When a tile can be saved, and when it has to go

A loose tile that still moves underfoot but hasn't broken is the best possible candidate for a repair. If you can press it down and hear or feel it rock, the tile itself is usually sound — it's the adhesive bond underneath that has failed. That means you can often re-bond it in place and leave every surrounding tile untouched.

A single hairline crack in an otherwise stable tile is a greyer area. You can stabilise it and disguise it with a colour-matched two-part filler, but the crack will always be visible on close inspection. Cracks that radiate from a corner, or a tile that has broken into several pieces, usually means replacing the tile.

• Re-bond: tile intact, moves slightly, sounds hollow when tapped
• Repair and disguise: one fine crack, both halves sitting flush and level
• Replace: tile broken into pieces, multiple cracks, or crumbling edges
• Stop and investigate: three or more loose tiles in one area — that's a floor problem, not a tile problem

Work out why it failed before you start

Repairing a tile over a floor that is still moving just buys you a few months. Have a quick think about the cause first. The most common culprits in UK homes are spot-bonding (blobs of adhesive rather than a full bed), a lack of priming on dusty screed, and deflection in suspended timber floors where chipboard or floorboards flex under the tile.

Missing movement joints around the perimeter are another frequent offender — tiles need a gap of around 5mm at the edges, hidden under skirting, so the floor can expand. If your repair is in a conservatory or a room with underfloor heating, thermal movement is likely in the mix too. Fix the reason if you can, then repair the tile.

What you'll need

• A grout rake or an oscillating multi-tool with a carbide blade
• Thin flexible scrapers and a suction cup or tile lifter
• 4mm tile drill bits and a plastic adhesive syringe or injector
• Rapid-set flexible tile adhesive, plus a two-part epoxy adhesive for injection
• Matching grout — flexible or epoxy-based in wet areas
• Spacers, low-tack masking tape, rubber mallet, straight edge, spirit level
• Safety glasses, ear defenders and a dust mask

Re-bonding a loose tile that's still in one piece

Start by raking out the grout around the tile to a depth of about 3mm. This does two things: it stops the grout cracking when the tile shifts, and it gives you an escape route for old dust. Vacuum the joint out properly — fine dust is the enemy of adhesive.

Now try to lift the whole tile. Slide a thin scraper into the joint and work your way around, tapping gently with a mallet as you go. Many loose tiles will pop up cleanly, and re-laying one whole tile gives the best finish by far.

If the tile refuses to budge, leave it in place and inject instead. Drill two or three 4mm holes through the face of the tile, positioned at least 40mm in from the edges, and keep the drill shallow — stop the moment you're through the tile body. Mix a pourable two-part epoxy adhesive and inject it through the holes until it starts to squeeze back out. Wipe the surface immediately, weigh the tile down with something heavy and leave it 24 hours.

On floors with underfloor heating, be especially careful. Check where the heating mat or cable runs before you drill, keep the bit short so it can't reach the mat, and test the circuit with a multimeter both before and after the repair. A resistance reading that's unchanged means you've got away with it.

Lifting and relaying a loose tile

Once the tile is out, scrape the old adhesive off the back and out of the recess. Soak stubborn residue with warm water first, and take care not to gouge the screed deeper than the original bed. Hoover the recess and prime it if the surface is dusty or porous.

Apply a full bed of rapid-set flexible adhesive with a 6mm notched trowel, then back-butter the tile as well. Press it down with a slight twisting motion rather than dropping it flat, which traps air. Use spacers to keep the joints even, and check level against the neighbouring tiles with a straight edge — a 1mm lip is noticeable in bare feet.

Wipe any adhesive off the tile face while it's still wet, tape the joints if the tile wants to creep, and leave it alone. Rapid-set adhesive is usually firm enough to grout in two to three hours, but check the bag.

Grouting, curing and a bit of aftercare

Grout with a colour that matches the existing joints, working it in diagonally and sponging off before it dries. In kitchens, bathrooms and hallways, a flexible or epoxy grout will hold up far better than a basic cementitious one.

• No foot traffic for at least 24 hours
• No wet cleaning for five to seven days while the grout cures
• With underfloor heating, wait a week, then bring the temperature up in small steps — roughly 5°C per day
• Keep any leftover tiles from the original batch; matching a discontinued tile later is far harder than it sounds

Done carefully, a single-tile repair is a couple of hours' work and saves you the mess and expense of lifting a whole floor. Take your time with the grout removal, keep the dust down, and the repaired tile will disappear into the pattern as if it had never moved.