Tile and Grout Repair Standard

Purpose

A cracked grout line is not a grout failure. It is a report from underneath, and it usually reports one of two things: the assembly is moving where nobody gave it a joint, or the tile was never bonded properly.

This procedure stops two losses: the regrout that comes back in one season because the crack was a movement joint the shop filled with cement, and a silica exposure from grinding grout dry in an occupied bathroom that cannot clear the dust.

Scope

Covers repair of existing ceramic, porcelain and quarry tile in residential and small commercial interiors: hollow tile diagnosis, grout removal and replacement, single tile and small group replacement, sealant at movement joints, and the repair-against-refer call.

Does not cover new installation over new substrate, shower pan or waterproofing work, stone restoration, or any assembly whose waterproofing has been breached; those go to a tile contractor. Sealant selection by joint width belongs to the caulk and backer rod article.

Roles and responsibilities

Procedure

1. Sound the whole field before you mix or cut anything. Tap every tile with a screwdriver handle and mark each one that answers hollow, not dead. Acceptance: a written map giving total tiles in the field, hollow tiles, and cracked joint length in feet. Two stop gates, either firing on its own: hollow tiles above about 10 percent of the field count, or a contiguous group of more than four, means the setting bed is the fault and the work is a field re-set. Wrong looks like: sounding only the reported tiles, so the next hollow one in the same bad bed reads as your workmanship. Hazard: none beyond kneeling, so use a pad and change position.

2. Separate a movement crack from a bond failure by where the crack runs. A crack following one continuous line across the field, over a joist, a slab joint or a change of substrate, is movement; cracks scattered at random tile corners are bond. Acceptance: every crack classified line or scatter, and every inside corner, tub-to-tile joint and floor-to-wall junction identified as a joint that should carry flexible sealant rather than cement grout. Wrong looks like: grouting an inside corner because the rest of the room is grouted, which cracks out within a season. Hazard: a cracked field holds loose and fractured tile, so kneel on a pad rather than on the tiles, keep bare hands off a broken edge, which cuts like glass, and pry nothing here. Stop rule: a line crack with no joint provided for it routes to the lead, because a movement joint has to be cut in, and the TCNA Handbook detail EJ171, in the edition current for that assembly, reaches you through the manufacturer warranty rather than through code.

3. Prove the floor does not move under load before you re-bed anything. Stand on each hollow tile and on the cracked line while a second person watches the joint. Acceptance: no visible joint movement, no click, no flex underfoot, and on a wood-framed floor a substrate meeting the deflection limit industry practice sets, commonly L/360 for ceramic and porcelain and L/720 for stone. Stop rule: any deflection, any click, or a span you cannot verify goes to the lead, because reinforcing framing is not handyman scope. Hazard: over a crawlspace, confirm nobody is underneath before you load-test, since a tile that lets go throws chips through an open joist bay.

4. Remove failed grout wet or with dust collection, never dry with a grinder. Use a carbide grout saw or an oscillating tool with a grout blade; a grinder only with a shroud and dust collection run to the manufacturer's instructions. Acceptance: joint cleaned to two thirds of tile thickness or to the setting bed, joint walls square, no chipped tile edges, doorway sealed with plastic before the first cut. Hazard matched to the route: grout and tile release respirable crystalline silica when cut or abraded, which is inhalation, so a glove and a face shield do not address it. Repair work is normally construction, putting it under 29 CFR 1926.1153, with 1910.1053 the general industry twin; the split follows the activity, not the building. Read Table 1's mortar-removal entry in the current text rather than from memory, and put any respirator under a written program per 29 CFR 1910.134; if nobody on the crew is in that program, the joint gets cut by hand wet instead, and dust seen leaving the work area stops the cut regardless: clear occupants and go to hand tools. Second route: wet cement is strongly alkaline and burns on prolonged skin contact, so gloves go on for the wet work too, and a slurry splash in an eye gets flushed at least 15 minutes plus a medical call, not a wipe.

5. Lift a hollow tile and read the coverage before deciding what the repair is. Remove one hollow tile from the middle of the group and estimate the percentage of its back carrying thinset. Acceptance: coverage written down as a percentage of the tile back, against the mortar coverage minimums the ANSI A108 series sets, 80 percent in dry interior areas and 95 percent in wet areas, exteriors and under stone, with full support at all four corners; those minimums reach you through the specification, not code. Wrong looks like: re-bedding hollow tiles into a field set at half coverage, which fixes six tiles and leaves the next six on their own schedule. Stop rule: coverage below the applicable minimum means the setting is the defect and the work is a re-set, so photograph the tile back against a tape and get authorization for the changed scope. Hazard: lifting a bonded tile fractures it and throws sharp shards, so wear eye protection and gloves, chisel from an open joint toward the tile center, not off a neighbor, and keep the customer and pets out of the room.

6. Re-bed and grout to the manufacturer's published mix, not by feel. Mix to the water ratio and slake time on the bag, then remix without adding water. Acceptance: replacement tiles level with the field within about 1/32 in lippage across the joint, grout packed full and struck flush to lightly concave, no voids at tile corners. Wrong looks like: soupy grout that shrinks below the tile edge as it cures, nearly always water added after slaking. Stop rule: grout setting faster than you can strike it is a batch problem, so dump it and mix smaller rather than working it wet. The hazard is in the mixing, not the tiling: dumping dry powder liberates silica and cement dust, so cut the bag low, pour powder into water rather than the reverse, and mix on slow speed.

7. Fill every change of plane with sealant and give the joint its cure. Backer rod where the joint is deep enough, then a sealant compatible with the grout color and the wet exposure. Acceptance: sealant tooled concave with continuous contact on both faces, consistent joint width, and the label cure time written on the ticket and told to the customer. Hazard: some sealants cure by releasing solvent or acetic acid vapour into a small unventilated bathroom, so ventilate to outdoors while tooling and curing rather than assuming a neutral cure. Stop rule: a joint too wide for a single bead, or one bridging a broken tile edge, is not a sealant repair, so replace the tile first.

8. Restore everything you shut off and verify before you leave. Acceptance: every fixture stop closed and every drain plugged during the repair recorded as restored, and water running and draining with no leak at the fixture you disturbed. Wrong looks like: a supply stop left closed under a vanity you moved, which the customer finds that night. Stop rule: any fixture that does not restore stays on the ticket as open work and the customer is told before you leave. Hazard: the first re-pressurisation of a closed stop is where an old packing nut weeps, so open it slowly with a rag and a hand on the valve and watch the stem for 30 seconds.

The record this produces

Field tile count, hollow count and arrangement, cracked joint length in feet, every crack classified line or scatter, the coverage percentage read off the lifted tile, grout and sealant products with color, the cure window given, and a restore line for every isolation made.

The office reads the coverage figure when the customer calls about a different tile six months later, because a field documented below the minimum has already had that conversation. The next tech reads the sounding map to know whether a new hollow tile is new or known. The owner reads coverage in aggregate: low coverage across houses from one builder is a scoping rule, not bad luck.

Worked pass: master bathroom floor, six hollow tiles and one cracked line

Complaint: grout cracked along one line at the vanity, and a few tiles sound loose.

Step 1: the floor is 8 ft by 12 ft with 12 in tiles, so 96 tiles in the field. Sounding found 6 hollow, all six together in a block in front of the vanity, and 11 ft of cracked joint. 6 of 96 is 6.25 percent, under the 10 percent gate, which passes; a contiguous group of six is more than four, so the second gate trips on its own and the map went to the lead before anything was cut. The gate's stated consequence is a field re-set, and the lead authorized carrying on to step 5 first rather than quoting one off the sounding map alone, because lifting a tile is what confirms whether the bed or the grout is the defect.

Step 2: the 11 ft crack runs in one straight line but across the tile field rather than along a joist direction, and the room carries no movement joint anywhere. Classified as line. The floor-to-wall and tub-to-tile joints were both filled with cement grout, and both were logged as joints that should have carried sealant.

Step 3: two people, one standing on each hollow tile in turn. No click, no visible joint movement, and framing was verifiable from the basement as 2x10 joists at 16 in centers over a measured span, clearing L/360 for porcelain. Nobody was under the floor during the test. Passed.

Step 5 FAILED, and it was taken ahead of step 4 deliberately, because lifting one tile reads the bed without cutting a joint, so scope is settled before any dust is made. The lifted tile carried thinset on roughly 35 percent of its back, all four corners bare, against the 95 percent minimum that applies to a bathroom floor as a wet area. Under the step's own stop rule that is the setting bed rather than the grout, so the tech stopped, photographed the tile back against a tape, and called the office rather than buttering six tiles back into a bad bed.

Scope changed on that call. The customer authorized re-setting the six-tile block and cutting a proper sealant joint at the wall junction, with a written note that further hollow tiles are expected at that coverage rather than warranted. The full field re-set was quoted as its own visit.

Steps 4, 6, 7 and 8 then ran on the reduced scope: joints cut by hand wet with a carbide saw rather than a grinder, because nobody on the truck was in a respirator program that day; six tiles re-bedded to full coverage; 11 ft of joint regrouted; the wall junction sealed over backer rod; the vanity stop reopened slowly and watched.

References

• The thinset, grout and sealant manufacturers' published mixing ratios, coverage requirements and cure times for the products in your hand
• ANSI A108 series and the TCNA Handbook, in the edition current for the assembly, which set the mortar coverage minimums and the movement joint detail EJ171
• 29 CFR 1926.1153 (construction) and 29 CFR 1910.1053 (general industry) on respirable crystalline silica, including Table 1's mortar-removal entry, with 29 CFR 1910.134, which conditions respirator use on a written program with medical evaluation and fit testing
• See related: Caulk vs Backer Rod vs Trim for Gap by Width and Movement; Grout Cracks Back Only Along One Line, Movement vs Mix