Floor tile defects in Australian residential builds

What it is

A tiled floor on an Australian residential build has to comply with AS 3958.1, Ceramic tiles Part 1: Guide to the installation of ceramic tiles. The standard covers substrate preparation, adhesive selection, bedding methods, falls in wet areas, movement joints and grouting. Where the work follows the standard, a tile floor will last as long as the substrate beneath it. Where the work cuts corners, the defects show up in the first year as hollow tiles, lippage between adjacent tiles, cracked tiles over slab joints and grout that fails along high-traffic lines.

Substrate and bedding

The substrate has to be flat, dry, sound and free of contaminants before tiling starts. On a concrete slab the curing period is part of the substrate check. AS 3958.1 calls for the slab to be at least six weeks old before solid-bed tiling and longer for thicker pours. A slab that is still drying out shrinks under the tile and pulls the bed apart.

Adhesive selection is matched to the tile type and the location. Porcelain tiles need a high-polymer adhesive because the body is so dense the cement-based glue cannot key into it. Stone tiles need a rapid-set white adhesive to stop staining through the body of the tile. Wet area floors take a deformable (S1 or S2 classified) adhesive to handle the daily wet and dry cycle.

Hollow tiles

The most common defect raised on a tiled floor is the hollow tile. Tap a coin or a small metal probe across the floor and a tile bedded on less than full coverage will sound hollow rather than solid. AS 3958.1 requires at least 90 percent coverage in wet areas and at least 80 percent coverage in dry areas. Spot-bedded tiles (four blobs of adhesive in the corners) fail this test on day one.

Lippage and finish tolerance

Lippage is the height difference between adjacent tiles. AS 3958.1 sets tolerances that depend on the tile size and the joint width. The NSW Fair Trading Guide to standards and tolerances accepts up to 1 mm of lippage on tiles up to 200 mm wide and 2 mm on tiles wider than 200 mm. Anything above that gets called out as a defect.

Lippage comes from a substrate that is out of level, tile thickness variation between cartons that have not been mixed, or rushed levelling clip work where the spacers were knocked loose before the adhesive set.

Wet areas: falls and waterproofing

Wet area tile defects are the highest-cost category to rectify because they sit on top of the waterproofing membrane. AS 3958.1 and AS 3740 (waterproofing of domestic wet areas) work together. The standards require a fall to the floor waste of at least 1 in 80 over the whole shower floor with the rest of the bathroom floor falling generally toward the door or the waste so water does not pond against skirting tiles.

A defect in the falls (a flat shower floor, a hump near the waste) is rectifiable only by removing the tiles, the bed and sometimes the membrane. A bond breaker is required at every internal junction in a wet area so the membrane can move with the substrate without splitting. A missing bond breaker shows up later as a crack running along the floor-to-wall joint that lets water through.

Movement joints

AS 3958.1 requires expansion joints at room boundaries and at intervals of 4 to 6 metres across continuous tiled floors. Where tiling crosses an existing slab control joint, the joint has to be carried up through the tile. Where there is no joint, the tile floor is rigid and the slab below is not. The tiles crack in a line that follows the unseen movement.

Grout failure

Grout defects are often a symptom rather than a cause. Grout cracking along a single line points to a missing movement joint. Grout falling out across a whole area points to a wet grout mix or grouting before the adhesive had set. Grout going dark in patches points to moisture coming up through the bed.

Warranty and rectification

Floor tile defects fall inside the residential statutory warranties across Australia. In New South Wales the Home Building Act 1989 implies a warranty into every residential building contract. In Victoria the Domestic Building Contracts Act 1995 implies equivalent warranties. Major defects (water penetration through a tiled wet area floor) carry a six-year warranty period in most states. Minor defects (cosmetic lippage, isolated grout cracking) carry a two-year warranty.

Document floor tile defects with a tap test recording, a photograph showing the lippage against a straight edge and a moisture meter reading where damp is suspected.