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.
Proper subfloor for ceramic tile.
Tile floors are heavy and tile is a hard material.
Concrete expands and contracts and that type of movement can also crack the tiles and the grout.
It sounds like your joists are well within the acceptable limits of l 300 so your main concern is the deflection of the subfloor between joists.
Proper preparation of the subfloor is critical to the success of your ceramic tile installation.
This guide will show you how to prepare your subfloor for a tile installation project to ensure that it s fit to support ceramic or porcelain tile.
With ceramic tile you also need to limit the deflection between joists which is a function of the subfloor thickness and how it is installed.
For this reason ceramic and porcelain tile floors can be considered somewhat delicate despite the inherent strength of the material.
When installing a ceramic tile floor on a concrete subfloor you don t have to worry about flexing as long as the concrete slab is at least 1 1 8 inch thick which most slabs are.
A plywood subfloor must be structurally sound and able to support the installation.
Because of issues of moisture movement and adhesion ceramic tile will work well with certain types of subfloor underlayment systems and can go dramatically wrong with other subfloor materials.
However you re not out of the woods.
It will break or dislodge if the surface bends under the load.