Tile installation mistakes that cost money, and what each one costs to fix

Which shower do these numbers come from?

One case, stated once, so every dollar below can be checked. An alcove shower 60 by 32 inches, three walls tiled to 80 inches: 33.33 sq ft of back wall and 17.78 sq ft on each end wall, so 68.89 sq ft of wall, plus 13.33 sq ft of floor. Total 82.22 sq ft, in 12 by 24 inch porcelain with 1/8 inch joints. Labor runs at $41.31 an hour, the BLS mean wage for tile and stone setters in May 2025 ($28.49) times 46.65 divided by 32.17, the ratio of total compensation to wages in the June 2026 employer cost survey. Run your own square footage through the tile calculator first.

Why is water getting behind my shower tile?

This one costs the most because it fails slowly. Tile and cement grout both pass water, and USG is blunt about what its cement board does: it is a water-durable base for tub and shower areas, and the submittal sheet tells you to add a liquid membrane if waterproofing is what you want.

The second version is buying the membrane and applying too little of it. RedGard has two published rates: general waterproofing at 110 sq ft per gallon in each coat, and ANSI A118.10 at two coats of 80 sq ft per gallon each. Custom's coverage table shows what that buys. Combined 55 sq ft per gallon leaves 17 mils dry; combined 40 sq ft per gallon leaves 24 mils, the row flagged for A118.10. Seven mils is the whole difference, and nothing on the bucket tells you which one you just did. On 82.22 sq ft the A118.10 rate needs 2.06 gallons against 1.50, which in whole pails at $74.99 is three against two. Buy the third pail.

The 40 crew-hours and the two bags of mortar are my assumptions; the rest is priced from a source. The total leaves out the tile and the framing repair you find when a shower has leaked for years.

What backer board goes behind shower tile?

Read the substrate list on the bag instead of the forum thread. Custom lists gypsum wallboard as a substrate for VersaBond in interior dry areas, and lists drywall the same way for RedGard. USG sells Durock as the base for tub and shower areas. TCNA's shower answer is careful: its B421 and B422 methods put a membrane over solid backing, some membrane makers promote drywall as that backing and others do not, and the code language gets read both ways. So the usable rule is narrow. If your membrane manufacturer names drywall in writing for your method, it is allowed; if not, the repair is the $2,059.28 above. Six sheets of cement board cost $113.94.

Why does my tile sound hollow when I tap it?

ANSI A108.5 sets average mortar contact at no less than 80%, and at 95% on exterior and shower installations, verified by pulling no fewer than three tiles. The coverage has to be spread so corners and edges are supported, which is why a blob in the middle does not count.

Laticrete photographed what trowels actually deliver on an 18 by 18 inch tile: roughly 30 to 35% coverage from a 1/4 by 1/4 inch square notch, 55 to 60% from a 1/4 by 3/8 inch notch, and 75 to 80% from that same notch with the tile back-buttered. In a shower all three fail. The passing example is a 1/2 by 1/2 inch notch, mortar keyed into the substrate with the flat side first, tile back-buttered.

Put it in square feet. At 35% coverage, 28.8 sq ft of this shower is bonded and 53.4 sq ft is held by grout and friction. That is the hollow sound under the tap and the water path behind the wall. The correction is a $2.99 trowel and the habit of pulling a tile back up to look. Ace sells QEP's economy square-notch trowel, model 10120, for $2.99; the Ace listing gives the blade size and not the notch, so the 1/2 by 1/2 inch notch comes from QEP's own page for that model.

Back-buttering is the other half, and the same photos show why: coverage climbed 20 points with no change of trowel, because large tile is warped enough that the ridges never fully collapse. ANSI A108.5 spells out the 95% method, which is to back-butter each tile or pick a notch that gets you there, key the mortar in with the flat side, comb one direction, set perpendicular to the ridges.

Why did the bond fail when the mortar looked fine?

VersaBond takes 6 quarts of clean water per 50 lb bag. Slake it 5 to 10 minutes, stir again, do not add more water. Six quarts is 12.5 lb of water in 50 lb of powder, about 25% by weight; one extra quart is 2.1 lb, pushing it to 29%, a 17% increase. The data sheet lists 4-week shear bond on porcelain at 300 to 400 psi against an ANSI A118.4 floor of 200. Soupy mortar spends that margin.

Two clocks run at once. Pot life in the bucket is about 4 hours. Open time on the wall is more than 20 minutes by ANSI A118.4 section 5.3, a laboratory minimum rather than a promise on a hot day. If the combed mortar has skinned over and is no longer sticky, recomb it; if it has dried, scrape it off. Tile set into skinned mortar looks perfect and is bonded to nothing.

Grout is the last clock: VersaBond says 24 hours before grouting and light traffic, 7 to 10 days before heavy traffic, and Polyblend Plus wants the setting material cured 24 to 48 hours first.

Why does my grout keep cracking in the corners?

Tile expands, the wall behind it moves, and something has to give. TCNA detail EJ171 puts interior movement joints no more than 25 feet apart in both directions, and no more than 12 feet apart outdoors, in direct sunlight and above grade. Custom repeats the rule that matters on a small job: construction, expansion and isolation joints are never bridged with setting material. They come through the tile and get filled with sealant, Class 25 rather than Class 12-1/2 since the 2017 Handbook. In a shower the perimeter is the whole story: a soft joint at every change of plane, silicone instead of grout, because grout in an inside corner cracks and the crack is a water path.

Joint width decides the grout. Polyblend Plus sanded is an ANSI A118.7 product for joints 1/8 inch to 1/2 inch; the non-sanded version is ANSI A118.6, for joints up to 1/8 inch; the Handbook's minimum joint for any tile is 1/16 inch. Sanded is $25.99 for 25 lb, $1.04 a pound; non-sanded is $25.99 for 10 lb, $2.60. One 25 lb bag covers 461 sq ft of 12 by 24 inch tile at 1/8 inch joints, so this shower uses 18% of it. The wrong bag is a rounding error; the wrong joint means regrouting the shower.

Why did my floor tile crack down the middle?

Tile does not bend. VersaBond cites ANSI A108.01 Part 3.4: maximum allowable deflection L/360 for tile, L/720 for stone. Divide the span in inches by 360. A 12 foot joist span is 144 inches, so 0.40 inches is the ceiling and 0.20 for stone; a 16 foot span gives 0.53 and 0.27.

TCNA adds the caveat that keeps this honest. Its rigidity recommendations are empirical, drawn from what has worked in normal code construction rather than from deflection measurements, and failures have been seen on floors stiffer than L/360, down to L/600. On a springy floor, L/360 is the start of the conversation. Flatness is the other check, and a straightedge costs nothing. Count backer board with the drywall calculator.

Why did sealer leave a haze or blotchy grout?

Standards define porcelain as impervious, with water absorption of 0.5% or less by ASTM C373, so sealer has nowhere to go on it. What takes a penetrating sealer is cement grout, and Custom's data sheets treat that as optional protection against staining rather than waterproofing. Sealing the tile face leaves a haze to strip off; sealing instead of waterproofing leaves a shower with no membrane, the $2,059.28 line again. Polyblend Plus also asks for three days of misting and 72 hours at temperature to cure, and sealer over uncured grout blotches the color.

What does each tile mistake cost to fix?

The reset line is 24 hours of setting labor at $41.31 plus $41.98 of mortar; the regrout line is 8 hours of raking out joints plus a $25.99 bag. Every repair costs more than the fix that prevents it, and most cost ten times more. To price the whole job instead, the bathroom remodel guide puts waterproofing and tile in sequence with the inspections.