Tile Problems: 9 Common Faults and How to Fix Each

Tile problems are one of the most common jobs a tiler gets called out for, and the good news is that most of them are fixable without ripping the whole room out. Cracked grout, a tile that sounds hollow underfoot, black mould creeping along the silicone: each one has a clear cause, and once you understand what went wrong you can usually put it right or know when to hand it to a professional. This guide walks through nine of the faults we see most often on walls and floors, what causes each, and the fix that actually holds.

Cracked grout: why it happens and how to fix it

Cracked or crumbling grout is the fault people notice first. Cement-based grout is rigid and brittle, so it cannot absorb movement. When the tiled surface expands, contracts or flexes and there is nowhere for that movement to go, the grout takes the strain and cracks along the joints.

The usual culprits are a floor that flexes because the substrate was not rigid enough, missing movement joints, or grout mixed too wet so it cured weak. For a cosmetic crack, rake out the loose grout with a grout saw, brush the joint clean and re-grout with a good flexible grout. If the same joints keep cracking, the movement needs somewhere to go: the joint should be formed as a flexible movement joint in silicone, not filled with more rigid grout. The British Standard for tiling, BS 5385, treats movement joints as a design requirement at wall and floor perimeters and at intervals across larger floors, not an optional extra.

Loose or drummy tiles

Tap across a tiled floor and you will sometimes hear a hollow, drum-like note. That drummy sound means the tile has lost its bond with the adhesive underneath, usually because the bed was not fully filled, the adhesive was past its working time when the tile went down, or the surface was dusty when it was fixed.

If the tile is still sitting flat and the grout is intact, you can often fix it without lifting it. Drill a small hole through a grout joint, inject a low-viscosity bonding adhesive designed for the job, and weight the tile until it sets. Where several neighbouring tiles are loose, it is usually better to lift and re-bed them properly, because the problem tends to spread.

Tiles lifting or tenting off the floor

When floor tiles rise up and pop, sometimes with a loud crack, that is tenting. It happens when the whole tiled field is under compression and has no room to expand. Heat from underfloor heating or direct sun, moisture in a new screed, or a floor tiled tight to the walls with no perimeter gap all build up pressure until the tiles lift at the weakest line.

Tenting is not a cosmetic job. The affected tiles need lifting, the bed grinding back, and the floor relaying with a proper expansion gap at the perimeter and movement joints across the field. This is one to get a tiler to assess, because relaying without solving the movement will simply repeat the fault.

Cracked tiles

A single cracked tile is usually caused by an impact, a void under the tile, or movement in the substrate below. If it is a one-off from a dropped object, replacing that tile is straightforward: score and cut out the grout, break the tile out from the centre working outwards, scrape the bed flat, and bed a matching replacement. Always keep a few spare tiles from the original job for exactly this reason.

If tiles keep cracking in a line, the substrate is moving and the fix is structural, not cosmetic. A flexing timber floor may need overboarding or an uncoupling mat before it is retiled.

Mouldy or blackened silicone sealant

Black spots along the silicone where the bath, tray or worktop meets the tiles are mould growing in and on the sealant. Once it is established you cannot clean it out for good, because the mould has rooted into the silicone itself.

The lasting fix is to remove the old bead completely. Cut it away with a sharp blade and a silicone remover, clean and dry the joint thoroughly, then reseal with a quality mould-resistant sanitary silicone. A clean, dry joint and a neat, continuous bead are what make it last; rushing this step is why so many sealant lines fail within a year.

Discoloured, stained grout

Grout goes grey and grubby because it is slightly porous and picks up soap, grease and dirt, especially on floors and around basins. It rarely means anything is structurally wrong, it just looks tired.

Start with a stiff brush and a proper grout cleaner rather than bleach, which can weaken the grout over time. Where cleaning will not shift it, a grout pen or grout reviver recolours the joints, and a grout sealer applied afterwards helps keep new dirt out. If the grout is also crumbling, recolouring is a waste of effort: rake it out and re-grout instead.

Water leaking behind shower tiles

Damp patches on the far side of a shower wall, or a musty smell, often mean water is getting behind the tiles. Tiles and grout are not fully waterproof on their own, which is why a shower or wet area should be tanked with a waterproof membrane before tiling. Cracked grout, failed silicone or a gap around the shower valve all give water a route in.

Reseal any failed joints and silicone as a first step. If the leak continues, the waterproofing behind the tiles has failed, and that means stripping the tiles in the affected area, tanking properly, and retiling. It is disruptive, but ignoring a leak behind tiles leads to rot and far bigger bills.

Efflorescence and lippage

Two smaller faults round out the list. Efflorescence is the white, powdery bloom that appears on grout or stone, caused by salts carried to the surface as water moves through the substrate. Wipe it off dry, and if it keeps returning, trace and stop the source of moisture. Lippage is when one tile sits proud of its neighbour, leaving a lip you can feel with a foot or a mop. It comes from an uneven bed or large tiles fixed without a levelling system, and short of relaying the high tiles there is no neat retro-fix, which is why getting the bed flat first matters so much with large-format tiles.

When to fix it yourself and when to call a tiler

Cleaning grout, replacing silicone, recolouring joints and swapping a single cracked tile are all reasonable DIY jobs if you are careful and patient. Tenting floors, repeated cracking along a line, and leaks behind shower tiles are signs of a deeper problem with movement or waterproofing, and those are worth a professional eye before you spend money twice. If you are in Bromley or south east London and are not sure which category your problem falls into, the team at Bromley Tilers can take a look and tell you honestly whether it is a patch repair or a relay.

Frequently asked questions

Why does my grout keep cracking after I redo it?

Because the underlying movement has not been dealt with. If the floor flexes or there are no movement joints, fresh rigid grout will crack in the same places. The joints that move need to be formed in flexible silicone, and a bouncy timber floor may need stiffening before it is retiled.

Can I fix a loose tile without taking it up?

Often yes. If the tile is flat and the grout is sound, drill through a grout joint, inject a suitable bonding adhesive, and weight the tile until it cures. If several tiles nearby are also loose, lifting and re-bedding them properly is the better long-term fix.

Is cracked grout a sign of a serious problem?

Not always. A single hairline crack is usually cosmetic. Cracking that follows a straight line across the floor, or that returns after every repair, points to substrate movement and is worth investigating properly.

How do I stop mould coming back on the silicone?

Remove the old sealant completely rather than cleaning it, make sure the joint is bone dry, and reseal with a mould-resistant sanitary silicone. Good ventilation and wiping down the shower after use slow regrowth considerably.

Do I need to reseal grout after cleaning it?

On floors and in wet areas it is a good idea. A grout sealer reduces how much dirt and moisture the grout absorbs, so it stays cleaner for longer and is less prone to staining.

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