Why do tiles come loose, and how do you fix them?

Insufficient adhesive coverage is by far the most common cause. If a tiler used the dot-and-dab method, applying a few blobs of adhesive rather than combing out a full solid bed, large voids are left behind each tile. Over time, particularly with the heat and moisture cycles of a bathroom, the tile can rock loose in these unsupported areas and eventually detach.

Tiling onto an unprimed or dusty surface is the second most common cause. Plaster, plasterboard and old adhesive all need to be clean, sound and, in the case of plaster, sealed with an appropriate primer before tiling. Adhesive cannot form a proper mechanical and chemical key to a dusty or powdery surface, so it lets go under normal thermal movement.

Tiling directly onto old paint, gloss or a painted surface is a common DIY mistake. Adhesive does not bond reliably to paint, and the paint film itself can peel away from the wall taking the tile with it.

Movement in the substrate, particularly at internal corners, around bath edges, or where a stud wall meets a solid wall, can crack the adhesive bond over time if no flexible movement joint was left. Timber floors and stud walls flex more than block or brick, so tiles fixed rigidly across a junction are more vulnerable.

Moisture getting in behind the tiles from failed grout or perished sealant softens some adhesives and can also cause plasterboard to lose its integrity, so tiles that were once sound come loose months or years later.

Using the wrong adhesive for the board is another cause. Standard cement-based adhesive is not always suitable for every tile backer board, and large or heavy porcelain tiles need a stronger, often flexible, adhesive than a light ceramic tile.

Tap each tile firmly with a knuckle or the handle of a screwdriver. A solid, dull thud means good adhesive contact. A hollow, ringing sound means a void behind that tile. Work across the whole wall and mark hollow tiles lightly with masking tape so you can see the pattern.

If hollow tiles are scattered randomly and are a small minority, individual re-fixing is usually enough. If most of the wall sounds hollow, or hollow tiles are concentrated low down or around the bath and shower area where moisture collects, this points to a wall-wide fixing or moisture problem rather than a couple of unlucky tiles.

Rake out the grout around the loose tile with a grout rake or a flathead screwdriver, taking care not to damage neighbouring tiles. Use a thin blade or an oscillating multi-tool to work behind the tile and lift it away, along with any old adhesive that is not firmly attached to the wall.

Clean the exposed area back to a sound, flat surface. If you have exposed bare plasterboard or plaster, apply a primer suited to the wall and let it dry fully.

Comb a full bed of adhesive onto the back of the tile with a notched trowel so the ridges run in one direction, then press the tile into place with a slight twist to collapse the ridges into a solid bed. Use tile spacers to keep the joint widths consistent with the surrounding tiles, and check the tile sits flush using a straight edge across neighbouring tiles.

Leave the adhesive to cure for the time stated on the packaging, usually 24 hours, before regrouting. Match the grout colour as closely as possible; slight variation is normal even with the same product from a different batch.

If hollow-sounding tiles are widespread, if you find damp or soft plasterboard behind removed tiles, or if tiles are coming away in multiple unconnected areas, patch repairs are a false economy. The safer and longer-lasting approach is to strip the wall back, replace any damaged board, and re-tile with correct adhesive coverage and, where needed, a tanking or waterproofing membrane in wet areas.

This is also the point to check for a movement joint at internal corners and where the wall meets the bath or shower tray, since these are flexible sealant joints rather than rigid grout joints for good reason.

For most bathroom wall tiles, a solid bed with close to full coverage on the back of the tile is what prevents future hollow spots and lets the tile properly resist moisture getting behind it. The table below gives typical notched trowel sizes used for different tile formats; larger and heavier tiles need a bigger notch to leave enough adhesive to fully bed the tile.

In a bathroom, moisture is the usual accelerant. Tiles around a bath rim or shower tray loosen first because water reaches the adhesive through a perished sealant line, so the repair has to include resealing that junction or the problem returns.

In a kitchen, heat behind a hob and the weight of large tiles on plasterboard matter more. The fix is the same principle: a clean, primed surface, the right adhesive for the tile weight and a full bed rather than dabs.