Can I lay ceramic tile directly on a concrete floor? -Michelle
As long as the concrete slab is clean, flat, and free of active cracks, you can lay title directly on the concrete floor using thin-set adhesive.
Small cracks caused by shrinkage usually do not present a problem; but larger cracks, especially those that are higher on one side than the other, may telegraph through the tile and cause it to crack.
To find out if a concrete slab is clean, pour a little water on it in spots. If the water soaks in, you’re good to go. If the water beads up, it may indicate the presence of oil or wax which may cause adhesion problems with the thin-set.
To remove the oil or wax, clean the floor with a solution of TSP (trisodium phosphate) and water using a scrub brush or stiff broom. Rinse the floor with clean water to remove any residue, allow it to dry, then test it with water again.
Fill in any low spots on the slab with a self-leveling floor patch compound. Follow the directions on the container, and allow the compound to dry the recommended time before proceeding.
Good luck with your project,