Self Adhered Modified Bitumen Install Advice-base & Cap Lifted At Roof Edge - Roofing/Siding - DIY Home Improvement | DIYChatroom


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Old 07-02-2013, 02:15 PM   #1
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self adhered modified bitumen install advice-base & cap lifted at roof edge


Hi! I have just had mule-hide self adhered modified bitumen sbs installed on a low slope valley area of my roof. The area was first supposed to be built up with a cricket/saddle? to 2/12 slope & then plywood put over new slope & 2 ply product installed over that.
The base and cap sheet were left unadhered at least 5 inches from edge of roof so that there is a gap. It looks ugly as H--- but I was told performance wise it would be ok because a pan was installed underneath to keep the water out. Other areas of install area feel spongy as if the product is not stuck completely to the deck especially where the low slope area transitions to the sloped areas-was told that this was ok and necessary so the product would be able to move with the roof or else is would tear. Any low slope roofers or roofers experienced with this product have any advice or know if the above is correct. If not , what should I have done to correct it.
I have attached pictures of the finished install & the original low slope area that had previously been shingled before the cricket/saddle was added.
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self adhered modified bitumen install advice-base & cap lifted at roof edge-unattached-membranes.jpg   self adhered modified bitumen install advice-base & cap lifted at roof edge-self-adhered.jpg   self adhered modified bitumen install advice-base & cap lifted at roof edge-area-before-cricket-build-self-adhered-mod-bit-install.jpg  

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Old 07-02-2013, 02:23 PM   #2
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self adhered modified bitumen install advice-base & cap lifted at roof edge


Where's the drip cap?
No one bothered to strip prime and paint or better yet cover that fascia with coil stock before the roof went on.
Any reason why the shingles were left short with not enough over hang?
Valleys should have been wider at the bottom then the top.

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Old 07-02-2013, 05:14 PM   #3
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self adhered modified bitumen install advice-base & cap lifted at roof edge


This is called a Gusset where I live. The membrane should not be bridged. I suspect that the release paper was not properly segmented and they did not work from the angle changes outward. I would have run the Modified Bitumen up slope about 16 inches to both sides of the gusset and left one foot of exposed cap sheet, before I started my shingles. Both plies should have been run from the bottom of the gusset up slope in shingled fashion. I would have started with a half sheet on the base ply to stagger the joints.

The rake to the right should have been boxed in and covered with sheet metal which runs up under the mod bit. The gap between the sheet metal and mod bit should not be there in my opinion, and I would have hung the mod bit cap sheet an inch past the metal flashing to serve as a drip edge.
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Last edited by jagans; 07-02-2013 at 05:17 PM.
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Old 07-02-2013, 06:16 PM   #4
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self adhered modified bitumen install advice-base & cap lifted at roof edge


Quote:
Originally Posted by joecaption View Post
Where's the drip cap?
No one bothered to strip prime and paint or better yet cover that fascia with coil stock before the roof went on.
Any reason why the shingles were left short with not enough over hang?
Valleys should have been wider at the bottom then the top.
The shingles were previously installed by another roofer. They were removed for this work to install the self adhered mod bit and new shingles put on back on so I am guessing they were put on to line up with the existing shingles. Why should the valley be wider at the bottom than the top?? The valley is wider where the 3 slopes meet and narrows as it goes toward the roof edge to drain.
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Old 07-02-2013, 06:34 PM   #5
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self adhered modified bitumen install advice-base & cap lifted at roof edge


Quote:
Originally Posted by jagans View Post
This is called a Gusset where I live. The membrane should not be bridged. I suspect that the release paper was not properly segmented and they did not work from the angle changes outward. I would have run the Modified Bitumen up slope about 16 inches to both sides of the gusset and left one foot of exposed cap sheet, before I started my shingles. Both plies should have been run from the bottom of the gusset up slope in shingled fashion. I would have started with a half sheet on the base ply to stagger the joints.

The rake to the right should have been boxed in and covered with sheet metal which runs up under the mod bit. The gap between the sheet metal and mod bit should not be there in my opinion, and I would have hung the mod bit cap sheet an inch past the metal flashing to serve as a drip edge.
I was told the 2 plys run up slope on all sides at least 12 - 16 inches and the shingles are over top where it runs up the slopes.

The contractor doesn't seem to be concerned that there is a bridge or gap where the mod bit is unattached from the roof deck. They say it is ok since there is a pan installed underneath. I am thinking that the product will start to delaminate and fail. They want to complete it by taking a heat gun to seal the open end down but it still will not be adhered to the deck completely from the sealed end to at least 5 inches back on the roof. They want to fix right side by putting some kind of metal flashing or edge along the fascia board and just under the shingles.
I just don't think it should be unattached anywhere where it is covering the roof deck.
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Old 07-03-2013, 12:32 PM   #6
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self adhered modified bitumen install advice-base & cap lifted at roof edge


Quote:
Originally Posted by cgeorgette View Post
I was told the 2 plys run up slope on all sides at least 12 - 16 inches and the shingles are over top where it runs up the slopes.

The contractor doesn't seem to be concerned that there is a bridge or gap where the mod bit is unattached from the roof deck. They say it is ok since there is a pan installed underneath. I am thinking that the product will start to delaminate and fail. They want to complete it by taking a heat gun to seal the open end down but it still will not be adhered to the deck completely from the sealed end to at least 5 inches back on the roof. They want to fix right side by putting some kind of metal flashing or edge along the fascia board and just under the shingles.
I just don't think it should be unattached anywhere where it is covering the roof deck.
You have what I call a snow trap. Since you are in VA it might not be a problem, but I can visualize that entire area filling up with snow, so that entire area should have been covered with ice dams protection membrane before the shingles were installed. My opinion regarding your situation has already been stated, so I am not sure why you are repeating what the contractor said. I don't care what your contractor said. You should not have bridging. To eliminate the chance of blistering it is much easier to use cold process adhesive, and two plies of modified. Ply 1 glass based, sanded both sides Ply 2 polyester based, sanded bottom side granular surfaced, cap. These can be adjusted after they are placed. The use of adhesive also helps to eliminate the possibility of air entrapment and blistering. It does not make sense to run the shingles all the way down on the sides when this entire area is out of the sight line. What sense does it make to nail through a waterproof membrane? Nails make holes. Holes are potential leaks.

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Last edited by jagans; 07-03-2013 at 12:38 PM.
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