?
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16
Potential Substitute Materials: Matching properties
and performance needs
Physical Composition and Properties
After assessing different material options based on the intended application, the appropriateness
of a substitute material should also be considered in context of the material’s physical composition,
associated properties, and necessary visual match.
Aluminum
MATERIAL: Aluminum is a highly corrosion-resistant
alloy that can be cast, wrought, or extruded. Molten alu-
minum is cast into permanent (metal) molds or one-time
sand molds forming cast aluminum. Extruded aluminum
is formed by passing heated aluminum through a die
which produces the desired form. Wrought aluminum
is worked using the heated metal and then bending,
stamping, and otherwise shaping the metal. If not self-
supporting, aluminum elements are generally screwed or
bolted to a structural frame. Aluminum can be welded,
but more often sections, particularly extruded ones, are
mechanically connected.
PROPERTIES:
• Isotropic
• Lightweight
• Thermal movement greater than cast iron or wood
• Corrosion-resistant, but direct contact with other
metals may trigger galvanic corrosion
• Lower structural strength that iron or steel
• Ductile - less brittle than cast iron
• Non-combustible
• Retains high definition through molding process and
produces crisp profiles through extrusion
• Can be given a durable metallic finish through
anodization. Surface etching required for paint
adhesion
• Can be machined into a large variety of shapes/
dimensions
Figure 16. Aluminum is a highly corrosion-resistant metal
that is commonly used as a substitute material for cast iron.
Aluminum can be a more affordable and lightweight alternative
to cast iron that retains a similar texture, shape, and
maintenance cycle. Photo: NPS.
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17
Figure 17. The balustrade con-
sists of multiple prior campaigns
of using cast stone to replace
the natural stone. The effective
match for the surface texture
and color of the original stone
allowed individual elements
to be incrementally replaced
only when they had failed, thus
retaining the maximum amount
of original material as long as
possible. Photo: EverGreene
Architectural Arts.
MATERIAL : A cement lime and aggregate mixture that
is dry-tamped into a mold is generally referred to as
cast stone. Cast stone is one of the original substitute
materials. Its longevity has proved that the material ages
compatibly with stone. A wet mix of cement and aggre-
gate poured into molds also has a long history of being
used to produce concrete masonry units mimicking stone
and roofing tiles mimicking clay tile. Both methods have
minimal shrinkage during curing, though they employ
different curing and finishing techniques. Both can
include reinforcing bars and anchorage devices installed
during fabrication. The dry-tamp fabrication method is
especially effective at producing an outer surface with
the appearance of stone.
PROPERTIES:
• Isotropic
• Weight equivalent to stone
• Expansion/contraction similar to stone
• Water absorption may differ from that of any
particular stone
• Can be structural
• Non-combustible
• Vapor-permeable
• May achieve a wide range of color and surface
textures by varying mix, but use of pigments may
reduce UV stability
• Can be coated
• May be tooled to match the appearance of
tooled stone
• Repairs similarly to stone
Cast Stone & Precast Concrete
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18
Fiber Reinforced Concretes (GFRC, CFRC)
MATERIAL : Fiber reinforced concretes are lightweight
concrete compounds modified with additives and rein-
forced with alkaline resistant glass fibers (GFRC), or less
frequently carbon fibers (CFRC). They are generally fab -
ricated as thin-shelled panels and applied to a separate
structural frame or anchorage system. GFRC is typically
sprayed into forms, although it can be poured, and an-
choring devices are included in the fabrication. The color
is derived from the natural aggregates and, if necessary,
a small percentage of added pigments. Because of its
low shrinkage in curing, it can be produced using molds
taken directly from the building.
PROPERTIES:
• Isotropic
• Lighter weight than solid masonry
• Expansion/contraction similar to stone
• No load bearing capacity, so underlying framework
must be used to accommodate any loads
• Material can be fire-rated
• Vapor-permeable
• Can be produced in larger sections efficiently
reproducing repetitive elements or features that
were originally made up of small individual units
• Large range of colors achievable by varying
aggregates, but when pigments are needed UV
stability may be reduced
• May be left uncoated or may be painted
Figure 18. Missing
historic terra cotta
spandrel panels on
all floor levels were
recreated utilizing glass
fiber reinforced concrete
(GFRC) replacements.
New spandrels were
fabricated as individual
components and
attached with metal
clips between historic
terra cotta piers. Photo:
Kris Frail, Dewberry.
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19
Glass Fiber Reinforced Polymers (FRP, Fiberglass)
MATERIAL : Fiberglass is the most well-known of
the FRP products generally produced as a thin, rigid,
laminate shell formed by pouring a polyester or
epoxy resin gelcoat into a mold. When tack-free,
layers of chopped glass or glass fabric are added
along with additional resins. The surface gel coat
can be pigmented or painted. Reinforcing rods and
attachment devices can be added when necessary.
Because of is low shrinkage in curing, it can be
produced using molds taken directly from the building.
Rather than being produced as standard components,
FRP is custom fabricated for individual applications.
PROPERTIES
• Isotropic
• Lighter weight than masonry, similar to sheet metal
• More thermally driven expansion than masonry
or metals
• No load bearing capacity, so underlying framework
must be used to accommodate any loads
• High strength to weight ratio
• Flammable
• Not vapor-permeable
• Can be produced in larger sections efficiently
reproducing repetitive elements or features that
were originally made up of small individual units
• May be difficult to match false joints in multi-
unit assemblies to actual joints that need to
accommodate movement
• Color can be incorporated into the surface gel-coat,
or the surface may be coated
Figure 19. A new, lightweight fiber reinforced polymer is attached to a new metal armature to replicate damaged and missing
elements of a terra cotta cornice. Photo: Quinn Evans.
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20
Fiber Cement
Figure 20. Cement board was used to replace a non-historic infill and mimics the configuration of a typical vehicular door of the period.
Photos: Historic Augusta.
MATERIAL : Fiber cement products are made from
fiber, sand that is ground to a powder, cement, and
proprietary additives to reduce moisture absorption.
The fiber used in roof products is glass fiber alone,
whereas siding and trim board products are primarily
wood fiber. The material is formed with a smooth or
textured surface, cut to standard sizes of panels, boards,
or shingles, and cured in an autoclave. Roofing material
has integral color, but board and siding products are
produced with a primer, if not fully factory finished.
Most siding and trim boards are embossed with a wood
grain on one surface and are smooth on the other, the
smooth side being the appropriate surface to imitate
planed wood.
PROPERTIES:
• Products are minimally orthotropic
• Heavier and more brittle than wood, limiting
available lengths
• Very little thermal- and no moisture-driven
movement
• Low water absorption, but not recommended for
ground or roof contact
• Class A flame spread
• Resists insect damage
• Available in limited thicknesses and widths
• Not machinable, but may be cut with special carbide
blades; cutting requires dust collection and personal
protective equipment
• Cut edges require sealing
• Available unfinished, primed, or prefinished, and
must be painted (with latex paint)
• 15-year limited warranty typical
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21
Mineral / Polymer Composite
MATERIAL : Calcium carbonate or fly ash are mineral
ingredients held in a matrix of various polymers to
produce materials formed or molded into a number of
building products. Additives found in some of the roof-
ing products include pigments and UV stabilizers. Some
use a substantial portion of recycled material. Different
combinations yield products with different properties,
each formulated for a specific building component.
When the material is fly ash with some glass fibers
bound in a matrix of polyurethane, it is identified as
polyash. Siding, trim, bead board, and deck products
are primed or prefinished, whereas roof products have
integral color.
PROPERTIES:
Fly ash (siding and trim)
• Isotropic
• Heavier and more brittle than wood, and lacking
structural capacity
• Little thermal or moisture-driven movement
• Sufficiently low water absorption to permit ground
contact
• Class C flame spread
• Resists insect damage
• Available in limited thicknesses and widths
• Machinable with carbide tools blades; requires dust
collection
• Cut edges do not require sealing
• Must be painted
• 30-year limited warranty typical
Calcium carbonate or recycled rubber (roofing)
• Isotropic
• More thermally-driven movement than slate
or wood
• Little to no moisture absorption
• As shingles: lighter and more flexible than slate
• As tongue-and-groove decking: heavier and
harder than wood
• Not vulnerable to insect damage
• Available in limited dimensions
• As shingles: Class 4 impact resistance, and flame
spread ratings ranging from Class A to Class C
depending on the specific product
• As shingles: integral color, that may be subject
to fading
• As tongue-and-groove decking: prefinished
with non-renewable finish, and can be cut with
woodworking tools
• 50-year limited warranties on roofing products
typical
Figure 21. A mineral
polymer composite
siding was available in
the profile very similar
to the historic siding.
The replacement siding
was used where the
original material was
almost completely
missing beneath
a more modern
covering. Areas where
the original wood
was largely intact
were replaced with
matching wood to
sustain more of the
material integrity of
the building. Photo:
Belk Architecture.
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22
Cellulose Fiber / Polymer Composite
MATERIAL : Wood strands or fibers are coated with
resin for moisture resistance and zinc-borate for insect
and fungal-decay resistance, then consolidated under
heated pressure. Solid composite core boards are cut
from sheets of material, then factory-primed or finished.
Resulting siding and trim board products can be referred
to as engineered wood, fiber board, or hardboard.
Products may be embossed with a wood grain or have
a smooth finish, the smooth side being the appropriate
surface to imitate planed wood. Siding, trim, and
tongue-and-grove decking with a slightly different
properties are produced by extruding polyvinyl chloride
(PVC) combined with non-wood cellulose. Roofing
shingles are molded from fine wood fibers, color
additives, and UV stabilizers bound with polypropylene
or polyethylene (thermoplastics).
PROPERTIES:
Predominantly Cellulose (siding, trim and decking)
• Minimal thermal movement
• Resistant to moisture-driven movement
• Lighter and more flexible than solid wood, but lacks
structural capacity
• Rice hull cellulose: can span typical floor-framing
spacing as decking
• Low water absorption (for wood, no ground or roof
contact)
• Class A or Class C flame spread
• Resists insect damage
• Available in limited dimensions
• Machinable with woodworking tools
• Wood cellulose: Cut edges must be sealed and
may need additional surface prep for finish; must
be painted if unfinished or primed, also available
prefinished
• Rice hull cellulose: Accepts stain/paint, but no
finish required
• 30–50 year limited warranty, depending on
manufacturer
Predominantly Polymer (roofing)
• Minimal thermal movement
• Little to no moisture absorption
• Lighter and more flexible than slate
• Class 4 impact-resistance
• Class A flame spread
• Available in limited shingle size
• 50-year limited warranty typical
Figure 22. A porch was reconstructed using posts fabricated on
site from a smooth-surface cellulose/polymer composite material.
Though the face of the posts are painted, the lack of paint on the
bottom at the cut ends is not consistent with manufacturers’
recommendations. This treatment will allow moisture to be
absorbed, shortening the life of the new replacement feature.
Photo: John Sandor, NPS.
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23
Figure 23. 3-D printing using various polymers is occasionally used to replicate missing metal or wood features. This new application is
continually being refined, but the application can be successful when a painted, lightweight feature needs to be replicated. Photo: NPS.
Non-composite Polymers
MATERIALS: The main two polymer materials used
without significant other components are polyurethane
and polyvinyl chloride (PVC). Polyurethane millwork is
constructed of urethane foam created by mixing isocya-
nate and resin. The polyurethane mixture is kept under
pressure in a mold as it expands to any desired shape.
These molded products have a closed-cell, foamed core
with a denser surface skin. Polyurethane products can
have exterior applications but are more often used
for interior features. Polyvinyl chloride (PVC) in a solid
extruded form is another polymer that can have archi-
tectural application as tongue-and-groove decking. Vari-
ous polymers formed using 3-D printing are also being
explored as replacements for painted metal or wood
ornamental features.
PROPERTIES: Each of the two groupings has distinct
physical properties
Urethane Foam (moldings and decorative elements)
• Lightweight and flexible, but lacking structural
capacity
• More thermally-driven movement than wood or
stone, but less than cellular PVC
• Does not absorb water
• Flammable
• Resists insect damage
• Can be cut with standard woodworking tools
• Adhesive and mechanical fasteners both
recommended for installation
• Supplied primed and must be painted (latex paint)
• Lifetime limited warranty typical
Solid PVC (flooring)
• Isotropic
• Heavier and less flexible that wood
• Minimal thermal movement
• Does not absorb water
• Strength to span typical floor-framing spacing
• Impact-resistance greater than wood
• Class A flame spread
• No insect susceptibility
• Good paint adhesion, but also available prefinished
• 20-year warranty typical
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24
Cellular Polyvinyl Chloride (PVC)
MATERIAL : Varying amounts of calcium carbonate
and a foaming agent are added to melted PVC before
passing through an injection die and then a calibrator
to produce the shape and size of the finished product.
Cellular PVC is produced as sheets, boards, and mold-
ings. Differences in the specifics of the equipment and
the rate of cooling create two varieties of product, with
distinct properties. One is known as free-foam, having a
fairly consistent structure throughout its section, and the
other is identified as Celuka, having a skin that is denser
than its core. This primarily affects the ease with which
the product can be milled and shaped. The material is
white and needs no applied finish. When produced for
decking the material has a colored and textured wear
layer over the PVC core.
PROPERTIES
• Isotropic
• Lighter and more flexible than wood
• Less strong than wood (in tension and shear), but can
span typical floor- framing spacing as decking
• More impact-resistance than wood
• Negligible water absorption; no moisture-driven
movement, unlike wood
• Subject to thermal expansion and contraction
significantly greater than wood, though the thermal
movement is less for the same dimension than the
cross-grain moisture-driven movement of wood
• For longer pieces, thermal movement requires
manufacturer’s specifications to be followed for
attachment, and inclusion of expansion joints when
installed at low temperature (joints should be glued)
• Class A flame spread
• Resists insect damage
• Machinable with woodworking tools, though cut
edges may need additional surface prep for finish
• Good paint adhesion; if painted, high light
reflectance (HLV) is recommended to minimize heat
driven expansion
• 25–30-year limited warranty, depending on
manufacturer
Figure 24. Cellular PVC when painted can be used to replace
deteriorated wood features. This beadboard set in a wood frame
was not historically designed to shed water effectively and had
deteriorated. Cellular PVC was able to match the appearance of the
wood details, while its properties were well matched to the shady
location, painted finish, and limited size and configuration within
the overall assembly; thus, it should provide a long-lasting solution
for this application. Photo: Jennifer Balson Alvarez, NPS.
Acknowledgements
John Sandor, Architectural Historian, David Trayte, Historical Architect, and Amy Elizabeth Uebel, Architectural Historian,
Technical Preservation Services, National Park Service, revised Preservation Brief 16: The Use of Substitute Materials on Historic
Building Exteriors, originally written by Sharon C. Park, FAIA, FAPT, and published in 1988. The revised Brief contains expanded
and updated information as well as new color photographs describing the general issues and application of substitute
materials on historic buildings.
The authors wish to thank the following: Peyton Hall, FAIA, Principal Architect Emeritus, Historic Resources Group, Mary
Jablonski, President, Jablonski Building Conservation, Inc., Thomas Jester, FAIA, FAPT, LEED AP, Principal, Quinn Evans, Sharon
Park, FAIA, FAPT, Associate Director Emerita, Smithsonian Institution, Debra Slaton, Principal, Wiss, Janney, Elstner Associates,
Inc., for their guidance and review of this revision; and to Brian Goeken, Chief of Technical Preservation Services, National Park
Service, and Jo Ellen Hensley, Elizabeth Tune, and Jennifer Oeschger, Technical Preservation Services, National Park Service,
for their help in the editing of the publication. Illustrations not specifically credited are from National Park Service files. Front
cover image: Installation of a new roof feature on a ca.1895 commercial building. The dome was constructed of fiber-reinforced
polymer to replicate the missing original feature in Aurora, Illinois, 2023. Photo: Kelsey Cozens/JH Real Estate Partners LLC.
This publication has been prepared pursuant to the National Historic Preservation Act of 1966, as amended, which directs
the Secretary of the Interior to develop and make available information concerning historic properties. This publication is
available from the Technical Preservation Services website at http://www.nps.gov/tps/ or hard copies may be purchased from
the Government Printing Offices at the U.S. Government Bookstore at https://bookstore.gpo.gov/. Comments about this
publication should be addressed to Technical Preservation Services, National Park Service, 1849 C Street, NW, Mail Stop 7243,
Washington, DC 20240, or by email to NPS_TPS@nps.gov.
This publication is not copyrighted and can be reproduced without penalty. Normal procedures for credit to the authors and
the National Park Service are appreciated. The credited photographs used in this publication may not be used to illustrate
other publications without permission of the owners.
September 2023
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