Is It Normal For A Flat Roof Where The Membranes Overlap To Have A Slight Gap? - Roofing/Siding - DIY Home Improvement | DIYChatroom
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Old 10-03-2018, 09:20 PM   #1
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Is it normal for a flat roof where the membranes overlap to have a slight gap?


I installed a brand new asphalt hot mop flat roof in the beginning of 2015. 1X6 T&G roof deck, replaced some rotted wood, repaired some rafter tails, and all new fascia & metal drip edges.



So 3.5 years later, I noticed there is some softness in the fascia. After I removed the fascia, the 2x4 lumber that's nailed to the rafters were completely eaten up by subterranean termites. Now these 2X4 were brand new lumber in 2015 and now it's totally gone.








The termite company said for subterranean termites to travel so high up, is an indication of roof leaks. Yet this is a newer roof.


I inspected all the fascia around the entire building, and this 20' stretch is the only place where the fascia was "soft". So if there is any leaks, it will be close by there. Inspecting the inside of the house, no stain in the ceiling, no stain anywhere. It's a flat roof so there is no attic.


The only place I can see is there are a few spots where the different layers of the roofing membranes meet, there is a little bit of a gap. Could this be a problem? Even if water enters there, it will be "stopped" by the layer underneath, right?








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Old 10-03-2018, 09:28 PM   #2
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


How would one repair this roof?


When I removed the fascia, as well as the termite damaged 2X4 behind it, there is a 20' stretch of the roof that is damaged.


As I pulled the fascia and 2X4 behind it, I noticed some of the roof deck was also infested. So much so for the first 2" or so, I can reach up with my hand and touch the underside of the roofing paper. The edge of the deck is gone.


In addition, the rafter tails the 2X4 was nailed to, are also heavily damaged I am guessing at least 6", 8" in.


So new lumber will need to be attached to the rafters where it's still solid, a new 2X4 mounted across the rafter tails, new roof deck at least the outer 6" or more, new drip edges, new waterproofing.


For an area like this that is 20' long, not sure how wide to take it back to?
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Old 10-04-2018, 08:54 AM   #3
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


Are we looking at a granule surfaced SBS modified that was hot mopped?
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Old 10-04-2018, 10:54 AM   #4
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


There should not be gaps where water could seep in between the layers.

The hot mopping process or supplemental roof compound applied cold, together with mesh, should seal everything together.
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Old 10-04-2018, 11:35 AM   #5
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


Quote:
Originally Posted by craig11152 View Post
Are we looking at a granule surfaced SBS modified that was hot mopped?

I know it's hot mopped. I am not sure what SBS modified means. I know they put down two layers. There was a guy carrying these hot tar up and down the ladder.


These are some pictures taken by me when the roofer did the job in 2015. It showed the materials they were using.


















I think (not 100% sure) there are two layers of this over the paper. Then some white sand type particles they spread over called "granules".
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Old 10-05-2018, 09:35 AM   #6
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


I believe that is Flintlastic GMS which is a granule surfaced SBS modified made by Certainteed and designed to be either hot mopped or cold adhesive.
You can use a basic trowel grade roofing tar to patch anything on it.

The top sheet came with white granules already imbedded. They probably had a bucket of granules to tidy up overflow hot tar.
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Old 10-05-2018, 02:46 PM   #7
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


If there is a warranty from the installers,call them. Going by the photos, they know what theyre doing. They should be able to fix whatever the issue is.
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Old 10-23-2018, 11:06 PM   #8
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


OK I really need some advice here from the roofing experts. There has been some new development.


A quick recap, I hired a roofing company in 2015 to do a brand new flat roof. I posted some pictures up top in post #5 on what materials and the process they used. I paid $20000 for this roof and it comes with a five year warranty.


I recently discovered termites in the fascia, and after removing the fascia I found they have totally eaten out a 20' section of the fascia, sub fascia, the rafter tails the fascia are attached to, as well as some of the decking closest to the fascia. Termite company said there is no way there is subterranean termites unless there is water penetration, and I said there is no leak inside and this is a 3 year old roof.


The only thing I suspected, was there is an inside corner on the roof where the termite infestation was the worst, and at this inside corner the roof layer has a "bump" and it looks like a pocket, ants were crawling in and out of it. I was wondering if water may be getting under that pocket and attracted the termites. Here are the pictures of this inside corner.










So I called the same roofing company and asked them to come out and give me an estimate for a repair. Tear out the sub fascia, deck, drip edge along this 20' section, sister in new rafter tails, new subfascia, fascia, drip metal, and roofing membrane. At the same time I showed the estimator this inside corner, and I asked him, is this a problem? Could this be the cause of what I am seeing? He said "that's not a problem, but when they do the repair they will redo this corner anyways?" The estimate is $2000 for the repair.


So yesterday was repair day. They tore up the 20' section and I took some pictures.


Here is a picture showing the 20' section they tore up. I put an arrow on the same inside corner I showed in the pictures above.





A closer picture. I can clearly see moisture penetration at that corner. I can see the stain in the decking. I can see the nails closest to that corner are totally rusted out. The most severe termite damages is at that corner.








It seems to be this is a bad original install, which caused water to get inside and under, which then invited the termites in to do it's damages, right? I asked the guy there doing the repairs about his opinion, and he said "No, the termites damaged the wood and roof, then water intruded following damages already caused by the termites". I don't think so, I think it's the other way around, the termite company said the same thing.


Now, they sistered in new short pieces to the rafter tails, two pieces of T&G decking, new sub-fascia, fascia, and laid down the paper...then it rained, heavy rain. We waited for the rain to stop, but everything was wet.





After the rain stopped, they laid the black color roofing tar over the semi-wet paper. They did use a broom to sweep excess water away. Is this OK? I asked them and they said no issue. Then they put on a thicker layer, and applied tar under and over it, plus some granules over the whole thing.








So here are my questions:


(1) I think the "pocket" in the membrane is the culprit for water and termites. It seems like to me it's a bad install, which caused all the problems. I have a five year warranty, they should be doing this repair for free. Am I right or am I wrong? The roofing company dismissed this totally.


(2) Is it OK to lay down the roofing tar over paper that's kind of wet after rain? Moisture won't be trapped under and cause issues?
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Old 10-23-2018, 11:39 PM   #9
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


So how would the termites cause the leak? What was the warrantee for?
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Old 10-25-2018, 07:10 PM   #10
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


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So how would the termites cause the leak? What was the warrantee for?

I don't think the termites caused the leak. My thinking is that inside corner was a poor install and water found it's way underneath and leaked into the deck. It was never noticed because the leak was in the eave area. Then the termites was attracted to the moisture and ate up the rafter tails, sub-fascia and fascia.


The coverage in the contract said:


The roof applied to the building described above is guaranteed for five years from the date of completion upon final payment in full. Under this guarantee, the roofing contractor will, at its own expense, make any repair necessary to correct roof leaks resulting from the following causes:


(1) Failure of roofing felts or base flashing resulting from usual and ordinary effects of wear and weather.
(2) Poor workmanship of roofing contractor in applying roofing and flashing materials.


There are a bunch of exclusions such as Natural disasters, structural failures, change in building or renovations that affected roofing, roof or flashing coating, riots or vandalism, termites, rising nails from beneath.


Even though termites is listed as an exclusion, but to me it seems the leak attracted the termites, not the other way around. But of course, I can't prove it definitely, except the pictures I posted which seems logical to me. That's why it would be nice if roofing contractors on here can chime in as to whether I am making sense or not.
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Old 10-25-2018, 07:22 PM   #11
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


They have worded so there no real warrantee, I would still push him to settle for somewhat less because he can't prove you are wrong either. No I am not an expert.
A termite expert might look at the age of the damage or size to help determine age of damage.
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Old 10-25-2018, 09:02 PM   #12
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Re: Is it normal for a flat roof where the membranes overlap to have a slight gap?


Gap must not be there. In fact, those gaps should have been closed with caulk. It looks like the worker was avoiding possible drips over the side so the tar was thin along the edge. But even then, since entire area was mopped, water should have stopped along the edge, at least as long as tar layer is good. The lumber also looks good, not water damaged.
How did the damaged wood look like? Wet or dry?


I'm not sure if your inspector was right. Termite would follow the wood but go back underground for any water they need. That would be the subterranean termites I know. Wet wood will encourage the termites, but if they started at the ground level, roof is too far away. Maybe you have another kind of termites that don't need moisture. If that's the bug, then the gap wasn't necessarily the problem.


BTW, if the metal in the photo is not a drip edge but more like a gravel stop, I think gravel stop should go over the roofing with tar. Roofing over flashing looks better but I think that edge has more chance of separating from the flashing. Or at least base layer should have been bent over the facia.

Last edited by carpdad; 10-25-2018 at 09:05 PM.
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