Help Needed! (Roofing)

9 years ago

Hi All,

So I built a shed this weekend, and I did not leave a 1/8 gap between the 5/8 plywood on the roof. I have not shingled or anything yet, but the three 8 x 4 boards are nailed and screwed down in place. The boards are buckling a bit now after some rain.

What's the most reasonable way to handle this? One option is to pull up the boards and re-install with the 1/8 gap, but that will be pretty time consuming and a major pain. I was wondering if I could just cut a 1/8 gap between the boards where they abut with a circular saw set to a depth of 5/8?

Any help is greatly appreciated, thanks!

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Comments (5)

randy427
9 years ago
That would accomplish the intent.
Even with a gap, I'd expect unprotected plywood to swell unevenly, looking like buckling, after being rained on. They may flatten out when they dry, at least to the point where it won't be obvious. (You used CDX, didn't you?)
Scanloni
Original Author
9 years ago
Thanks for the help Randy. I'm honestly not sure if I used cdx. I asked the guy at Home Depot for roofing plywood and he pointed me to Georgia Pacific 19/32 CAT Rated Sheathing. Is that cdx?
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User
9 years ago
Plywood is graded by the face of the material. Since it has two sides, the grading has two letters. Basically the grades are A, B, C, and D.

A is the best level, no defects or repairs.

D is the lowest level and can have unrepaired defects(knotholes/splits/voids/etc.)

A sheet of ply can have faces with different grades---that lowers the cost when one face is not important. An example is AB ply used in cabinet making. The B face is installed on the interior of the cabinet with the A(best) face as the exterior.

X is the designator used for plywood which has water resistant glue and is rated for exterior use. It is not intended top be an exposed surface.

Roof sheathing is covered and does not need to be 'pretty'.

Thus CDX plywood is the least expensive and fine for use.

Plywood companies sell product. They need to have an edge to sell more that the other companies that sell plywood. So, they have sales strategies in order to stand out. Sustainable forests, green products, better glue, and so on.

Oh, I spend a lot of money at various Home Depots, but I seldom trust the person in the orange apron for advice. Many of them know very little about their area of responsibility unless they have been working in that area for years---outside the store.
energy_rater_la
9 years ago
cut it in place. and put some 30 lb felt down so it won't
get wet and swell. osb is ...pieces
glued together, plywood is layers glued together.
google for images

best of luck
renovator8
9 years ago
There will be an APA grade stamp on the plywood.

19/32 CAT is the Performance Category which is simply the thickness.

There should be letter ratings for the two faces (A, B, C or D) The typical grade for roof sheathing is "C-D" (one side C, the other D) Better grades are OK but unnecessary and more expensive.

The moisture resistance classification of the glue should be shown as "EXPOSURE 1" which is commonly called "X". It should not be confused with an "EXTERIOR" glue rating which is not needed for sheathing that will be covered.