Thinset Over Painted Floor

Thinset mortar is your default tile mortar for most indoor and outdoor applications.

Thinset over painted floor.

This surface is called a scratch coat. The house was built in the late fifties and the slab floor has been painted at least once. Only use epoxy and latex thin set products that state they can be used for bonding tile to paint. 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. Unfortunately the tile cannot be adhered directly to the painted surface. The painted surface has to be cleaned properly to ensure an adequate bond. 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. Mortar cannot be installed directly over painted concrete itself. Installing tile over painted concrete adds a few extra steps to your tiling job. Thinset tile mortar has a smooth slippery consistency similar to mud.

Thinset is a mortar that is made of portland cement silica sand and moisture retaining agents. Apply a coat of sanding sealer or tile prep sealer to the floor with a paint roller. If the paint is not well attached then as the thin set adhesive dries and shrinks it might pull the paint loose. All paint will need to be removed before you begin installing the tile.

It is applied to the substrate with a notched trowel. A scratch coat will give the mortar something to hold on to instead of the layer of paint over concrete.