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Old 02-11-2012, 11:29 PM   #1
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help! strange horizontal bubbles on new roof


Last September, I had my roof re-done after some hail damage. Besides the hail scars, the original roof looked normal from the ground. I basically had it replaced b\c my insurance said that it needed to be replaced.

The roofer is a local guy with a good reputation and a is long standing BBB member with a clean record. I genuinely believe he's as confused/upset about what's happened since as I am, but I'm hoping to get some objective opinions from you guys nonetheless. I fear this could turn ugly if somebody has to reach for their wallet.

His crew removed the original, checked the decking, removed the ~5 year old 3-tab shingles (original roof on a ~5 yr old house) and put down 30lb Owens Corning Fiberglass reinforced felt (I have a fairly steep [8/12 pitch] roof) and then 25 year Owens Corning 3-tab Supreme Shingles. They did not remove the original felt, though from what I gather that's pretty rare around here. All the original vents were replaced with new ones of the same type/size.

Anyhow, not long after the job was done my wife started complaining that it looked kind of sloppy. The roofer had warned me that we had a couple of high rafters, so I waved her off, thinking that it was more of a framing issue than a roofing issue. In hindsight though, I think I was struggling to admit that I might have a larger problem that needed to be dealt with.

Eventually, I started to realize there were alot of horizontal bubbles in the roof (conspicuously at regular intervals), in addition to a couple of vertical issues that I suppose could be due to high rafters.

Here's a picture:

(I'll get some more tmrw without the sun blazing in your eyes). This is the North facing side of the house which exhibits the problem most prominently, though it's also happening else where. It just happens that this is the side of my roof most visible from the street as well because of where we sit on a curve.

I went ahead and sent this photo to my roofer to see what he thought. At first he just acknowledged that it looked unusual and wondered if I'd been having any foundation issues. Then he asked if I'd modified the insulation or ventilation in any way. The answer to both questions was no.

He then came by the house and I even took him into the attic to show him that my soffit baffles were unobstructed and my plywood decking was not buckled and had the proper clips, etc. We walked around the interior so I could show him that there weren't any cracks or signs of foundation issues. I could tell he was starting to worry as well.

Anyhow, he then contacted his materials distributor and Owens Corning and had them take a look at the photos. They also suggested potential issues with ventilation being insufficient/becoming obstructed and foundation issues. Ultimately, some folks from OC came out to my house with the roofer and took more photos and even walked around on the roof.

According to my roofer, the bubbles are literally just that. When you press on them, the shingles flatten down. There is no decking pushing up on the shingles, just air. Even the high rafter theory is strange for the vertical defects because usually aren't those smoother? I mean if a high rafter is pushing up decking and that's pushing up the shingles, you'd expect a smooth hump, not a jagged ridge. My roofer is still totally puzzled, but he says the OC folks are going to run it by one of their experts in Ohio. I have no idea where that will go (or when)

So, has anyone ever seen this before? Any solid theories on what's going on or questions I can answer to help solve the mystery? I'm not planning to be in this house for much longer, so I really want to get this solved before I find myself trying to sell a home with a butt ugly and potentially physically defective roof.

The only thing that really changed from the original roof to the new roof (besides the roofers) is that the new roof went on top of the old felt (likely 15lb since it was a builder's roof) with the new 30lb felt on top of that. I'm wondering if that doubled moisture barrier has now become "too effective" at sealing air flow as well. Is it possible that the felt is blowing up along the decking seams like a balloon? What scares me is that this roof hasn't even seen a hot Texas summer yet. Does anyone think it will get better with the heat?

I'd appreciate any help you can give me! Thanks in advance.

-BC
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Old 02-11-2012, 11:42 PM   #2
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help! strange horizontal bubbles on new roof


I see no way it would be the doubled up felt.
I would have taken some of those shingles off and cut back the tar paper over the raised areas and look at the sheathing to see what it's doing to cause this.
Looks like the lines are following the seams in the sheathing.
I've seen many older houses with no ventalation and there not doing this.
It's nothing to do with a high rafter or the house moving.
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Old 02-12-2012, 04:58 AM   #3
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help! strange horizontal bubbles on new roof


I wonder of the expansion clips were left out when the sheathing was done.


Did a Google search and wouldn't you know one of the top hits was DIY Chatroom Thread


Looks like the bumps are about 45" apart which would suggest the plywood vs the felt (36"?).


Woops! Re-read your OP. Looks like the edge clips are installed


Still think its a sheathing issue though. Searching now for Interior vs Exterior Grade OSB. Interior Grade edges absorbing humidity and swelling?
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Last edited by CplDevilDog; 02-12-2012 at 05:06 AM. Reason: Stupidity
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Old 02-12-2012, 06:28 AM   #4
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Read this one---it covers every possible cause of your problem--Wavy Roof! Need Opinions/advice - Roofing - DIY Home Improvement | DIYChatroom
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Old 02-12-2012, 09:21 AM   #5
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help! strange horizontal bubbles on new roof


I bet this one will be blamed on OSB too........... Oh wait, this one is plywood, and he also said the bumps can be pushed down by hand........
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Old 02-12-2012, 09:23 AM   #6
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help! strange horizontal bubbles on new roof


Quote:
Originally Posted by dfwnewroof View Post
The only thing that really changed from the original roof to the new roof (besides the roofers) is that the new roof went on top of the old felt (likely 15lb since it was a builder's roof) with the new 30lb felt on top of that. I'm wondering if that doubled moisture barrier has now become "too effective" at sealing air flow as well. Is it possible that the felt is blowing up along the decking seams like a balloon? What scares me is that this roof hasn't even seen a hot Texas summer yet. Does anyone think it will get better with the heat?

I'd appreciate any help you can give me! Thanks in advance.

-BC

You are on the right track here.
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Old 02-12-2012, 12:51 PM   #7
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help! strange horizontal bubbles on new roof


Thanks all. I actually read the 200+ posts in that Wavy thread before starting this one. Since I've got plywood (not OSB) with expansion clips, and the bubbles push down by hand, I don't think it's the decking/sheathing this time.

I suspect the reason the bubbles are so regularly spaced with the outline of the plywood is that this is where air is forcing through the gaps in the boards and pressing the felt upwards.

MJW, so you agree that there's too much felt and it's creating a pressure issue? I didn't have any of this on the original roof, so could extra felt actually induce a ventilation issue?

Should I be adding soffit vents or talking to the roofer/Owens Corning about the materials used for the job? Should I have expected them to remove the 15lb felt during the tear off and is it commonly known that there are times when too heavy a grade of a felt is bad thing?

Any suggestions for how to resolve, without requiring a re-roof?
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Old 02-12-2012, 01:57 PM   #8
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help! strange horizontal bubbles on new roof


I think it has something to do with the 30 lb paper. It doesn't breathe like 15 lb.

Besides that point, I believe the real problem is too much moisture and/or heat in the attic....and it is because of the lack of ventilation and/or insulation. Actually it could be a whole list of problems. You just need to find out why there is so much heat and humidity up there.

I know that sounds like a broken record. Everyone blames everything on insulation and ventilation.....but these types of problems are showing themselves more and more. Most of it has to do with the more strict energy codes nowadays, JMO.
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Old 02-12-2012, 02:04 PM   #9
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Quote:
Originally Posted by MJW View Post
I think it has something to do with the 30 lb paper. It doesn't breathe like 15 lb.

Besides that point, I believe the real problem is too much moisture and/or heat in the attic....and it is because of the lack of ventilation and/or insulation. Actually it could be a whole list of problems. You just need to find out why there is so much heat and humidity up there.

I know that sounds like a broken record. Everyone blames everything on insulation and ventilation.....but these types of problems are showing themselves more and more. Most of it has to do with the more strict energy codes nowadays, JMO.
I agree. I also believe that under certain conditions, humid air is drawn in through soffit vents and condenses on the bottom of the sheathing before it reaches the upper exhaust. It's just a theory, but I think it can happen under the right conditions, such as after a warm winter day, when the roof deck cools on the exterior before it cools in the ventilation space.
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Old 02-12-2012, 02:09 PM   #10
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Quote:
Originally Posted by loneframer View Post
I agree. I also believe that under certain conditions, humid air is drawn in through soffit vents and condenses on the bottom of the sheathing before it reaches the upper exhaust. It's just a theory, but I think it can happen under the right conditions, such as after a warm winter day, when the roof deck cools on the exterior before it cools in the ventilation space.
You posted about that in another thread about ice dams. It made a lot of sense. Look at the pic, this one is brick also....

Usually when you see condensation in the attic, it's on the north side, and that's what it's showing.

Wonder what the south side of the house looks like.
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Old 02-12-2012, 02:29 PM   #11
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My neighbor's two story is right next to us on the South Side, so it's hard to get a good vantage point. Nonetheless, I got up on the fence and snapped these shots of the south side. I can definitely see some bubbles, though the vertical ones are most apparent because of my angle. In general it doesn't appear to be as prevalent on this side.

If it's a heat/humidity thing, are you saying that the condensation is causing the decking to move OR are you just saying that as the roof heats up again, that moisture is converted into vapor which makes bubbles?

It appears I can get a thermometer/hygrometer combo for not too much expense. If I had one though, what would I be looking to prove? That the attic humidity and temp is significantly higher than the outdoor readings as the temperature starts to drop around sundown?

If I do find that I've got alot more heat/humidity in the attic, would I then need to add insulation to keep the house from warming the attic so much? Or should I be looking for more ways to get the air flow from the soffit vents to the vents on the ridge?



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Old 02-12-2012, 02:40 PM   #12
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help! strange horizontal bubbles on new roof


Your problem is the felt. I have seen this when felt has not dried after being wet, either when placed on the roof or even before.
Most roofers know enough to use a knife when installing to slit the felt paper to help it flatten out.

Most likely, in my experience it will flatten out over the next two years.
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Old 02-12-2012, 02:54 PM   #13
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Thanks. I do recall that we had a light shower (the first in months, actually -we had a terrible drought last summer) the morning of the tear-off. The felt was just sitting in my driveway on the roll at that time. I figured that might affect the exposed layer, but not the whole roll. I actually asked the roofer about it that day and he said it was fine. How do you explain that the bubbles seem to occur right on the seams of the decking though?
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Old 02-12-2012, 03:26 PM   #14
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You have a pressurized attic with air trying to escape anywhere it can. The power vents are contributing to the problem, read page 3 especially; http://www.wag-aic.org/1999/WAG_99_baker.pdf

The attic floor needs air sealing to stop the basement/crawl air from helping the problem. Power vents can cause problems; http://www.advancedenergy.org/buildi...%20Studies.pdf

Notice fig. 5 on fan pressure: http://www.wbdg.org/resources/airbarriers.php

The roof papers could be wetting from the brick air space moisture driven to the roof space- not blocked, especially after a rain on the south side; http://www.buildingscience.com/docum...n-brick-veneer

I'd want to check the south walls after not using the power fans a few weeks. Course, it could be either one or just the attic air sealing lacking....

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Old 02-12-2012, 04:22 PM   #15
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I don't have any power vents and my home is only 6 years old. Do you really think that paper is relevant to my situation?

I have soffit vents along the overhangs on the north and south sides which are baffled in the attic to prevent the loose insulation from obstructing them. Then I have a variety of roof vents near the ridge (turtle and box vents).

To be clear, are you saying that I never had sufficient ventilation and the addition of the 30lb felt was the tipping point?
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