Thinset Over Painted Floor

A scratch coat will give the mortar something to hold on to instead of the layer of paint over concrete.

Thinset over painted floor.

It must be easy to work with and it must adequately fill in gaps between the tile and the substrate. Installing tile over painted concrete adds a few extra steps to your tiling job. Tile cannot be attached directly to painted concrete as the thin set will not adhere well to the paint. Paint used on concrete will not bond with the tile adhesive.

Cracks and gaps can be filled with portland cement based fillers. All paint will need to be removed before you begin installing the tile. Mapei ultrafor plus data sheet says to use their keraply latex admix in lieu of water when going over impervious surfaces. Whether you have cracks chips or just a stained concrete slab thinset helps cover the old surface and create a new problem free area.

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. It cannot cure too fast. Not that they would endorse going over an oil based paint what you should do is scarify the paint off the floor. The floor is a 4 inch poured concrete slab over an unheated utility room.

Otherwise you do. The safest way to approach questionable concrete is not to cover it over with cbus but to fix the concrete. The house was built in the late fifties and the slab floor has been painted at least once. The polymer modified thin set mortars might bond to a latex paint but not an oil based paint.

This surface is called a scratch coat. Unfortunately the tile cannot be adhered directly to the painted surface. First a surface more textured and solid must be applied over the painted concrete. Tile adhesive is expected to hold the tile in place not just for years but for decades without fail.