canoraf5199 Posted May 3, 2011 Report Share Posted May 3, 2011 I just built a standard weightlifting platform which consists of (4) 4x8 3/4" pieces of plywood criss crossed to form an 8x8 surface and screwed in using 2" and 1 5/8" drywall screws. problem is when someone walks on the platform it sinks slightly. these platforms are not supposed to have any give. I suspect 2 things. 1. the plans called for CDX plywood, but when I asked for it at home depot I was directed to and bought RTD sheathing. Is there a big difference between the 2 plywoods? 2. the platform lays on top of 1/2" rubber tiles which cover porcelain tiles. these rubber tiles are very solid gym flooring, not the foamy/spongy ones you sometimes see. But could it be that this is causing the sinking? Any help would be appreciated. Quote Link to comment Share on other sites More sharing options...
rmason Posted May 3, 2011 Report Share Posted May 3, 2011 My first thought is the 2" dry wall screws are 1/2" longer than 2 sheets of 3/4" plywood. Are they causing the plywood to not make full contact w/ the underlying surface? Second if the underlying floor is not perfectly flat the 8'x8' platform is going to span any hollows in the underlying floor and create the "give" you are trying to avoid. I would not think that the type of plywood would make a difference. Quote Link to comment Share on other sites More sharing options...
joestyles Posted May 3, 2011 Report Share Posted May 3, 2011 I agree with RedOak. Quote Link to comment Share on other sites More sharing options...
canoraf5199 Posted May 3, 2011 Author Report Share Posted May 3, 2011 My first thought is the 2" dry wall screws are 1/2" longer than 2 sheets of 3/4" plywood. Are they causing the plywood to not make full contact w/ the underlying surface? Second if the underlying floor is not perfectly flat the 8'x8' platform is going to span any hollows in the underlying floor and create the "give" you are trying to avoid the 2" screws were used for the top layer only which was another 1/2" plywood and 1/2" rubber mats on each side. 1 5/8" screws were used for the understructure. The floor seems reasonably level, never noticed any uneveness before. could it be the grout between the porcelain tiles? Quote Link to comment Share on other sites More sharing options...
canoraf5199 Posted May 4, 2011 Author Report Share Posted May 4, 2011 ok, I unscrewed the entire platform and it appears the problem is bowed plywood. Any thoughts on how to deal with this? Quote Link to comment Share on other sites More sharing options...
joestyles Posted May 5, 2011 Report Share Posted May 5, 2011 If it is all bowed the same way just reverse the pieces so that the bows oppose each other. The other option is new sheets. Question is why is it bowed? Was it like that before construction or after? Just shooting out some ideas and some considerations. Quote Link to comment Share on other sites More sharing options...
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