Tile Over Wood Subfloor Bathroom

According to backer board manufacturers and tile setters installing backer board directly over an old solid wood subfloor is risky for a couple of reasons.

Tile over wood subfloor bathroom.

If the tile is being installed in a bathroom consider applying an isolation membrane over your wood subfloor to further protect against expansion and contraction. If water seeps through the tile installation to the underlayment it will not cause the wood to swell as happens with interior grade plywood. The old fashioned mud method of floating a thick mortar bed in preparation for the tile has given way to using cement backer board over a plywood subfloor. Installing tile over a wood subfloor is a lot easier today than it was when i started my remodeling career.

An uncoupling membrane does exactly what the name says. Generally this only refers to a layer of plywood but in the case of bathrooms it includes an underlayment of concrete backerboard as well. If installing over an appropriate wood surface sand the wood to make it smoother and remember that the installation will work better over a subfloor at least 1 1 8 inches thick. Don t lay tiles on a concrete slab with cracks that appear to be spreading or irregularities that prevent you from leveling it.

In addition uncoupling tile membranes prevent moisture from infiltrating surfaces below. Tape over holes and cracks in the wood subfloor or slab before pouring on the self leveling tile underlayment to keep it from seeping through and leaving indentations. Second the strength of wood boards isn t always consistent. The subfloor must be free of moisture damage including rot and sponginess and must be securely fastened to the joists and squeak free.

It uncouples or releases the bond between plywood and tile mortar allowing each surface to move independently of each other. First changes in humidity make solid wood shrink swell and cup more than plywood. Preparing a subfloor is an essential step for installing floor tile it provides a level surface that will allow the tiles to properly stay in place. Even if you use a waterproof underlayment membrane the floor will still be either 1 4 or 1 2 higher than the subfloor plus the thickness of the tile and adhesive.

While i prefer using 1 2 cement backer board over a plywood subfloor you may be able to get by with 1 4 backer board instead. When used as an underlayment the plywood sheets are laid over the osb or plywood subfloor for a two layer base.