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Leaky EPDM rubber roof repair details:
This article describes an EPDM roof installation study & roof repair history spanning fourteen years, from original rubber roof installation (and the mistakes & shortcuts that led to leaks and trouble) to an extensive tear-off and re-roof repair that was made along the entire problem roof's lower edge.
We illustrate how choice of the wrong roof edge flashing combined with wrinkles in the original EPDM installation led to both frequent maintenance and frequent leaks in the original roof.
Tracing the Life & Performance & Repair History of an EPDM Rubber Roof with Installation Mistakes
In general we like rubber roofing material. Modern EPDM is very reliable, tolerates sunlight, temperature variations, and properly installed, we have found it leakproof.
But the performance of an EPDM roof can be very different if the installer is not familiar with or does not follow good roofing practices.
Here we provide photos and comments following study of the performance of an EPDM roof during the first 12 years of its life, assaying the effects of mistakes and poor workmanship in the original installation.
Wrinkles in the rubber roof invite future seam failures
Shown during its 1998 installation above and at left, 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 14 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
The 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.
Our photos above and at left illustrate another problem with the gravel stop used at the lower edge of this EPDM roof - the metal flashing was not wide enough to reach onto the roof decking - so nails that supposedly secured the flashing to the roof were often nailed into an open space between the roof sheathing edge and the fascia board upper edge - into nowhere.
At above right the original roofer must have figured that nailing six nails into empty air would hold the gravel stop in place.
At left you can see as we lift the roof covering that the nails through that gravel stop didn't catch any wood decking.
This lack of secure nailing allowed the gravel stop to lift and buckle, increasing the roof ponding problem. At re-roof time, selecting a flat drip edge that had plenty of nailing width cured this difficulty, as we illustrate below.
EPDM Wrinkles Extend into Roof Membrane Seams, Aggravated by Gravel-Stop Ponding
Our photos 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 near 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.
Interim Roof Repairs Avoided a Leak Catastrophe in this EPDM Rubber Roof
We made some interim EPDM roof repairs by cutting out the worst wrinkles and gluing down new sections of EPDM roofing material over the cutout. But as more of the original work deteriorated, by the end of a decade and after discovering carpenter ant infestations traced to leaks near the roof edges, we just didn't trust this roof further.
We inspected this roof every year, sealing suspect seam edges by cleaning the plies and applying rubber roof seam sealer. But as our photo at below left illustrates, it was an endless task, exacerbated by that damnable gravel stop. At below right shows another of the original roofer's ideas for roof-wall flashing: "run it up the wall and glue the top edge of the rubber to the wood siding" - not a reliable installation and one that required constant attention.
Pounding the gravel stop "flat" to allow the roof to drain provided emergency relief to slow the frost working away at seams near the roof edge, but it left a horrible, ugly, and equally stupid roof edge flashing installation.
Beneath a section of garage roofing installed by the same contractor we found leak stains during interior renovations (below right) that were traced to a roof edge (and thank you gravel stop) leak that was hard to spot from outside. At below left I'm pointing to the soil staining in this small ponding area right over the leak shown at below right. We found a nice nest of active carpenter ants (photo) in the wall structure in this area. Leaks into an enclosed roof cavity mean that the space stays wet for a long time - a standing invitation to wood destroying insects and sometimes mold contamination as well.
Finally we just gave up on the annual cut and patch job on this roof. In 2012, after 14 years of cut and paste interim repairs, a better solution was provided by our associate, Eric Galow, of Galow Homes.
Preparing an EPDM Roof for Repair
Galow's crew cut and removed the EPDM and ugly gravel stop from the entire lower roof edge, cleaning and blowing off all loose fragments of debris (below left) and peeling back a 6-inch section of the original roof that we would glue-lap over a new EPDM section of roofing along the roof's now exposed surface. (Photo, far left).
Eric also installed the proper drip edging, of adequate width to nail to the roof deck back from the edge, with a flat profile - no more raised edge gravel stop to cause roof edge ponding. (Photo at near left).
The new sections of EPDM were opened flat and allowed to relax in the incredibly hot sun (photo below left). The new material was fully adhered in place (below right) gluing half of the length of rubber at a time then gluing and smoothing into place the second half, working with care to avoid wrinkles.
Keeping the EPDM Roof Smooth and Wrinkle Free During Installation
Notice how nice and smooth the installer has made the new EPDM? No wrinkles in this fully-adhered rubber roof repair.
At the right side of this photo you can see the second segment of rubber roofing half-bonded in place and with end seam overlap primed and ready to adhere as well. We used bricks to hold back the to-be-overlapped width of original roofing during this application so that all final seams would be lapped and glued in the proper direction.
Above Ron is bonding the lap-over length of original roofing onto the upper edge of the new EPDM that has been run along the roof edge. That extension cord visible in the left photo was powering the leaf blower used to keep debris off of the to-be-glued surfaces.
Can You Really Fry an Egg on a Hot Roof?
Below you can see the scientific mind of the crew at work - it was so hot on this roof that several of us thought you could "fry an egg" on the roof surface. So we tried it.
Keep Debris Off of EPDM Roofing During Bonding
That extension cord visible in the left photo was powering the leaf blower used to keep debris off of the to-be-glued surfaces. At below right you can see we used our bricks to hold the overlap seam of original EPDM down flat onto the new EPDM repair-surface during glue drying time.
Following this EPDM repair we visited all of the existing seams on the remaining original roof (upper slope sections), cleaning and re-sealing any seams that appeared at all suspicious. We also closed and sealed (or re-sealed) all of the EPDM seam edges with EPDM lap sealant as a final step.
(Aug 15, 2012) jerry d said:
roof wrinkle was cut out and patched repaired. will the patch added hold against rain over several years?
Yes if properly installed. The surfaces had to be clean and dry and the proper adhesive used.
(June 30, 2014) J Haynes said:
My roofer has just installed a new EPDM flat roof which 'ponds' over about a quarter when it rains. He says that this is normal. Is he right as the only way the water is displaced is by evaporation?
Well not exactly ...
"Flat" roofs usually are very low slope and do indeed drain to a scupper, roof edge or other drain opening. They are not very often perfectly dead flat.
IF your roof has no standing water 24 hours after rainfall then it's considered to drain adequately.
Otherwise it is not draining adequately.
Question: drip edge specifications for flat & low slope roofs
(July 28, 2014) Hal said:
I have a elastomeric roof with APOC 252 white on top of APOC 302 emulsion. The previous roof had a 2" gravel guard and the elastomeric is failing in the joints of the guard and the roof. Water is getting behing the fascia and rotting it. The roof is 5/12 pitch.
Planning on cutting back the fascia. shall I cut the fascia just below the coating level? It feels like I need a connector between the fascia nd the roofing material. Any suggestions?
Hal we had this problem on an older EPDM roof, exacerbated by the presence of a gravel guard (with a raised edge) that kept water on the roof where it should have been allowed to drain. Gravel guards belong on tar and gravel roofs, not EPDM or elastomeric roofs.
After several annoying years and seeing the EPDM begin to lift at roof edges our solution was to cut back 12" of roofing from the lower roof edges, remove the gravel guard, install the proper (flat) roof drip edge, then glue down a new length of EPDM along the roof edge and atop the upper portion of the drip edge. You can see that repair in the article above on this page.
The drip edge should extend out about 1/4" from the fascia (vertical) surface so as to direct water off of the fascia rather than onto it.
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"Choosing Roofing," Jefferson Kolle, January 1995, No. 92, Fine Homebuilding, Taunton Press, 63 S. Main St., PO Box 5506, Newton CT 06470 - 800-888-8286 - see http://www.taunton.com/FineHomebuilding/ for the magazine's website and for subscription information.
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