Tiling Over Existing Tiles

Tiling over existing tiles can be an option when the old tiles are firmly bonded to a sound wall or floor, the surface is flat, and there's room for the extra thickness. It's more often suitable on walls in dry areas than on floors or in showers.

Tap the old tiles: a hollow sound means there's a gap behind the tile and it isn't fully bonded. Loose, hollow or cracked tiles can't support a new layer and will usually fail, taking the new tiles with them. If more than a few are loose, it often points to a problem with the wall or floor behind, and the old tiles should come off.

Glazed tiles are smooth and don't absorb water, so new adhesive struggles to grip them. The old surface is cleaned to remove grease and soap, then primed with a primer made for tiling over tiles, or the glaze is roughened, following the manufacturer's instructions. Use an adhesive rated for tiling onto existing tiles.

Two layers of tiles weigh more than one. The wall and the original fixing have to carry both, so check the weight of the new tiles against what the wall can take, especially on plasterboard.

A second layer raises a floor and thickens a wall. On floors this can stop doors opening, leave a step at thresholds and affect the space under kitchen appliances and units. On walls it can leave sockets, switches, taps and window reveals sitting too deep, and exposed edges may need trims.

In a shower, tiling over tiles leaves whatever is behind the old tiles in place, and it can't be checked. If the shower was leaking, or the old tiles were never tanked, tiling over doesn't fix that. In wet areas the old tiles are usually removed so the walls can be boarded where needed and waterproofed before tiling.

Stripping out old tiles and adhesive takes the wall or floor back to a surface that can be checked and repaired. Robert strips out, prepares, waterproofs and tiles as part of the job, so the new tiles go onto a sound base rather than over a problem.