What Happened Here Tile Roof Plywood Decking

Can anyone give me some feedback on what they would report if they saw this. Please refer to photo. Thanks.

Space noted at decking and frame in attic above master closet.JPG

Can’t really tell…Did you stick a moisture meter in it?

Yes. There is no wetness, only space between the member and the decking.

It looks like no spacing between the sheets, were there any H clips installed? No room for expansion. Also was there adequate ventilation in attic? Any bath fans venting in attic? Vapor barrier installed? It will be a major cost to repair with it being a tile roof. Report it as a call for further evaluation and repair estimates. IMO

The bathroom vents are venting at the attic vent. They have them all running right up to the vent. I did not see moisture barriers anywhere. I wrote it up as an item that requires further evaluation but I still would like to understand why there is so much space between the decking and the member. It only appeared to be visible at this location.

It is hard to tell from the picture, but it is probably because when the decking was installed, there was no gap or not enough gap between sheets, as a result when the heat builds up the plywood expands, ir cannot go down because of the trusses, it cannot goes sideways because of other sheets around it, therefore the only path for expansion is up. I have seen this happen many times before, when it gets wet or hot wood will expand. Rock cutters drive a wedge into a slot in granite, then wet it, the expansion will split the rock right where they desire. Hope that explains it. P.S. it never has to come in direct contact with water to do this, humidity will do it, especially here in the south.

How far apart are the nails in that decking. Almost looks like more than 12 inches. What year was that home buit??

It was built in 2002-2004. The realtor said 2002 but there were ARC Faults for the bedrooms that make me think possibly 2004. In the photo where you see the trusses and decking, there is also another truss that you cannot see directly behind the one you see in the photo like it was deliberately installed that way. I called it worthy of another opinion by a professional but threw it out here for other input.

Here are more photos of the accessible attic areas. These trusses appear fine as opposed to the ones in the first photo.

Attic access.JPG

Limited attic access because of size.JPG

Are the rafter spans appropriate for the length, size of member, spacing between, ? The tile makes a really heavy roof structure.

I have seem similar decking problems that are cuased by lack of support in the center of the foundation. If the ends or the house are well supported and the piers or any other foundation element sagg in the middle, it puts the roof deck into compression and will cuase the deck to become “wavy” while it tries to fit into a smaller space. Take a sheet of paper and lay it on your desk, then press the outside edges toward the center. It will bow up just like the decking in this photo.

Good analogy, that is what I was trying to portray.

Many truss systems are designed to span wide areas without the use of piers or other load carrying methods in the middle of the span.

The photo looks as though the sheathing was simply not nailed frequently enough.

That was my opinion too. Simply not nailed. The combination of no nails , along with not enough space between the sheets of plywood for expantion/contraction. We use to use the shank of the nail as spacers.

If that roof was installed in 2004, then the nail spacing is incorrect. The plywood should have been nailed every 6 inches. That applies to the Dade County Building Code. I dont know what you guys are using up in Orlando. It would also depend on the year the permits for the home were pulled.

It looks like the blocking was not installed correctly and is sitting higher than the roof plane, which prevented the decking from sitting on the top of the trusses. It doesn’t seem like that big of a deal.

Trusses are designed to bear only on the outside walls. If the truss bottom chords are actually touching interior walls, those walls have become bearing walls, the truss is carrying load in a manner for which it was not designed and you’re looking at a defective condition.

No way to tell from the pictures, here are the possiblities I see…

  1. The trusses are low for some reason- and that happens, someone forgets a framers plate or some other thing happens- and shot with a nail gun, which will not pull sheathing tight to framing etc.

  2. Bowed plywood was installed and shot with a nail gun.

  3. It was OK when installed but has at some point absorbed enough moisture to make it bow and pull nails loose. In this case the nails should look rusty and moisture stains should be visible. No rust, no stains.

Nailing schedule should be 6" at the perimeter and 12" in the field. Varies with walls, but seldom with roofs.

Kenton, I wonder how that header got to be tight under the plywood and nailed from the opposite side of the rafter?

Looks like the plywood has been like that for a while, or up until someone added this header for something. At least we know that the header was added when the plywood was cambered up.


Marcel :slight_smile:

Weird it is… and not that big a deal. If it were my house I’d probably leave it unless I could figure out any reason it was a real problem.

Yep, being it’s a tile roof, fixing it would be costly. I was curious about that header, too…looks like a “retrofit”, as if bowing occurred and happy Harry Homeowner stuck it in there for support…he just didn’t carry it through. The possibility that it’s a truss problem seems reason enough to refer it, but there should be some related clue somewhere. Shouldn’t there?