Subfloor for Garage Reno

[PaulF]

Good morning everyone. I am converting the small garage of my 1930s house into an office. Garage sits on 6 inch concrete slab, feels a little damp after rain. Planning to lay ceramic tile over a subfloor get some warmth and moisture protection. For subfloor, I bought Delta-FL product. Two questions:

1. Any experience using Delta-FL in this sort of application? Recommended?
2. What to put over the Delta-FL? OSB vs Wonderboard?

Thank you for your help!
--Paul

 

[Dana]

While I haven't used Delta-FL specifically, it's a well know standard product with a good reputation. It should work just fine.

Wonderboard is likely to have too much give at the seams. A single layer of 3/4" t & g subfloor would work, but even that could end up with some movement at the seams cracking the tiles unless you TapCon the panels to the slab on a 24" grid or tighter. A double layer of 1/2" OSB sheathing screwed & glued together into one monolithic subfloor would be more stable. If the slab is resonably flat it's fine to just float the subfloor rather than screwing it to the slab. But with any wood subfloor solution leave 3/8"-1/2" around the perimeter for seasonal dimensional changes from humidity.

Be sure to air seal the perimeter of the Delta-FL to avoid winter winds pushing under the floor creating cold spots.