What's up with this roof?

[MarkV]

Re: What\'s up with this roof?

Muhammad,

I hate to say it but it does not sound like the ideal system to me. This is not to say that the roof will fail but it does sound like the life of the shingles could be shorter than it should be. The spacing of the sky lights sounds about right for what the plans are telling you. I would guess there is less than 4” of insulation, 1” finish ceiling and ¾” of 1x3. Given that the builder did not stagger the plywood, very basic mistake, VWBill could well be right and they didn’t bother to nail into the purlins either. If that were the case, the 1x3 may have loosened with all the pressure created on that continues seam. This is the time of year, as the moisture content in wood is changing, that things move. Believe it or not, it may stabilize and actually settle back down to an extent.

If you can feel any deflection in the roof at the problem seams, I would be tempted to try and screw it down. Take some measurements to identify the location of the purlins, peel up the tab of a shingle (take a putty knife under the leading edge and break the seal) and drive a couple of long screws about an 1” on either side of the high point. I am not sure this will draw things down completely but it is cheap to try and you would know the 1x3 is attached properly.

Not having continues roof vents makes about as much sense as not staggering the plywood. Given that there is a ¾” air space it might be worth having a continues vent installed now. It could help stabilize the plywood and let you address the rest of the problem when it is time reshingle. A local roofer could install the vent and may be able to see something we are missing at the same time.

Sorry, no great news or easy fix.

MarkV

 

[StoneHeartFarm]

Re: What\'s up with this roof?

Muhammad,

With only 3" of rigid foam, and located in New York, I have to ask the question. Is the house cold in the winter? Assuming you have 3" of something like Tuff-R, your ceiling would only run R15-R18. That's just a wee bit light on ceiling insulation for a Northern climate. (MI Energy Code requires R30 on Vaulteds and the last time I checked Owens Corning they were recommending R38.) The good news on foam is that it actually performs better in colder weather than in hot.

What I'm getting at here is the temperature of the roof sheating. Mositure and temperature are the killers of engineered boards.

The new insulation systems I have looked at include foam with grooves cut on the top surface so that air can flow through on its way to the top vent. Frequently it comes as a SIP panel that already has OSB laminated to it and just has to be hoisted into place.

If the place is cold and you wind up having to redo the roof, you might want to include some extra insulation which could help keep the roof colder in winter (and you warmer /w3tcompact/icons/wink.gif).

SHF

PS. Extra insulation can't hurt, especially if they do to us what I'm afraid they're going to on gas prices. I know it would add to the cost to do the repair, but would it be worth it if your fuel cost suddenly jumped, and the cost to add it later would be a lot higher.

 

[Muhammad]

Re: What\'s up with this roof?

Actually, it's extremely warm, heating costs are reasonable considering the size of the house, and it's always the last house on the road with snow on the roof...

 

[dmccarty]

Re: What\'s up with this roof?

Muhammad,

I was looking at the pictures of the roof again and another
thing popped out at me. Some of the shingles look like they
MIGHT be higher than the others. From the picture it looks
like there are waves in the roof shingles. Now this could be
the angle of the photo and the way light falls on the roof.
The "waves" are running from the left to right.

If the "waves" are there it might not mean anything at all.
What the waves COULD be caused by is the roofing felt
got bunched up in the wind. If that did happen its possible
that there is a leak under the shingles where the felt is not
fulling covering the roof.

Your list of materials used in your roof did not mention felt.

Another 2 cents.

Later...
Dan McCarty

 

[Slamfire]

Re: What\'s up with this roof?

Brian, that sounds like the typical power mad building inspector to me. Plywood isn't any stronger or more stable whether the surface grain is horizontal or vertical.

 

[Robert_in_NY]

Re: What\'s up with this roof?

Yes it is, if you have ever ran it vertical and steped on it between the rafters it will sag quite a bit where as it won't do it horizontal. I have seen roofs where the roofing was ran vertical and you can see every rafter because of how bad the roof saged. OSB is even worse and we only use that if we are roofing over planks so it has a backing.

 

[StoneHeartFarm]

Re: What\'s up with this roof?

Muhammad,

Does your plan specify the type of foam? Just curious, there's so many different types and methods of insulation that it's almost fascinating. Foam is quite versatile, SIP panels, insulated forms, and now SIP panels with rebar to the footing and concrete poured through the panel.

SHF

 

[knucklehead]

Re: What\'s up with this roof?

<font color=blue>Plywood isn't any stronger or more stable whether the surface grain is horizontal or vertical.</font color=blue>

There should be a span rating stamped on each sheet of plywood, something like 16/32, which means the joist spacing for it being laid with the 4' edge across the rafters (or joists), vs the 8' edge across them. Most all construction I have been around has had the 8' edge laid across the joists or rafters for strength, even if the last sheet had to be cut (instead of turned 90 degrees and laid up into the next course). I agree that stability (warp, shrink, etc) shouldn't matter, but I believe it's a matter of how many plies have the grain in the long dimension, or possibly the strength of each ply (cheap stuff on the inner plies, and stronger on the outer).

It's getting harder for me (not a contractor) to see this problem in my mind's eye, but could the skylights have ruined the venting in that area, or have we gotten beyond this in the discussion?

 

[boustany]

Re: What\'s up with this roof?

Actually I thought the same thing at the time, however I eventually came to realize that he was a good guy trying to do a good job.
Plus, I found out that, at least with the 1/2" exterior grade plywood I was using, it is actually strong accross the grain! I made some scaffold 'planks' out of 2x4s and the 1/2" plywood srcaps I had, 24" on center. Anyway, the cross grain ply doesn't deflect much, but the vertical ply does a whole lot!
This doesn't seem to be a problem with 3/4" ply, so maybe it depends on how few plys there are. In any event code says horizontal, so the inspector was in the right.

 

[Inspector507]

Re: What\'s up with this roof?

<font color=blue>.....In any event code says horizontal, so the inspector was in the right...</font color=blue>

Codes are written for a reason, not just personal opinion /w3tcompact/icons/grin.gif