[BSponz1]

Hi – I’d like your opinions on what thickness of OSB I should use for a subfloor and whether the OSB should be T&G or butt-end. My plan is to use a product similar to Platon, DeltaFL, or Superseal and then install the OSB on top (duh) fastened with tapcons. Platon’s installation instructions, for instance, require a minimum of 7/16 OSB, either butt end or T&G. However, I’m concerned that 7/16 is too flimsy, and that butt end may not provide enough rigidity (I couldn’t find 7/16 T&G).

Aside from the head room savings between 7/16 and ¾ (half an inch is half an inch!), there’s also about a 7-8 dollar per sheet differentiation between 7/16 butt and ¾ T&G. Thoughts?

I plan to finish it with an engineered floor. The slab is relatively level with no obvious abnormalities, although once I get it cleaned out I’m going to hit it with a level everywhere I can.

 

[northernlite]

i just did something similar. i used 5/8 t&G OSB (it's actually labeled 19/32) and biscuit joined the butt ends. i had glued 1/2 styrofoam on the underside of the OSB before i put it down, then laid this over Superseal, then tapconned it down. worked great. i don't think i'd want to use less than 5/8", and certainly the t&g is a must in my mind.
i'd suggest getting or renting an sds drill, worth it for sure.