installing a subfloor over unlevel concrete

Old 08-03-04, 03:45 PM
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installing a subfloor over unlevel concrete

Thank you in advance for your assistance

I will be building a 12' x 12' piano room in a part of my garage. At one time the garage was a carport and the concrete floor was sloped intentionally to accomodate water drainage. The floor slopes 1.75" over the 12' length and needs to be leveled. I am looking for a cost effective resolution.

I was told that I could use 2x4s on the flat and shim them to correct the level, then install plywood over them. If this is the resolution, how often would I need to place shims, i.e. every 4'? Should I use presure treated 2x4s? Presure treated shims?

Alternatively I was considering framing the floor with 2x6s or 2X8s and shimming/supporting only the low end. Head room isn't that big of a concern as I have around an 8.5' ceiling.
Old 08-03-04, 07:48 PM
Join Date: Aug 2004
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First of all, if you are required to have covered off-street parking and this garage satisfies that requirement, you may face some liability.

However, what you've proposed, 2x4 wpt placed at a max. of 24"OC., shimmed with (2) cedar shims, glued, opposing, at 24" OC. covered with 3/4 OSB.

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