Thinset Over Painted Floor

Installing tile over painted concrete adds a few extra steps to your tiling job.

Thinset over painted floor.

The painted surface has to be cleaned properly to ensure an adequate bond. It is applied to the substrate with a notched trowel. All paint will need to be removed before you begin installing the tile. Unfortunately the tile cannot be adhered directly to the painted surface.

Only use epoxy and latex thin set products that state they can be used for bonding tile to paint. Thinset is a mortar that is made of portland cement silica sand and moisture retaining agents. Thinset tile mortar has a smooth slippery consistency similar to mud. The floor is a 4 inch poured concrete slab over an unheated utility room.

Paint used on concrete will not bond with the tile adhesive. The house was built in the late fifties and the slab floor has been painted at least once. Mortar cannot be installed directly over painted concrete itself. This surface is called a scratch coat.

The thin mix is laid over. A scratch coat will give the mortar something to hold on to instead of the layer of paint over concrete. A latex based thin set adhesive should be used over the latex based paint. First a surface more textured and solid must be applied over the painted concrete.

If the paint is not well attached then as the thin set adhesive dries and shrinks it might pull the paint loose. Apply a coat of sanding sealer or tile prep sealer to the floor with a paint roller.