Some friends of mine are renovating an old home and want to put a ceramic tile floor on top of a T&G pine floor. The boards are about 1″ thick and supported on joists about every 20″. I assume that putting the tiles directly on the pine is a no-no due to movement. What is the best material to put on top of the pine to support the tiles? They don’t want anything too thick because of floor heights in adjoining rooms. The tiles will be in a bathroom and kitchen. If the best material is plywood or OSB, how thick and should it be treated in some way against possible future water problems?
Thanks greatly for your help
Replies
You should check the size of the joists and the span length to make sure you have at least L/360 deflection ratio (L is the span length). That is minimum recommended for tile. You will also need plywood or OSB on top of the solid wood floor. I think the minimum recommended thickness is 5/8 in. And then CBU or Ditra. Ditra can be made waterproof if you tape the joints. Tile goes on top of that.
Definately beef up your floor joist scenario. If your lay out is really 20" oc maybe reduce it to 10" oc, if it's possible to get at the floor joist system. If you need to minimize the effects of a raised floor height , I was on a job where we short screwed and glued 38s cdx to the existing subfloor, run the sheets perpendicular to the joists to try and purchase a little more integrity. Then we stapled 18 ga. stucco netting to the top of the plywood. after that we skim coated the wire with thin set, compatable with plywood. then we set the tiles . still no problems after 5 years.
Like previously mentioned you need to check for L360 deflection. Johnbridge.com has the formula for checking it. I put 3/4inch ply wood and 1/2 inch backerboad down and then tile but you could use 1/4 inch backer.