How to Replace a Few Cracked Ceramic Tiles
Why this matters
A cracked tile is a small repair with a big way to fail: the hammer that breaks out the bad tile cracks the good one next to it, and three tiles becomes five, then a conversation about where the attic stock went. Trades crack tiles all the time, dropping an old water heater, walking a dishwasher out, setting a ladder foot down hard. Replacing them is not tile setting in the full sense. It is isolating the damaged tile from its neighbors before any force goes into it, then setting a new one flush into a bed you have prepared to the right depth.
Before you break anything
Ask why it cracked. A star-shaped crack from a point is impact, and the tile is the whole problem. A straight crack that continues through the grout into the next tile, or a line of cracked tiles across a room, is the floor moving underneath, and new tiles over the same movement crack again. Tap the tiles around the damage with the handle of a screwdriver: a hollow sound means a tile that has let go of its bed. Diagnose before you replace; see related: Loose Tile + Floor Movement Diagnosis Reference.
Check for heat under the floor. Electric radiant mats sit in the thinset directly under the tile. A floor thermostat on the wall, often with a sensor wire, is the tell. Breaking out tile over a heating cable can cut it, and a cut heating cable is an electrician and the mat maker's repair kit, not a tile swap. If there is a mat, turn its circuit off at the breaker and confirm the thermostat shows no power, then work with hand tools only, chiseling shallow, and stop the moment you see cable. The circuit goes back on only after the thinset and grout have cured for the time the mat maker states, and then the floor is checked to warm at the thermostat; a mat that does not heat, or a breaker or GFCI that trips, means the cable was damaged and the circuit stays off until it is repaired.
Check the age of the floor. Thinset is not the only thing tile was set in. Older floors may be set in an organic mastic, and some older adhesives and the resilient floor sometimes found under a tile floor may contain asbestos. In a floor installed before the mid-1980s, run The Legacy Material Check Before You Disturb a Finish before grinding or chiseling the bed.
Have the replacement in hand. Attic stock from the original job first. A store match second, compared dry and wet next to the floor in daylight, and checked for the same thickness with a caliper or a ruler on a cut edge. See related: Why New Material Does Not Match Old Material.
The removal, drawn
TILE FIELD, SEEN FROM ABOVE
+---------+-+---------+-+---------+
| | | | | |
| good | | good | | good |
| | | | | |
+---------+-+---------+-+---------+
+---------+ +=========+ +---------+
| | | \ . / | | |
| good | | \ . / | | good | (X) drill holes
| | | ..(X).. | | | and score lines
| | | / . \ | | | at center; chisel
| | | / . \ | | | from (X) out to
+---------+ +=========+ +---------+ the edges
+---------+-+---------+-+---------+
| | | | | |
+---------+-+---------+-+---------+
^ grout cut out to full depth on all four
sides of the target tile FIRST
The grout removal is what isolates the tile. With the grout gone, the target tile is a separate island, and force applied to it has nowhere to travel into a neighbor. Breaking from the center sends each fragment outward into open joint instead of edgewise against the next tile.
The steps
1. Cut the grout out of all four joints, full depth. Use a hand grout saw, or an oscillating multi-tool with a carbide grout blade. Go down to the setting bed and run the full length of every side. Reason: see the drawing; grout locks tiles to each other. If you skip it: the first chisel strike carries straight through the grout into the neighbor, and it cracks along the line nearest you. Hazard: grout and thinset contain crystalline silica, and cutting or grinding them releases the respirable fraction. On construction work 29 CFR 1926.1153 governs it. Use a tool shroud on a vacuum with a HEPA filter, or work the joint wet, wear eye protection, and wear a respirator under a written 29 CFR 1910.134 program where your exposure assessment calls for one. Hand sawing makes far less dust than a power tool and is often fast enough for a few tiles.
2. Weaken the center of the tile. Drill three or four holes near the center with a carbide tile bit at low speed, or score an X corner to corner with a carbide scoring tool. Reason: a crack started at the center runs outward; a crack started at an edge runs into the neighbor. Hazard: tile glaze shatters into sharp chips; eye protection, and gloves when you pick up fragments.
3. Break out from the center with the chisel held low. Use a cold chisel and a small hammer at a shallow angle, starting in the center and working out to the edges, lifting fragments rather than driving them down. Reason: a chisel held upright drives force down into the bed and sideways at the edges; held low, it peels the tile up. If you skip it: fragments near the edge get driven against the neighbor's edge and chip its glaze. If the tile is hollow-sounding, it may lift out in a few large pieces with almost no force.
4. Clean the setting bed to depth. Chisel and scrape old thinset down until a new tile with a fresh bed will sit flush: lay the new tile in the opening dry, with a straightedge across it to the neighbors, and keep removing until it sits slightly low with room for new thinset, typically about 1/8 in to 3/16 in. Vacuum. Hazard: the same silica controls as step 1 apply to the bed; this is where most of the dust is made.
5. Back-butter the tile and comb the floor. Mix thinset suited to the tile and substrate, as the bag states, and to the slake time on the bag. Comb thinset onto the opening with a notched trowel in straight lines, and skim a thin flat coat onto the back of the tile. Reason: in a repair the bed is uneven, and a back-buttered tile fills the low spots. The setting standard, ANSI A108.5, which applies where the contract or the tile maker invokes it, calls for 80 percent mortar coverage in dry interior areas and 95 percent in wet areas and exteriors. If you skip it: hollow spots under the new tile crack it under a point load, the same way the old one cracked.
6. Set it flush and centered. Press the tile down with a slight back-and-forth, set spacers or wedges in the joints so the gap matches the old joints, and check flush with a straightedge across the neighbors in both directions. On the first tile you set, lift it straight back up and look at the back: if the thinset has not transferred over most of it, re-comb and re-set. If you skip the check: a tile that sits a sixteenth proud is a toe-catcher and a lipped edge that chips.
7. Wait before grouting. Clean thinset out of the joints with a margin trowel while it is soft, then leave the tile alone for the cure the thinset bag states before grouting, commonly about a day. Reason: grouting a tile that can still move breaks its bond. Grout matching is its own procedure; see related: How to Match Grout Around Replaced Tile.
Worked example: three tiles at a water heater
A plumber's crew walks a 50-gallon water heater out of a laundry room on a dolly, and the dolly's toe drops hard on the tile floor at the threshold. Three tiles crack: two with star cracks from the toe and one with a crack from corner to center. The floor is 12 in ceramic with 1/8 in joints, set in thinset over a cement backer board; the house is from 2004, so outside the legacy window. No floor thermostat on any wall. The homeowner has six tiles of attic stock in the garage.
Diagnosis. All three cracks start from a point or a corner in the drop zone, none continue into the grout, and the tiles in the next row are not cracked. That is impact, not movement. The tap test finds one more tile, next to the corner-cracked one, that sounds hollow over about a third of its area but is not cracked.
The fork. A hollow tile is a tile whose bond has partly let go, and it is the next one to crack. Leaving it means the customer sees a crack in the same spot in six months and blames the repair. Replacing it means four tiles instead of three, and two attic-stock tiles left over instead of three. The plumber calls the homeowner, explains that the fourth tile tested hollow but is not damaged, and gets the go-ahead to replace four. Six tiles in stock, four used: two remain, and the ticket says so.
Removal. Grout cut out by hand around all four tiles. The two star-cracked tiles and the corner-cracked one came out from the center; the hollow tile lifted out in two large pieces, and its back showed thinset contact on only about half its area, which confirmed the call. Bed cleaned down until a dry tile sat about 1/8 in low under a straightedge.
Setting. Thinset combed and tiles back-buttered. The first tile set was lifted for a look and showed thinset transfer across most of its back. Spacers in all joints at 1/8 in, straightedge flush across all four in both directions. Joints cleaned out with a margin trowel. Grout left for the next day per the thinset bag.
Result. Four tiles replaced, all flush, all solid on a tap test the next morning before grout. The ticket records the cause of the damage, the hollow tile found and the customer's approval to replace it, the tile and thinset used, and the attic stock remaining.
How to verify
Before grouting: every new tile flush with its neighbors under a straightedge in both directions, solid on a tap test, joints even and clean to depth. After grouting: no cracked or chipped neighbor anywhere around the work, checked with the same tap test, because a neighbor cracked by the removal is cheaper to find now than in a callback.
References
- See related: Loose Tile + Floor Movement Diagnosis Reference
- See related: How to Match Grout Around Replaced Tile; Tile + Grout Selection Reference
- OSHA 29 CFR 1926.1153, respirable crystalline silica in construction; 29 CFR 1910.134, respiratory protection
- ANSI A108.5, setting of ceramic tile with dry-set or latex-portland cement mortar, current edition
- See related: The Legacy Material Check Before You Disturb a Finish