Bathroom Tiles Cracking Or Falling Off

What's happening?

Tiles do not fail on their own. They fail because of what is behind them or what is happening around them. A tile that comes off with clean adhesive on its back never bonded to the wall. A tile that comes off with plaster stuck to it has pulled the wall skin off, which means the plaster was too weak or too wet to be tiled. Cracks running in a straight line across several tiles are movement — a floor deflecting, a stud wall flexing, or a tiled area with nowhere to expand. Hollow-sounding tiles mean voids in the adhesive bed, common where tiles were fixed on dabs rather than a full, combed bed. In a bathroom the consequence is not only cosmetic: once a tile lifts, the joint opens and water gets behind the rest of them.

What usually causes it?

• Tiles fixed onto damp, dusty or unprimed plaster, or onto old gloss paint, so the adhesive never bonded
• Spot fixing on dabs instead of a full combed bed, leaving voids that fill with water and hold no strength
• The wrong adhesive for the tile or the background — ordinary adhesive under heavy porcelain, or non-flexible adhesive on a stud wall
• No movement joints across a large tiled area or where the tiling changes plane, so thermal movement has nowhere to go
• A flexing timber floor or stud partition beneath the tiling, cracking tiles in a line along the deflection
• Water getting behind the tiles from a failed seal, softening the plasterboard until it lets go
• Plasterboard used in a shower area instead of a tile backer board, so it swells once it gets wet

When should you call a bathroom fitter?

Call a bathroom fitter if more than a small patch sounds hollow, if the board behind a removed tile is soft or dark, if cracks run through the tiles rather than along the joints, or if any tiling in a shower has come away. A crack through the tiles is movement in the structure, and it will simply reappear in the new tiles unless the substrate and the joints are corrected first.

What will the bathroom fitter actually do?

• Sound the whole tiled area to map which tiles are bonded and which are hollow, and check the background behind a removed tile
• Establish the cause — background, adhesive, movement or water — before quoting a repair or a strip-out
• Strip failed tiling back to a sound substrate, replacing wet or crumbling plasterboard with tile backer board in wet zones
• Prime and, in shower areas, tank the background before fixing anything back
• Re-fix with an adhesive rated for the tile weight and the background, on a full combed bed with correct coverage
• Form movement joints at perimeters and changes of plane in flexible sealant rather than grout, then grout and seal the rest

Read the back of the tile that fell

• Clean adhesive on the tile, bare wall behind: the adhesive never bonded to the background.
• Plaster stuck to the adhesive: the wall skin failed, so the background was too weak or too wet to tile.
• Adhesive only in patches: it was spot fixed, and the rest was air.
• Dark, soft or crumbling board behind: water has been getting in, and the leak comes first.