hi,

I'm redoing my floor in the basement. Basically on the concrete slab we put a .006 vapor barrier and then the 2x3 on which will be installed 2 layers of 5/8" plywood. The slab is not leveled so basically all the 2x3's are on shingles/shims. We're using tapcon screws through the 2x3 and the shingle into the concrete.

QUESTION: every how many inches/feet are we supposed to support the 2x3 with a shingle and a screw?

(the 2x3 are spaced every 16 inches and on top there will be 2 layers of 5/8 plywood placed "perpendicular" to each other)

thanks in advance

greg