Thinset Over Painted Floor

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

Thinset over painted floor.

First a surface more textured and solid must be applied over the painted concrete. The polymer modified thin set mortars might bond to a latex paint but not an oil based paint. Paint used on concrete will not bond with the tile adhesive. It cannot cure too fast.

This surface is called a scratch coat. Whether you have cracks chips or just a stained concrete slab thinset helps cover the old surface and create a new problem free area. Unfortunately the tile cannot be adhered directly to the painted surface. It must be easy to work with and it must adequately fill in gaps between the tile and the substrate.

Tile will stick to most rigid level surfaces including painted wood provided the correct preparation work is done to ensure the adhesive or mortar will stick to the floor surface. The floor is a 4 inch poured concrete slab over an unheated utility room. Otherwise you do. Mortar cannot be installed directly over painted concrete itself.

Mapei ultrafor plus data sheet says to use their keraply latex admix in lieu of water when going over impervious surfaces. A scratch coat will give the mortar something to hold on to instead of the layer of paint over concrete. All paint will need to be removed before you begin installing the tile. Whether wall or floor tile that tile needs to thoroughly stick to its base surface demands placed on tile adhesive are both extensive and steep.

The house was built in the late fifties and the slab floor has been painted at least once. Not that they would endorse going over an oil based paint what you should do is scarify the paint off the floor. Tile adhesive is expected to hold the tile in place not just for years but for decades without fail. Cracks and gaps can be filled with portland cement based fillers.