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Tongue-and-groove OSB over 3/4″ foam problem

Tim Brown | Posted in Green Building Techniques on

I’m helping a friend with a basement remodel..
Winnipeg, Manitoba Canada zone 7.
1040 sq/ft basement, concrete walls and floor. no exterior insulation.

We are gluing (PL300) 2.5 inches EPS foam to interior walls. Then 2×4 walls (24″ o/c) with R14 Roxul, no poly then drywall). The wall foam is bonded to the floor foam with spray foam in a can. The corners and seams are all taped. The top will be foamed with a froth pack to seal against rim joists.

Laid 3/4″ foam to floors (is this supposed to be glued to the floor as well (PL300)?
The floor is not perfectly level but pretty good.
The 5/8 t&g OSB is the problem.

When laid on the floor the long sides (4×8 sheets) have t&g and lock together, the short sides don’t and are moving.

How do we prevent this movement on the short sides of the panels?

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  1. GBA Editor
    Martin Holladay | | #1

    You have two choices:

    1. Fasten the OSB subfloor to the concrete slab (through the rigid foam) with long TapCon fasteners.

    2. Use two layers of tongue-and-groove subflooring (either OSB or plywood), with staggered seams, and screw the two layers of subflooring to each other. This method prevents "potato chipping."

  2. Tim Brown | | #2

    Got it....thanks

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