What's up with this roof?

[Muhammad]

What\'s up with this roof?

A picture is worth a thousand words. /w3tcompact/icons/smile.gif (View the attached photo to see what I mean.)

This has developed on my roof over the past couple of years... started as just a small line of shingles being lifted and has progressed to what you see in the photo now. Front of the house doesn't have this problem, just the rear.

I'm not the original owner and hence, don't know for sure what was done originally, but it's a multi-layer roof. The original building plans that I have don't indicate what the plywood was fastened to originally. I understand the shingles were replaced about 7-10 years ago (house is 27 years old).

The roof above the garage that I can gain access to from the inside (stick built) does show that the plywood wasn't staggered, since the seams are lined up. No such problem on that side, but the plywood is fastened to rafters directly.

Seems to me that based on what I can see, the plywood is curling underneath the shingles, since the spots are about 8' apart... it's also easy to assume that the plywood wasn't staggered on this main portion of the house either, because of the way the shingles are lifting.

Anyone have an idea as to what's happening, and why?

Thanks in advance for any thoughts.

 

[knucklehead]

Re: What\'s up with this roof?

Well, you're probably right. If my Father is lurking out here anywhere, he'll probably confirm it, since he's seen more houses in their underwear than most people.

Dad???? Not You, Muhammad /w3tcompact/icons/grin.gif

 

[manganos]

Re: What\'s up with this roof?

Looks like the plywood is warping. I just had my roof replaced this year and some of mine was doing the same thing. The 8' spacing is a dead give-a-way . Roofing is one thing I rather not do myself!

 

[DocHeb]

Re: What\'s up with this roof?

I believe the plywood had been installed without the required spacing between the sheets, and expansion buckles the sheets (just like concrete on a hot day).

 

[MikePA]

Re: What\'s up with this roof?

I agree with docheb, there's probably not enough space between the sheets of plywood and when the sheets expand, since they're touching and have no where to go they buckle. What direction does the roof with the problem face, north, south, east or west? When they installed the roof on our barn, they used spacers that look like the letter 'H' between all the sheets of plywood to ensure they were far enough apart.

 

[Dozernut]

Re: What\'s up with this roof?

Muhammad
Two possibilities on your roof but I am afraid you will not like them. 1. When your roof was sheathed they did not allow for expansion and butted the decking material tight. Wood expands and contracts, your roof decking has most likely taken on the ambient moisture from the air and expanded. Since it was butted tight it only had one way to go and that was to curl up. 2. Check the spacing on your roof trusses. Too far apart and the weight of the roofing materials will cause the sheathing to sag and cause the ends to raise up. Snow load will increase this. The bad news is that you will need to tear off all your shingles and roofing materials to repair these two problems mentioned above. Once your down to just the sheathing you might have to take off the old sheathing and replace it with new, making sure you leave a gap for expansion. The proper thickness of sheathing might not have been used, resulting in a weak roof. Quality builders use the properly specified material and building practices. Unfortunately Some contractors are not forthright and honest and build as cheaply as possible and hire inexperienced help. Check your better business bureau for legitimate roofing contractors or ask at your local building center. If the roof is not leaking and you can put up with look of it, you can probably get a few more years out of it. If you have a leak it needs to be repaired now. A properly done roof with fiberglass shingles should have a life span of 20 years or more. Storms with wind or hail will significantly shorten the life of a roof causing much sooner replacement.

 

[Dozernut]

Re: What\'s up with this roof?

Mike
I would not have replied if I had seen your post. Unfortunately I type slow, so I was slow getting out of the gate. /w3tcompact/icons/blush.gif

 

[MikePA]

Re: What\'s up with this roof?

Dozernut, you added the possibility of the rafter spacing being too wide. I hope for Muhammad's sake, it's not that. /w3tcompact/icons/shocked.gif

 

[Carl_NH]

Re: What\'s up with this roof?

Moisture, cathedral ceilings, along with improperly spaced plywood as mentioned before.

The garage minimally heated and without moisture content reduces the issue, as well if the "front' side is facing south this heat removes the moisture produced from the house thus the buckling effect.

Carl

 

[patrickg]

Re: What\'s up with this roof?

Muhammad, Don't rely on our guesses. This could be anything from a very serious structural problem to just a minor cosmetic problem. You need to get a look at one of the troubled sheets of sheathing. Then you can determine if you have a severe problem, like moisture from inadequate ventilation or whatever causing delamination at the ends of the sheets of ply. If it isn't a moisture problem, give thanks and consider how long it took to get this bad and how long it will take before you must do something to prevent bad consequences.

It is conceivable that you could run a skill saw, properly adjusted, up the joint and make some clearance. Might require mulltiple blades (thin dado type effect) to do the job. You might be able to turn the ply over when re-roofing and reuse it but that is just a maybe.

The important thing is not to decide based on speculation but get in there and do some exploratory surgery to determine the root cause and whether or not it is more than cosmetic.

There are shingles guaranteed for 45 years and (sorry for memory fault in my wet ware) either 100 or 200 MPH winds. Been a couple weeks since a builder told me about them.

Best of luck and please let us know what you find out.

Patrick