EPDM: Restore or Re-roof?

May 15, 2004

EPDM single-ply roof systems have represented a third of the
volume of the low-sloped commercial market for close to twenty
years. The majority of these roofs were installed to receive the manufacturer’s
10- or 15-year warranty, so many are either beyond the
duration of the warranty or soon will be.
EPDM has achieved a reputation in the industry as a longlasting
material, and advancements in materials, techniques, and
components have given manufacturers the confidence to offer the
industry’s longest warranties of thirty years.1
Many building owners and designers are considering restoring
these existing EPDM systems in lieu of re-roofing (tear-off or retrofit).
Restoration costs are typically 10% to 30% of the re-roofing cost,
depending on the roof condition and the system attachment method.
There are many factors to consider when deciding between
restoration and re-roofing such as cost, time, viability, codes, and
environmental impact.2 This paper discusses only certain restoration
procedures, and these procedures should be considered in
conjunction with the above factors. The information will also help
in designing new or retrofit EPDM systems with provisions for
longer service life and initial installations that will be easier to
restore in the future.
Many manufacturers have prepared specifications for repair or
restoration of their existing systems and may even offer an extension
of the warranty coverage if the owner elects to restore in compliance
with specifications. These proprietary specifications are comprehensive
because manufacturers are conservative when assuming this
additional warranty liability, and
these types of restorations generally
cost more.
Roof consultants who wish to
control costs while optimizing the
restoration may prepare restoration
specifications specific to each
EPDM system, based on existing
conditions that may be driven by
site-specific circumstances and
the owner’s individual needs.
These specifications are usually
descriptive since there are no reference
standards for restorations,
and it would be difficult to specify
and measure performance of the
restoration work. It is also important
to specify products that are
compatible with one another. It
may be possible to specify a different
manufacturer’s EPDM products
to restore an existing EPDM
roof, but it is not recommended to
use combinations of products from
different manufacturers for the
restoration. Most manufacturers
Photo 1: Bridging on an EPDM ballasted system. offer similar products for their
26 • Interface September 2004
EPDM systems, but there are
enough differences that the specifier
will need to become familiar
with the products of the manufacturer
that is specified.
There are several important
ideas to keep in mind when renovating
EPDM. The first is that the
primary reason for renovating the
existing system is to extend the
service life of an existing EPDM
membrane that is still in good condition.
Always try to preserve the
integrity of the membrane sheet,
or better put – don’t cut it. There
are some exceptions when it may
be necessary to cut the sheet, but
most restoration procedures keep
the sheet intact.
Also, don’t make coating the
roof the number one priority.
There are a number of benefits to
applying a coating over the existing
membrane or on the exposed
wall flashing, but in most cases,
the concern should be to bring the
system back to a condition that
provides additional service life. An
existing installation may be exhibiting varied levels of distress. The
coating should be the final step, applied after the other topical,
membrane-specific restoration work is completed. Remember that
repairs to a coated EPDM roof are much more difficult to execute
than on a previously uncoated membrane and, therefore, are more
expensive. Repairs to an uncoated EPDM surface are typically
superior to those on a coated or partially coated surface.
There are three configuratons to affix to the EPDM membrane:
fully adhered, ballasted, and mechanically attached. Each is very
different in regard to its overall restoration and the requirements
for detailing. All three systems may be renovated, but the majority
of restorations to date have been on fully adhered or ballasted systems.
Restorations to mechanically attached systems involve additional
requirements because of dynamic stresses on the seams and
fastening components.
To receive the maximum benefit, restoration activity should be
focused where problems are most likely to show up on the existing
system. Historically, the two areas that have contributed to problems
on EPDM systems are the seams and base tie-in attachments
at transitions from the plane established by the roof and adjacent
interfaces with walls, etc. As such, these two areas should be the
primary focus of any EPDM restoration.3
Seam technology for EPDM systems has improved, and it is
important to identify the seaming techniques that were used on the
initial installation as well as to identify the cause of seams showing
signs of failure. The basic repair is to overlay seams with a tape
adhesive-backed, uncured flashing. This is commonly referred to as
“stripping in” the seams. Procedures and products to strip in seams
vary, depending on the membrane manufacturer, system type, and
existing conditions. The cost also varies, depending on the procedure
utilized. With more substantial methods implemented, the
cost could be double that of a routine method.
The first step in stripping in the seam involves cleaning the
existing membrane. Many seams fail prematurely due to a failure to
properly clean the splice area when the membrane is new, so proper
cleaning of the in-service membrane is a top priority. The membrane
should be cleaned with detergent and thoroughly rinsed with
clean water at least 12 inches in each direction from the seam edge.
On ballasted systems, pull the pavers or stone away to expose the
membrane and to prevent additional dirt from entering the repair
area. Sweeping away all loose dirt simplifies the cleaning process,
and many contractors prefer to aggressively clean with a dry, stiff
bristle brush or broom prior to applying detergent and water.
Some manufacturers offer cleaning solutions specific to aged
membrane, while others offer solutions to clean the EPDM prior to
the application of their respective roof coatings. These solutions are
now recommended for cleaning EPDM membrane prior to repairs.
The cleaners are easy to use, and provide excellent results, especially
when rinsed with a powerwasher (2000 psi). Exercise care not
to aim the power washer nozzle at the lap edge, thereby possibly
opening the lap.
An additional cleaning of the dry membrane with the manufacturer’s
solvent membrane cleaner and re-adhering any loose seam
areas with splice adhesive are both recommended prior to the application
of the splice adhesive or seam primer for the overlay.
The next step is application of the primer or adhesive used with
the tape adhesive-backed flashing. It is generally best to use the
primer recommended by the flashing manufacturer; however, there
may be some instances in which using the standard splice adhesive
prior to application of the tape adhesive backed flashing should be
considered. The splice adhesive could be used instead of primer or
as an additional application. The thicker application and higher
September 2004 Interface • 27
Photo 2: Old base tie-in detail with polymeric batten strip.
28 • Interface September 2004
solids content of the splice adhesive offer better protection against
small leaks occurring over irregular surfaces, but this additional
application usually involves a higher cost.
The products to strip in the seams will vary, and many manufacturers
will offer several. To determine the optimal product,
decide whether strength and durability or a tightly bonded seam is
the priority. Thinner, less cured flashing products give a tighter
bond and conform better to surface irregularities, while the thicker
flashing products that are more cured offer more strength and
durability. If the seam is still bonded but there are leaks occurring
at the factory seams or other irregularities, then the products with
less cure would be a better choice. The less cured products are generally
preferred to strip-in seams on newer installations. If the
existing seams are open or there is tension on the membrane, then
the thicker cured products would be a better choice. It’s also a good
idea to use the less cured products in conjunction with the cured
products at all seam intersections. Most manufacturers require
this, and some have developed specialized uncured patches for “T”-
lap intersections.
Application of lap sealant or caulking to all exposed seam edges
is also a good idea. Many manufacturers do not require this lap
sealant on the edge of the flashing material on new EPDM installations,
but do recommend or require lap-sealed edges on repairs to
existing membranes. Procedures to apply the lap sealant also vary
among manufacturers.
Mechanically fastened systems will usually require additional
enhancements to prevent the underside or back edge of the seam
from pulling apart. The fasteners in the seam and decking must
also be evaluated for long-term performance. The evaluation of
these seams is beyond the scope of this article.
Base tie-ins are the second major area to address on EPDM
restorations. The base tie-ins are one of the three components of a
wall or curb flashing. The other
two components are the wall flashing
and the final termination
detail. If there are concerns with
more than one of these components,
then it may be more cost
effective to remove all of the existing
materials and install new
flashing according to the manufacturer’s
specifications for new
construction or re-roofing.
Base tie-in or membrane
securement details are required
on single-ply systems to keep the
membrane tight in the angle
change and to prevent the membrane
from pulling away, resulting
in a tented or bridged condition
(See Photos 1 and 2). The cause of
the force pulling on EPDM roofs is
a subject of much debate. Some
believe that cause is membrane
shrinkage, while others believe
that the cause is the thermal
expansion and contraction of the
membrane. Some believe that it is
a combination of both of these
forces. Many do believe that
regardless of the cause of the forces on the EPDM, a properly constructed
base tie-in detail will resist these forces and prevent the
tented or bridged condition.4
The manufacturers’ details have evolved over the years, and
most now recommend similar details intended to accommodate
ample resistance to the forces on the field membrane. The details
utilize a strip of reinforced EPDM membrane that is usually six
inches wide, anchored to the deck or wall, and adhered to the bottom
side of the field membrane. The field membrane continues up
the wall and serves as the flashing. These securement strips are
attached with the manufacturer’s specified fasteners through stress
plates or batten strips at a rate no greater than 12 inches apart.
The stronger details incorporate a reinforced EPDM securement
strip that has pressure-sensitive seam tape pre-applied to mate to
the bottom side of the field membrane and resist forces ranging
from 300 to 400 pounds per lineal foot. This is the base tie-in detail
required by most manufacturers for 30-year warranties, and it is
also the detail preferred by most contractors, regardless of the warranty
length.
These securement strips with pressure-sensitive seam tape
enhance the performance of marginal conditions at base tie-in
details; however, installation requires cutting open the membrane
to attach the strip. Cutting the membrane is often mandatory to
relieve the tension if there is a failed base tie-in detail with a tented
or bridged condition.
The common procedure is to clean the areas of the existing
membrane 18″ from the angle change onto the deck and 18″ from
the angle change up the wall. After the membrane is clean and dry,
cut the membrane along the old row of fasteners. Allow the membrane
to rest flat on the deck surface and against the wall. Snap a
chalk line 5″ from the angle change out onto the deck and up the
Photo 3: Base tie-in repair with securement strip and new EPDM membrane.
September 2004 Interface • 29
wall and cut along these lines. Remove existing fasteners, batten
bars, and other material from the existing base tie-in detail. Install
the fasteners in the new securement strip, utilizing a pattern and
frequency consistent with that specified by the manufacturer.
Requirements for fasteners, stress plates, batten bars, and position
of the strip do vary between the manufacturers, so it is good practice
to follow the particular manufacturer’s recommendations.
Re-adhere the backside of the existing flashing membrane and
cover the open area with a minimum 18″-wide piece of seamless 60-
mil membrane. Any loose existing deck membrane is re-adhered on
fully adhered systems. See Photos 3 and 4. Many manufacturers
offer this material precut for this purpose, and some produce the
material with pressure-sensitive seam tape applied to one or both
edges. Use the recommended primer to adhere the new membrane
to the pressure-sensitive seam tape on the securement strip.
Adhere the new membrane to the wall, and on fully-adhered systems,
adhere it to the deck or insulation substrate. Seam the edges
onto the clean existing flashing using the procedures mentioned
earlier.
Existing base tie-in details that did not incorporate the securement
strip or those that exhibit the tented or bridged condition
should be addressed with the above procedure. Many EPDM roof
systems installed since the late 1980s have base tie-in details with
a securement strip that are functioning well and do not show signs
of tenting or bridging. Depending on system type and how the base
tie-in detail was constructed, the existing detail may not need to be
rebuilt or may only require an enhancement.
One key factor is if the EPDM strip used in the detail has a pressure-
sensitive seam tape pre-applied or if the strip was glued to the
field membrane with seam adhesive. The detail where the strip was
adhered to membrane with only seam adhesive should be enhanced
or rebuilt because this seam strength is less than with seam tape.
Another factor is the type of system. The base tie-in detail is most
critical on the mechanically-fastened system, and least important
for the fully-adhered system. The best combination is a fullyadhered
system with a securement strip with pressure sensitive
seam tape pre-applied for the base tie-in. This combination is typically
the minimum requirement for the manufacturer’s 30-year
warranty. Therefore, many existing base tie-in conditions should be
rebuilt or enhanced to properly function for the expected life of the
restoration.
One possible enhancement is to clean the membrane surface,
add new fasteners and stress plates centered between the existing
plates, and cover with a 6″ to 9″ uncured flashing material with
pressure-sensitive seam tape pre-applied. If there is any doubt
about the adhesion of the existing strip, proper fastener type, or
fastener pull-out resistance, then the conservative approach would
be to rebuild the detail.
Roof edge details were not identified as a major cause of EPDM
problems; however, they must be addressed when restoring the system.
There are three basic styles of edge details:
• Flanged drip edge or gravel stop metal stripped in with
uncured EPDM flashing.
• Snap-on metal edges.
• Compression metal details (aluminum termination or drain
bars in the gutter and extruded angle metal).
All roof edge details provide a watertight seal and securement at
the edge of the membrane. These details also provide the first line
of defense of wind uplift protection for the system. Performance of
30 • Interface September 2004
these details is dependent on the condition of the metal, wood
blocking, and fasteners. Until recently, there was no standard for
roof edge performance. Many existing edge details would fall short
of the minimum standards if all of the components were new, and
are likely substandard, particularly with worn-out components.
Replacement of the entire edge detail and the related components
should be considered.
Penetration flashings must also be addressed. Another rule is
that the best penetration flashing is no flashing at all. If a particular
projection is no longer required, remove the projection and
flashing, fill in the void, and install a cured EPDM patch over the
area. Re-flash all other existing penetrations. Use non-penetrating
supports for pipes and equipment whenever possible.
Roof drains are particularly important because of the amount of
water that flows over these details. Drain details are also vulnerable
to cuts and punctures due to the stress on the membrane at the
drain fixture. The stress on the membrane increases as slope of the
drain sump increases. Most manufacturers limit slope in the sump
area to between 4:12 and 6:12 for non-reinforced membrane and
between 1:12 and 2:12 for reinforced systems. If the existing sump
exceeds these slope limitations, then the sump area should be
reworked to achieve the proper slope.
Replace the membrane at all drains with a target patch that
extends at least two feet out of the sump area. The target patch
material should be the same thickness or thicker than the existing
membrane and should be cut so that there are no factory seams on
the patch material.
Cut the existing material around the outside of the drain ring
and remove all of the material and sealant from the compression
area of the drain bowl. Install the membrane in the compression
area according to the manufacturer’s drain detail. Specify the use
of a hole punch for the bolt holes through the membrane. Complete
the seam around the target patch
and then strip these seams in following
the procedures outlined
earlier.
Restorations of existing EPDM
systems will continue to gain
acceptance as more people
become aware of the advantages of
this option and as restoration procedures
continue to improve. This
article is limited to the common
details. Sources for additional
information for other details or
unique situations include the
EPDM manufacturers, roofing
contractors that specialize in
repair and maintenance of EPDM
roofing systems, and the EPDM
Roofing Association. ■
REFERENCES
1Trial, T., Robertson, R., Gish, B.
D., “EPDM Roof Membranes:
Long-term Performance Revisited,”
Proceedings of the 18th
International Convention and
Trade Show, RCI, pp. 101,
2004.
2Hutchinson, T. W., “EPDM Roof Restoration,” Proceedings of the
CIB World Building Congress 2004.
3Cullen, W. C., Project Pinpoint Analysis: Ten-Year Performance
Experience of Commercial Roofing 1983 – 1992, 1993.
4Paroli, R. M., Delgado, A. H., Dutt, O., Smith, T. L., and
Simmons, T., “Shrinkage of EPDM Roof Membranes:
Phenomenon, Causes, Prevention, and Remediation,”
Proceedings of the 11th Conference on Roofing Technology,
NIST/NRCA, pp. 90, 1995.
Thomas R. Julian, RRC, RRO, CCCA,
is the training manager for Firestone
Building Products Company, Carmel,
IN. In this position, he is responsible
for Firestone’s contractor training programs
for EPDM, thermoplastic, and
asphalt roofing systems. Tom has 19
years of experience in the roofing
industry and is past president of the
Ohio Valley Chapter of RCI. He has
presented at the RCI convention and
region meetings and taught RCI classes.
He serves on the MRCA Certified
Roofing Torch Applicator (CERTA) Committee and is a MRCA
CERTA Instructor-Trainer and an authorized OSHA outreach
instructor.
ABOUT THE AUTHOR
THOMAS R. JULIAN,
RRC, RRO, CCCR
Photo 4: Completed EPDM base tie-in restoration.