Plywood and bowing - storing?

[wd4lc]

First off, my apologies if this isn't the correct forum for this question. It seems a bit like an amateur hour question so I figured it would fit in with the "stupid question" theme.

I purchased a 4x 8 sheet of 19/32" RTD sheathing. I used a portion of it as a hinged (accessible) roof on an animal house. This was primed/painted on the underside and the top was coated with an asphalt roof coating. After a couple of weeks I started setting this out into the sun (in the down and also in the up position) so that the roof would cure. I noticed that the roof started to bow very noticeably. I thought perhaps this was because of the coating. However, I noticed that the remaining pieces of the unused sheathing of which I had stored vertically were also bowed very dramatically (side note - the T1-11 was stored vertically and was perfect).

Is this preventable. Would these have stayed straight if I had stored them laying flat and if I had kept the roof closed? I've basically just wasted half a sheet of the stuff. If it's not preventable then perhaps I need to look for another type of product for my roofs. If it is preventable then I'd like to get it right next time. Thanks.

[cabinetman]

The best way to store plywood is flat. Some of that bowing may be unpreventable.
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[jabe]

I'm with cman, store it laying flat. Storage is always an issue with us and laying it flat takes up alot of floor space. If you can design a shelf hanging from your rafters & wall studs in your work area so you can store your plywd flat on it so it will not take up floor space can be a solution.

[wd4lc]

Thanks cman and jabe. I'll give it another whirl and this time store it flat. Also, I'll make sure to keep the roof closed while the asphalt cures on it in the sun.

Always good info, thank you.

[Mr__Bill]

Another thing to consider is, sheeting is normally nailed down and as such in the manufacturing process not a lot of care is given to balancing all the stress that leads to warping and other origami moves.

When you visit the borg you may note that the top sheet on a pile is starting to warp while those under are still flat. If you take one from underneath it too will warp as soon as one side starts to dry faster than the other. I have had the best luck with plywood both the good stuff and the rest, storing it on edge in a frame that holds it flat. This can be as simple as against the wall with several 2x4s clamping it against the wall studs. The bottom line is however, goods manufactured as sheeting are likely to warp no matter what you do, so one thing that is possible is to take two pieces that are warping and glue them together with the warping counter to each other. If you press them down flat when the glue dries they stay sort-of flat with the stresses counter balancing each other.

Bill
concrete is getting spongy and the aluminum is starting to rust, sure wish summer would come.....

[wd4lc]

Another thing to consider is, sheeting is normally nailed down and as such in the manufacturing process not a lot of care is given to balancing all the stress that leads to warping and other origami moves.

When you visit the borg you may note that the top sheet on a pile is starting to warp while those under are still flat. If you take one from underneath it too will warp as soon as one side starts to dry faster than the other. I have had the best luck with plywood both the good stuff and the rest, storing it on edge in a frame that holds it flat. This can be as simple as against the wall with several 2x4s clamping it against the wall studs. The bottom line is however, goods manufactured as sheeting are likely to warp no matter what you do, so one thing that is possible is to take two pieces that are warping and glue them together with the warping counter to each other. If you press them down flat when the glue dries they stay sort-of flat with the stresses counter balancing each other.

Bill
concrete is getting spongy and the aluminum is starting to rust, sure wish summer would come.....

Thanks Mr__Bill. It sounds like I shouldn't expect it to keep its shape no matter what I do but that there are measures to help at least somewhat limit the warping.

I like that idea with the 2x4's. This is another good reason for me to buy some clamps!

That is a great point about it normally being nailed down. That had crossed my mind today and I thought perhaps the roofing would have kept it's shape better if it were nailed down (as most roofs are) instead of it being hinged. I was also thinking that the liquid asphalt coating on the roof probably didn't help matters as that absorbs heat and perhaps that had something to do with it.

Something else I learned this evening as I purchased another sheet of sheathing....plywood prices apparently fluctuate more than I had thought. I bought this same sheet a month ago for $5 less.

Anyway, I'm storing these flat. I'm also going to make sure that something is always draped over it.

Thank you.

[Mr__Bill]

I have been thinking about that black roof coating. It's going to make it a bit hot inside on sunny days. It may also be a mess when the dogs get on top. You may also want to have a way to latch it down so that the warping is not such an issue. Loose pin hinges and a hitch pin make for an inexpensive put secure way to hold it down.


Bill

[phi1l]

I have found it best not to store plywood & where ever possible when using it, G&S it to something that is jointed flat.

[herb fellows]

Unfortunately, as someone here uses as their signature, 'plywood doesn't warp like wood; it warps like plywood'. Sometimes I think no matter what you do, in the end you just have to get lucky!

[cabinetman]

If you have limited space, and can't store flat. Stand it against the wall on a long edge (whatever the size). Cut some strips of wood to act like a spacer to put under the edge to keep it off the floor, especially a concrete floor. They don't have to anything special, 3/4" x 2"-3", or as long as necessary to fit under multiple sheets (perpendicular to the sheets). Have the plywood as vertical as possible. IOW, as little angle to the wall as possible (preferably flat to the wall).

If a frame is made as Bill suggested, that the sheet(s) could be clamped to, that would help. If the sheet has a bow, set the bow towards the frame, and clamp, so the clamps will flatten the sheet.
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[Kristofor]

If you just used a loose piece of plywood hinged at the peak you may have better luck if you can somehow accommodate a frame (even something light) around the perimeter on the underside of the panel. This then gives you something to screw/glue into and as those members are unlikely to want to move in the same way as the plywood it should help keep it straight(er).

[ironhat]

After the last 3/4" sheet warped too severly to use I flung it on the burn pile out of spite. Now, if I need a little ply I buy a little ply. I paying more for it but not in another. I threw away 3/4 of that 3/4" piece so where was the servings there? I don't get much shop time these days and may never need that thickness again.

[Cochese]

I'm not one to thread-jack, but the title seems to perfectly state my question.

I have a 12x12 shed, and can think of two ideas for storing cutoffs - over my head, on 2x4s bolted to the joists and studs, or vertical against a wall. It's a low ceiling, so the sheets would be oriented short side down.

Which one would be better?

[pelligrini]

I put my sheet goods vertically against a wall, but I try to keep them as flat as possible. I have to be careful about not letting them fall back on me though.

I made an overhead rack in my garage for storing lumber and sheetgoods that fits between the door and the ceiling. It was a great use of unused space and it freed up a bunch of wallspace. It is a pain to access though. More often than not, the piece I need is at the bottom of the stack. Another thing I don't like about the overhead storage is that long items can be difficult.

In my shed I've got some overhead storage for lumber cutoffs. It's about 24" deep and fits right above the doors in the gable roof space.

[Larryl]

Erik - wow, you are definitely utilizing your space well. Nice clamp racks.