Bathroom Tiling in London

Substrate, setting out and movement

Most tiling problems are substrate problems. Tiles need a background that is flat, sound, dry and stable, and almost every failure - cracked joints, hollow tiles, lifting edges - traces back to one of those four being absent rather than to the tiling itself.

Flatness matters more as tile size increases. A small tile with a grout line forgives a wall that undulates; a large-format tile bridges the high points and sits hollow over the low ones. Walls are therefore made flat before setting out rather than corrected in adhesive bed, which is a repair that fails under any real load.

Movement is the second issue, and in London conversions it is the common one. Timber floors deflect, and large tiles and stone do not tolerate deflection, so the floor is checked and stiffened or overboarded before anything is laid. Existing movement joints and changes of substrate are carried through the tiling rather than covered, because anything taken straight across them will crack along that line.

Setting out is what separates tiling that looks deliberate from tiling that looks fitted. The grid is planned so cuts fall where they are least visible, courses align with niches and shower screens, and the drain sits in a sensible relationship to the joints. That is decided on paper before the first cut, and it is the reason tile choice has to be settled early.

In wet areas the tiling sits on a tanked substrate rather than acting as the waterproofing itself. Grout and tile are not a membrane, and treating them as one is why splash zones that were never tanked come back as damp a year or two later.

Common questions

Can you tile over existing tiles?

Sometimes. Existing tiling that is firmly bonded, flat and free of movement can be worked over with the correct primer and adhesive, which avoids the mess and making-good of removal. Tiling that sounds hollow when tapped, or is lifting at the edges, has to come off, because anything laid over it inherits that failure.

Do timber floors need work before large-format tiles?

Usually yes. Boards flex and move seasonally, and large tiles and stone crack along the joints when the floor beneath them deflects. The floor is stiffened or overboarded and the joints treated before anything is laid, which is far cheaper than lifting a finished floor later.

Why does grout crack in the same place repeatedly?

Because that line is a movement joint rather than a grout line. Junctions between different substrates, at internal corners, and where a floor meets a wall all move independently, and rigid grout taken across them will keep failing. Those positions need a flexible joint formed properly rather than being re-grouted.