Ok, here goes…
I’m building a house in a cold winter area. The second floor is basically a rectangle 22’x45′, is the primary living area, and will have hydronic floor radiant heat. Below it will be half living space and half an attached, grade level, garage. The half living space on this first floor will have an open ceiling of timber joists and the second floor sub-loor underside visible. We plan to paint or stain this first floor exposed ceiling.
The entire second floor will consist of subflooring, inch and 1/2 gypsum concrete surrounding radiant heat tubing and 2×4 sleepers on the flat with hardwood flooring then on top.
My dilemma is what combination of second floor subflooring to use underneath this gypsum concrete; knowing that the underside will need to aesthetic for the exposure in the first floor ceiling and at the same time keep a constant thickness (or as close as possible) overall.
My initial thought is 3/4″ T&G sturdi floor (OSB or plywood) over the garage area and then over the first floor living space a combination of 1/4″ AC plywood (sand side down) followed by 1/2′ plywood on top to achieve the same overall second floor subfloor thickness. I’m concerned though of not having the benefit of T&G connectivity in this part of the subfloor.
Any comments, thought or advice is welcome – thank you