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EPDM or membrane roof (C) Daniel Friedman Membrane & EPDM Rubber Roofing
Life, Types, Sources, Installation, Defects, Repairs

  • EPDM, RUBBER, PVC ROOFING - CONTENTS: Rubber roof roof installation, inspection, troubleshooting, repair, life expectancy. Membrane roof materials - Rubber Roofing properties of EPDM roofing. Definition of Membrane roofing. Types of Membrane roofs: EPDM, Rubber Roofs, PVC Roofs, Others. EPDM roofs, Rubber Roofs, & PVC Roof properties
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EPDM Roofs, Rubber Roofs & PVC Roof coverings:

this article describes membrane roofing materials, flat roof membrane choices, flat roof installations, inspection, EPDM or rubber roof defects, flat roof leak detection, flat roofing repairs, and flat roof membrane product sources.



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Membrane Roofing Materials:

EPDM roof (C) Daniel FriedmanEPDM, PVC, or Rubber Roof Choices, Costs, Life Expectancy, Flat Roof or Membrane Roof Characteristics

"Membrane roofs" is a general term that may be applied to a low slope or flat roof covered by any means that is intended to produce a continuous waterproof barrier.

Our photo (left) shows roof penetrations and flashing on an EPDM roof in New York.

[That chimney may be too short, violating code and safety if it extends less than 2 feet above the roof surface.]

Look closely and you can see the marks left by round anchors that tied rooftop insulation to the roof deck below. This telegraphing of insulation fasteners is not a roof defect - it's normal.

Asphalt shingles, in contrast to the EPDM roof shown here, , are not a "waterproof membrane" and depend on the drainage offered by the roof slope to function effectively.

That's why without special measures (discussed at LOW SLOPE ROOFING) we don't expect to find shingles installed on roofs of pitch lower than 4" of rise in 12" of run.

Because we discuss other popular membrane type roofing systems separately at ROLL ROOFING, ASPHALT and MODIFIED BITUMEN ROOFING, here we focus on EPDM roofs or "rubber roofs".

Carson Dunlop's illustrations (below) compare an EPDM roof membrane installation and a PVC roof membrane installation.

EPDM Roofing Installation, Properties, Life

EPDM rubber roof installation and repair details (C) Daniel Friedman Eric galow

Definition of EPDM - "Rubber Roofing"

EPDM is an acronym for Ethylene Propylene Diene Monomer, a rubber-like sheet or membrane, usually black, and usually not reinforced with other materials.

EPDM roofs are usually glued down - the "fully-adhered" application method. Overlapping seams are glued and flashings are glued to the EPDM surfaces as well.

EPDM Roof Life Expectancy

The average life expectancy of an EPDM roof, according to industry sources, is 22 to 35 years, while often manufacturers warrant the EPDM material for as much as 40 years.

Separately at EPDM ROOF COATING REPAIRS we include research on EPDM life and the use of coatings to extend its life.

In a companion article EPDM ROOF LEAK REPAIRS we discuss tracking down and fixing leaks in rubber roofs.

As discussed in Best Practices Guide to Residential Construction, chapter on BEST ROOFING PRACTICES:

While a variety of single-ply roofing membranes are used on commercial jobs, only EPDM has become widely used on residential sites. EPDM, a form of synthetic rubber, owes its popularity to its relative ease of installation combined with exceptional durability. If installed correctly, roofs often exceed 20 years of service and callbacks are exceedingly rare.

While some commercial EPDM systems are loose-laid or ballasted, residential applications are typically fully adhered. Rolls typically vary from 10 to 50 feet in width and from 50 to 200 feet in length, but many distributors will cut a piece to size for smaller jobs.

If possible, use a single piece with no seams for the field of the roof. EPDM membranes are available in two thicknesses: .045 inch and .060 inch.

For fully adhered applications or any application where foot traffic or decking is planned, the thicker membrane is recommended.

If you didn't already know, and in case it's on your roofing quiz, "EPDM" is the abbreviated name of a synthetic rubber termed Ethylene Propylene Diene Monomer.

Substrates for EPDM Roofs

EPDM rubber roof installation and repair details (C) Daniel Friedman Eric galow

EPDM can be bonded to a wide variety of substrates, including plywood, OSB, fiberboard, and urethane insulation board.

The substrate should be smooth, even, and free of debris. Fasteners should be driven flush except in the case of insulation fastening caps, which project their shape though the membrane.

If the surface is uneven or deteriorated, a layer of fiberboard or thin plywood should be installed first.

Installation Details for EPDM Roofs

After cutting the material to fit, installers use a roller to apply a proprietary contact cement to both the membrane and the substrate. Typically, a length of roofing is set in place and folded in half lengthwise so one half can be glued at a time.

The adhesive should be fully dry on both surfaces before bonding, or bubbles may develop. Also, care must be taken to smooth out wrinkles and air pockets as the two surfaces are mated. Where seams are required, the material is lapped 4 to 6 inches and sealed with either double-faced seam tape or a special adhesive used for bonding rubber to rubber.

At openings, inside corners, outside corners, and other irregular shapes where the EPDM roof membrane has been cut, patches of uncured EPDM are applied using the rubber-to-rubber adhesive. The uncured form of EPDM is highly elastic and can be stretched to conform to irregular shapes.

The material is lapped up abutting walls and serves as its own flashing. Other terminations are usually sealed with an aluminum termination bar or an aluminum flashing covered with a strip of EPDM. Finally all exposed edges of EPDM at laps, patches, and terminations are sealed with a bead of proprietary caulking that protects the edge and acts as an extra water stop. Self-Adhesive.

For small EPDM roof jobs, a few manufacturers offer a peel-and-stick version of EPDM. Installation is similar to standard EPDM but may require a primer on plywood and OSB substrates. Seams generally require a proprietary adhesive with special caulking on exposed edges.

Although the square foot cost is greater than with site glued EPDM, on small jobs labor savings offset the higher material costs.

Pros and Cons of EPDM Roofing

While not intended as a walkway, EPDM works well as a substrate under rooftop decks. Leftover strips of membrane should be used to cushion the roofing from wood sleepers.

Leaks are rare and usually can be traced to sloppy sealing of joints.

Leaks are also relatively easy to identify and fix. One caution is that EPDM can be damaged by grease and petroleum-based products, a potential problem with outdoor grills and spillage of oil-base finishes used on siding or wood decking.

-- Adapted with permission from Best Practices Guide to Residential Construction.

Common Problems in PVC or EPDM Membrane or "rubber" Roofs

EPDM rubber roof installation and repair details (C) Daniel Friedman Eric galow

As Carson Dunlop's sketches ( above and at left below) illustrate, wrinkling and failure at seams are problems to watch for where membrane roofs of EPDM, PVC, or similar materials are installed. A wrinkle in an EPDM roof is also shown at the top of this page.

[Click to enlarge any image]

Common EPDM or Rubber Roof Installation or Wear Defects include


Wrinkles in the rubber roof invite future seam failures

EPDM or membrane roof (C) Daniel Friedman

Shown during its 1998 installation above, this rubber EPDM roof was installed on a New York home by a very large and busy Kingston New York roofing company.

We followed the life of this roof and its leak and repair history for the ensuing 15 years and describe the results here.

The roofer also may have been in a bit of a rush. EPDM needs to be opened and allowed to relax before it is installed, and care should be taken to minimize the number and size of wrinkles in the roof during the bonding process.

A few small wrinkles in the center of a section of rubber probably won't cause much trouble, but wrinkles near EPDM roof seams are an other story, as we explain here.

Wrong roof edge flashing causes ponding

EPDM or membrane roof (C) Daniel FriedmanT

he use of an improper drip edge (gravel stop on a roof that did not use gravel ballast) can be seen at the left side of our photo.

The gravel stop "edge flashing" was nailed on top of rather than below the rubber roof material in order to allow the rubber to be lapped over the roof edge and extended an inch into the gutters (not shown) - which was not a bad idea, though the roof's success then depends on the seam sealing tape (not yet installed here) to prevent leaks at the flashing nails.

The problem with using the wrong roof edge flashing ( a flat drip edge should have been installed) was the ensuing ponding at the roof edge. In New York where ponding of melting snow later re-freezes, the freeze/thaw action worked open seams near the roof edge, especially where a wrinkle crossed any roof edge seal or seam tape seal.

The EPDM roof shown above leaked in less than five years, and by ten years of age we found recurrent openings and leak risks at several seams in the roof as well as along the lower roof edge where that stupid gravel stop was installed.

EPDM rubber roof installation and repair details (C) Daniel Friedman Eric galow

Our photos above and below illustrate what happens when an EPDM wrinkle extends into a roof seam, and as you can see by the water stains, the gravel stop caused excessive ponding that gave frost extra time to work on and push open the seam tape nearer the roof edge. These seam failures (and leaks) began appearing in the rubber roof in less than five years. The photos below show the roof edge at 14 years of age.

EPDM rubber roof installation and repair details (C) Daniel Friedman Eric galow

Membrane Roof Life Expectancy Comparisons

Just looking first at roof material warranty periods, surveying several industry sources as well as the opinions of individual roofing companies, and with the warning that as we discuss at WARRANTIES for ROOF SHINGLES and considering that the warranty offering will pro-rate what you might get in an early roof wear-out by the roof age - reducing the significance of the warranty at all:

Question: which would you choose: silicone membrane roof or a less costly EPDM roof?

Anonymous said: - posted originally at ROOF LEAK DIAGNOSIS FAQs

Another question for my condominium:

One roofer has proposed applying a layer of "silicone roof system" on top of the two layers of modified bitumen (dated 1995 and 2009) as the best fix for one of the building's leaky roofs. The silicone roof system will cost about $14 per square foot. It has a 50-year materials warranty and a 20-year labor warranty.

The board is wondering about this option versus the less expensive (but shorter life?) full tear-out and replacement with EPDM, costing about $10.50 per square foot.

Which option would you choose?

Reply:

Anon:

EPDM, or Ethylene Propylene Diene Monomer roofs are warranted by the manufacturer often for as much as 40 years. Industry gives typically a 22-35 year life expectancy

Silicone is often described as a "50-year" material, though of course how long a specific roof lasts depends on more than the materials, since workmanship, weather exposure, roof construction, slope, maintenance, drainage, etc. are all factors.

Watch out: While various membrane roofing products each has its particular strengths and vulnerabilities (see Paroli 1993), critical in all membrane type roofs is just how well the seams are sealed - that seems to me to be the achilles heel on many flat and low-slope membrane roofs.

In fact some of the most irritating failures on EPDM roofs that I've worked-on and maintained have been in the seam tapes and flashing tapes that are sold to seal EPDM junctures at roof edge flashing - often those products deteriorate in less than ten years. See EPDM ROOF LEAK REPAIRS for details.

Let's apply some guesstimate math to your Silicone roof and your EPDM roof comparison option, JUST using the manufacturer's material warranty offering, and with the caveat that roofing warranties are often more of a marketing text than a surefire guarantee: read the fine print in your warranty, especially about pro-rating, or see this example using WARRANTIES for ROOF SHINGLES

Annualized roof cost per square foot based on materials warranty = INSTALLED COST per sq ft / WARRANTY LIFE

On an annual cost basis alone the two materials look about the same.

But then if you hired a professional to do this analysis you'd factor in probable roof life, your specific roof complexity, flashings, contractor reliability, workmanship, and the trouble of having to go through re-roofing sooner with one product vs. another.

For a more scholarly approach see Equivalent uniform annual cost: a new approach to roof life cycle analysis (Hoff 2006) cited below.

Research on Contemporary Membrane Roofing Material Life Comparisons

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Continue reading at EPDM ROOF LEAK REPAIRS where we describe the maintenance & leak history and the ultimate repairs required for this EPDM roof. or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see

Key Articles About Low Slope & Flat Roofs

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