Am remodeling, and installing tile floor. Joists are 2x8 16 o.c., subfloor is 5/8 plywood perpendicular to joists, for underlayment should I use 3/8 plywood+1/2 in. backerboard or 5/8 ply+1/4 in. b-board? (also, should underlayment be laid same direction as subfloor? (with offset seams) thanks, Ray
When I did this in my old house I had a 3/4" subfloor and used 1/4" backer board (with 1/4" notch thinset between the subfloor and backer). I don't think that direction matters given how many fasteners you'll use on that backer board. Don't neglect to tape the joints either.
That floor never moved after adding tile on top.