Plywood - Warping - Power-lifting Platform - Woodworking Talk - Woodworkers Forum
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post #1 of 12 Old 03-09-2020, 09:52 PM Thread Starter
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Plywood - Warping - Power-lifting Platform

I've been using this platform style for years and every so often I have to re-build it (or re-arrange it) to accommodate the warps that develop.

The platform is made with 5 pieces of plywood. Two laid down side by side, two laid down on top of the first 2 but perpendicular, then one piece in the center with horse stall mats on the sides. Towards the back of the rack I have a strip that is 3 pieces of plywood thick that is not relevant to my questions below.

The layers have warped to the point that the front of the platform is about 0.5'' off the ground.

So my questions are:
1.) What can I do when rebuilding this platform to prevent the bottom 4 layers from warping? (Type of plywood, coatings, techniques, etc)
2.) I'd like to keep the top board since my logo is on it. If this board is warped, how can I make it flat again?





Thank yall so much for any guidance!

JK29
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post #2 of 12 Old 03-09-2020, 10:09 PM
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How are you attaching the layers of plywood?
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post #3 of 12 Old 03-09-2020, 10:34 PM
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Quote:
Originally Posted by JK29 View Post
I've been using this platform style for years and every so often I have to re-build it (or re-arrange it) to accommodate the warps that develop.



The platform is made with 5 pieces of plywood. Two laid down side by side, two laid down on top of the first 2 but perpendicular, then one piece in the center with horse stall mats on the sides. Towards the back of the rack I have a strip that is 3 pieces of plywood thick that is not relevant to my questions below.



The layers have warped to the point that the front of the platform is about 0.5'' off the ground.



So my questions are:

1.) What can I do when rebuilding this platform to prevent the bottom 4 layers from warping? (Type of plywood, coatings, techniques, etc)

2.) I'd like to keep the top board since my logo is on it. If this board is warped, how can I make it flat again?











Thank yall so much for any guidance!



JK29


Iím not sure how to help but I love power lifting. I have deadlifts tomorrow 2 sets of 315 for 10 reps a set . Iím working towards the the big 500lbs


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post #4 of 12 Old 03-09-2020, 11:20 PM
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My guess is the problem is coming from below. I learned a long time ago to never set wood directly on concrete floors or the wood will warp.

You could try putting a vapor barrier under it to keep the wood from making contact with the floor. The thicker the better. Maybe roofing or flooring underlayment.

Maybe someone can come up with other options.
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post #5 of 12 Old 03-10-2020, 12:55 PM Thread Starter
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How are you attaching the layers of plywood?
Deck Screws Alone, thanks.

Quote:
Originally Posted by Terry Q View Post
My guess is the problem is coming from below. I learned a long time ago to never set wood directly on concrete floors or the wood will warp.

You could try putting a vapor barrier under it to keep the wood from making contact with the floor. The thicker the better. Maybe roofing or flooring underlayment.

Maybe someone can come up with other options.
I like that idea. Would plastic sheet work you think?

Would coating the plywood with a sealer work too? Or buying treated boards?
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post #6 of 12 Old 03-10-2020, 01:42 PM
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Go to a dealer that sells flooring and pick up some underlay that is made specifically for laying a floor on concrete.
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post #7 of 12 Old 03-10-2020, 01:58 PM
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Originally Posted by JK29 View Post
Deck Screws Alone, thanks.



I like that idea. Would plastic sheet work you think?

Would coating the plywood with a sealer work too? Or buying treated boards?
6mil poly sheeting will work.
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post #8 of 12 Old 03-10-2020, 04:04 PM
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Nice set up!!!

I agree with Terry Q the problem is coming from the concrete slab so you need a vapor barrier. Plastic sheet would be thin and I think you would eventually would wear holes in it over time. I would use two, maybe 3 layers of 30lb roofing felt or 3 or 4 layers 15lb laid in opposite directions. It would provide a little bit of cushion and grip for the ply. You could paint a sealer like Red Guard on the concrete in addition to the roofing felt if you want to but I think that would be way overkill. Be sure to seal/finish the plywood on all 6 sides.

I would also run some Tapcons right into the concrete unless this is something you pick up once in a while.
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post #9 of 12 Old 03-10-2020, 07:23 PM Thread Starter
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Thanks all for the suggestions!

Any tips on getting warped pieces of plywood flat again?
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post #10 of 12 Old 03-11-2020, 09:25 AM
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I would try leaning each sheet concave side against a wall for a several days or a couple weeks with the bottom edge raised off the floor at least an inch. They might straighten out enough to be usable when the moisture evens out in the wood.
I've been successful with this method after leaving a stack of ply in my truck sit in the sun a couple hours causing the top sheet to curl like a potato chip. I don't think you will be as successful because it has been occurring slowly over time but you have nothing to lose. Maybe it will straighten out enough that you can force it flat attaching it to the concrete when you put it back down.
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post #11 of 12 Old 03-11-2020, 09:39 AM
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It occured to me while replying above that the horse mats would make a much better base layer. I would still start with roofing felt but two layers of 15lb would be sufficient. Is there any reason that wouldn't workout?
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post #12 of 12 Old 03-12-2020, 07:55 PM
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Everyone hit the nail on the head. Wood warps because of uneven moisture. The concrete will pass moisture into the ply. Put down the best vapor barrier you can. To prevent uneven moisture gain treat each side the same. Ply is prone to warping and it is nearly impossible to seal the edges well. After the new vapor barrier I like the idea of Tapconing the ply to the floor.
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