Phillips, Morgan W. and Dr. Judith E. Selwyn.Epoxies for Wood
Repairs in Historic Buildings. Washington, DC: Office of Archeology
and Historic Preservation, Heritage Conservation and Recreation
ServiceU.S. Department of the Interior, 1978
This publication deals with two main subjects; 1) the chemical
compositions and uses for epoxies in wood consolidants and
patching; and 2) case studies involving the restoration of
the Longfellow house. Although published in 1978, much of
the information contained in it is relevant today. Much of
what is discussed is highly technical. In addition, more recent
information merely expounds on this information.
Kahn, Eve M. "Wood Restoration: Epoxies Fill in the G
* A * P * S," Clem Labine’s Traditional Building,
Sept – Oct 1991, v. 4, no. 5: pg. 16-23.
Of all the topics in restoration the one that is most misunderstood
deals with epoxy work. In selecting epoxy to work with, one
must follow certain guidelines:
- Epoxy is the right job when one wants to keep: *the historical
material and minimizing disruption to intact elements are
important; * the parts in need of restoration would be difficult
to replace; * nearly invisible repairs are desired; and
* skilled craftspeople are available (Kahn, p. 16)
- Choose an epoxy suited to the project.
- Be wary of inexpensive formulas.
- Make sure the epoxy’s cure time fits your needs.
- Epoxies that mix 1:1 are easiest to handle in the field.
- Don’t forget the effect of climate on epoxy. Heat
speeds cure time, so mix small batches when working in strong
- Don’t slather sound wood with epoxy in an effort
to protect it. Wood under consolidated areas can rot because
of trapped moisture.
- Be aware of the controversy surrounding the use of solvents
in epoxy. There are many products now available without
- Use pigments only as the manufacturers recommend.
Marshall, James R. "A Specifier's Guide to Epoxies for
Restoration & Repair," Clem Labine’s Traditional
Building, Jan-Feb 1998, v. 11, no. 1: pg. 20, 22, 24
This article by James R. Marshall discusses the uses of epoxies
for restoration and repair. Developed late in World War II,
epoxies first were developed as super strong adhesives. They
have evolved into one of the most versatile materials now
available for all manners of restoration and repair (Marshall,
p. 20). Not only are epoxies today used as adhesives, but
for structural component restoration as well. Wood restoration
problems include rotted, dried out or spongy wood. For wood
restoration, the process is normally a two step process involving
a consolidant (the primer) and a hardener.
There are varying beliefs involving the success or failure
of the consolidation approach. Mr. John Stahl, the technical
director of Advanced Repair Technology, believes that the
pre-consolidation approach will lead to eventual failure.
His belief is in a system that involves a primatrate (a two-part
low viscosity epoxy and an elastomeric wood repair compound).
By using paint brushes to apply the primatrate, it penetrates
the wood fibers, which is essential in making the wood stronger.
Mr. Stahl also maintains that all decayed wood be removed
prior to beginning the restoration process. By not removing
the decayed wood, problems such as expansion/contraction in
the decayed wood compromises the bond, inadequate “peel
strength” in the epoxies, and inadequate flexural strength
in the epoxies all can lead to failure. (Marshall, p. 20)
Mr. Marshall also expounds the virtue of epoxies in the restoration
of structural components, such as support timbers. Epoxies
work well in compressive situations because epoxy compounds
can be stronger than concrete in compression. As for tension,
the answer is also yes. However, when using epoxy in elements
in tension, such as a beam, it is essential that a structural
engineer signs off on the work. The lack of proper engineering
for a structural repair can result in tremendous failure.
For example, if a wooden beam’s end is decayed in a
masonry pocket, the epoxy used in the repair must be treated
like concrete and aggregate added to it. In addition, the
restored section must be firmly tied into the sound portion
of the beam by the use of fiberglass (not metal) rods. Fiberglass
rods work better than metal rods for two reasons: 1) fiberglass
and epoxies have similar expansion/contraction characteristics;
and 2) residual oils on metal could disturb the epoxy bond.
Lief, Judith Siegel. "The Wide World of Epoxies,"
Clem Labine’s Traditional Building, Sept –
Oct 1995, v. 8, no. 5: pg. 34, 36
According to Judith Siegel Lief, the domains of epoxy liquids
run the gamut between adhesives (known as the Cadillac of
glues because they are virtually shrink free and bond to almost
all materials) to wood consolidants and fillers (including
bonding agents, marine resins, crack injection compounds,
concrete restoration products and structural adhesives).
Prior to using epoxies, one needs to know what the problem
is and what is available to fix it. Epoxies are classified
into three main categories:
- Wood Consolidents: The use of low viscosity epoxy that
is clear in appearance and which stabilizes and strengthens
the remaining wood. Three primary factors affect the rate
of curing: a) temperature of the epoxy; b) amount of material
being treated; and c) environmental temperature.
- Cosmetic/Non-Structural Repair
- Structural Repairs: Epoxies can be formulated with good
flow characteristics so, mixed with aggregates, they can
be used like concrete. Included would be fiberglass rods
(65% glass + 35% polyester fill) which would make the repair
load bearing and structurally reliable.
Leeke, John. "How to Use Epoxies to Repair Rotted Exterior
Wood," Old House Journal, May – June 1989, v. 17,
no. 3; pg. 22 - 24
John Leeke concentrates primarily on the repair and restoration
of non- structural wood. Some of the advantages in using epoxies
include ease of learning to use epoxy; epoxy materials hold
up well to weather; it may not be necessary to remove affected
parts from the building; and epoxy repair saves as much of
the original material as possible. Epoxy should only be considered
where long life is the goal of the project. Mr. Leeke recommends
keeping a epoxy kit on hand for quick repair work. Within
this kit should be:
- two 10 fluid oz. cans with snap on lids; each labeled
with parts A and B of the adhesive paste filler
- two 8 fluid oz bottles, each labeled with parts A and
B of the consolidant
- a few empty bottles for mixing and application
- rags of various sizes
- gloves; several disposable and one heavy pair
- oil clay
- putty knives
- mixing boards
- epoxy materials
- 2 dozen application bottles
- mixing sticks
- bottle cleaning tools
- channel lock pliers
- allen wrenches
- needlenose pliers
Use clean mixing materials and tools to avoid contamination
and maximum penetration is required for an effective bond.
Practice safety when using epoxies:
- epoxies are toxic chemicals
- avoid contact with eyes and skin
- avoid breathing fumes
- watch for spills and drips
- use soap and/or detergents not solvents to wash off of
- use disposable stir sticks and gloves
- epoxies are flammable