Axiom Home Page Forums General Discussion The Water Cooler Calling woodworkers...

Quick question for you wood guys...

Have an overhang (joists and rafters cantilever over the "garage proper" to form a covered patio-type barbequing area by the garage... just removed the buffalo board "ceiling" the original owner put up with 3/8" fir plywood (and installed some extra light fixtures) joists are on 24" centres and the plywood has already swollen and bowed (up between each joist)... it's pretty moist out there tonight, the wood is only primed (and probably still wet from that) with Behr exterior latex primer, and secured with 1 1/4" flooring screws...

Any idea how to fix this/prevent it from happening? Once it dries out and I get a topcoat on it, will that probably help?

Bren R.

make sure overhang is properly vented with either plug type vents or a strip of soffit vent and see if you also have gable end vents or ridge vent so the air can establish a flow....with the joists 24-o/c,you might want to install bridging side to side to add support to prevent sagging

that's too much span for 3/8 plywood. for anything really. put up some stringers on 12" center.

Just over 3 years ago I installed 3/8ths beaded (Wains-coating type) plywood for the ceiling in our 15' x 25' screen room that has 2"x6"s on 16" centers using stainless screws. The thing held up great until I boarded the entire room with plywood during last years hurricanes. Afterwards the seams sagged between each joist and I do believe it was due do not having any air movement for those couple of weeks. So now I'm in the process of removing all of the plywood along with the pain in the butt stainless screws to replace the ceiling with 3" tongue and groove cypress. That's what I get for being cheap to begin with!

I believe for anything outdoors I'd go with something thicker than 3/8th, but keep in mind it is very humid here on the coast in south Florida.

Crap, crap and double crap.

Was looking to save weight, not money by making the last minute decision to go with 3/8 rather than 1/2.

No way for me to get up and do any further framing, so I'll have to switch gears and use something else up there... maybe the same wood siding that's on the garage.

*grumble grumble*

Bren R.

you can always rip 2X4's in half and run them on 12" centers perpendicular to the joists. 1X will work too, but not much meat to nail to. I also agree with air movement.

Luckily once the primer dried, the ply went back to something resembling a regular shape. A bit of caulk to cover the irregularities, bit of expanding foam around the fixture boxes to keep big creepy crawlies out of the fixture, and most importantly - a new day's perspective that from the ground, it doesn't look like the Sydney Opera House like it did late last night from 3" away when frustration factor was high and perfectionism was on it's coattails.

Bren R.

Bren - Is there actually living space over the overhang? Or is it just the roof to the garage? If it's living space you should really insulate that space.

I agree on the suggestion of putting stringers on 12" centers between the trusses though.

Bah - Just read your last post, somehow I missed that before. Ignore the question... If you're anything like me, the more you think about it, the more you'll just want to re-do the whole stinkin' project! I think I should change my signature to read "NeverSatisfiedWithMyHomeConstructionProjects"

It's hard to explain... it's a 2.5 car detached garage sized pad and roof line, the walls form an L - 1.5 car garage and a separate workshop in the leg of the L... the rest of the space is outdoor and is a sheltered patio-type thing, no living space over it, concrete pad under it.

Bren R.