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Capra Aegagrus
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Discussion Starter · #1 ·
I just re-covered a flat-roofed dormer today that runs right into the ridge of the roof. For aesthetics, the previous guy had a row of cap shingles there, glued to the rubber.

I agree that they need to be there for looks, but of course we're not supposed to put those two in contact with each other. Going back tomorrow to finish up. What would you do to make it look good AND last?

Interesting point is, though the old rubber was semi-rotten and poorly installed, it actually seemed to be in pretty good shape where it had been in contact with those shingles for (guessing) 15 years or so.
 

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The chemicals in the asphalt will break down EPDM rubber.

The cap shingles were right at the top of the ridge correct? My guess for the reason the rubber was still in good shape right at the contact point, is the glue used to bond the shingles to the EPDM acted as a decent barrier between the two. But, farther down stream from the cap shingles, where the asphalt shingles "drained" onto the EPDM, it was rotted and deteriorated? Now, you know why....

I agree that they need to be there for looks, but of course we're not supposed to put those two in contact with each other. Going back tomorrow to finish up. What would you do to make it look good AND last?
Personally Tin, I would have used an asphalt product on the flat. Something like a modified bitumen in either a glued down SBS modified or my personal preference, APP torch down modified. You can shingle all day long and twice on Sunday's around modified, because their base chemical make ups are essentially the same.

EDIT: GAF's modified bitumen product is called Ruberoid which is sometimes mistaken for "rubber" roofing. EPDM rubber, is a different product entirely. I'm sure you are aware of this, but I can't tell you how many times "roofers" would come into the wholesale roofing supply house I worked for and ask for some GAF rolled "rubber" roofing..
 

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Capra Aegagrus
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Discussion Starter · #5 ·
The cap shingles were right at the top of the ridge correct? My guess for the reason the rubber was still in good shape right at the contact point, is the glue used to bond the shingles to the EPDM acted as a decent barrier between the two. But, farther down stream from the cap shingles, where the asphalt shingles "drained" onto the EPDM, it was rotted and deteriorated?
Glue-as-barrier is my best guess also, but I'd have to disagree with the drainage causing deterioration. That was too uniform, even 10-12' away from the single stripe of shingles, and in a couple of high spots that wouldn't have received anything of note.

I have to grab a bundle of matching shingles this morning; I'll sniff around while at the supplier and see if anything catches my fancy.
 

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You may be right Tin. I just know what they pounded into our heads every time we talked about EPDM (we sold Firestone and Genflex).... no asphalt, no asphalt, no asphalt.

There might not have been enough shingles to cause any real problems. It may have been with the rubber installation itself.

When they showed us pictures of an entire roof slope draining onto a flat or nearly flat EPDM roof, it was ugly after about three years of life.
 

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It may not be as much of an issue as it once was. Sloped roofs draining on EPDM roofs are fairly common and I haven't seen any more problems with EPDM then with other materials.

They even list details on how to tie the two roofs together.
 

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It may not be as much of an issue as it once was. Sloped roofs draining on EPDM roofs are fairly common and I haven't seen any more problems with EPDM then with other materials.

They even list details on how to tie the two roofs together.
You very well could be right. It's been 12 years since I worked at a wholesale roofing, siding and window supply house. Things sure could have changed.

Sorry Tin, I probably should have included that caveat. :whistling
 

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Capra Aegagrus
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Discussion Starter · #10 ·
They even list details on how to tie the two roofs together.
Yeah, I've seen that here & there, while some still say no asphalt at all. Shingles are different today, and no doubt they continue to tweak EDPM recipes too.

Still, I'd rather play it safe. I wound up using a combination of flashing and silicone so there's no direct shingle to rubber contact, and I'm confident it will hold.

Sorry Brian, no pics. It's an ugly little 8x12 dormer that would blow up my camera if I tried. The owner and I agreed that it was probably built by Uncle Harry for beer--which he consumed while building it.
 

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We where always told never use tar on rubber but you could run your shingles on to the rubber then seal down with water cut off.
 
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