Hollow Tiles Explained: Why They Matter

Run a coin across a freshly tiled floor and most tiles answer with a solid, dull “tock.” Then one replies with a hollow, drum-like ring. That single note is the most under-rated defect in a Singapore handover — cheap to fix on the developer’s dime now, expensive and disruptive to fix once you have moved in.

What “hollow” actually means

A tiled finish is a layered system — substrate, screed, adhesive bed, then tile — and BCA’s guidance is clear that it is only as strong as its weakest component. A hollow tile is one that has lost its bond to the layer beneath, leaving an air gap. Tap it and the void resonates; that drum sound is the gap talking.³

Why hollow tiles happen

It is almost always a workmanship shortcut upstream. BCA’s Good Industry Practices for ceramic tiling identify the usual culprits:²

• Incomplete adhesive coverage — the fix is to apply adhesive to both the substrate and the back of the tile (back-buttering) for full contact. Skip it and you bury voids under the tile.
• Lapsed “open time” — adhesive has a working window. Laying tiles after it has skinned over is a recognised cause of debonding and cracking.
• Uncured screed — BCA calls for the screed base to be air-cured for at least 7 days before floor tiles go down. Rush it and the moving substrate breaks the bond.
• Voids, an irregular subsurface, or separation of the waterproofing membrane beneath the bed.
²

Why they matter — it is not cosmetic

Owners often shrug off a hollow tile because it “looks fine.” The problem is what happens next. With no support beneath it, a hollow tile flexes under load and cracks; rows of them can pop or tent as the building moves and the void compresses; a lifted edge becomes a trip hazard; and in wet areas, the gap becomes a path for water to track sideways under the floor.

The standard: no hollow sound

You do not have to argue aesthetics. Under BCA’s CONQUAS — Singapore’s national construction-quality standard since 1989 — internal finishes including floor and wall tiling are assessed for hollowness, and the benchmark is that there should be no hollow sound when a tile is tapped with a tapping rod. That turns “I think this is dodgy” into “this fails the recognised workmanship standard.”^2,4

How to find hollow tiles yourself

1. Use a coin, key or light tapping rod and tap each tile near its centre and at each corner.
2. Listen for the change: a solid “tock” is bonded; a hollow “drum” is debonded.
3. Pay special attention to edges, doorways, and the perimeter of wet areas — failures start there.
4. Mark every hollow tile with masking tape and photograph it so your defect report is unambiguous.

Found hollow tiles at handover? Do this

For a new BTO flat, log them and report to HDB within 30 days of key collection, before renovation, under your 1-year Defects Liability Period — HDB rectifies genuine defects at no cost in that window. For a new condo or EC, report them in writing to the developer within your 12-month defects liability period and keep your dated, photographed list.⁵

Because hollow tiles are assessed against a published standard, they are one of the easier defects to get rectified — provided you catch them while the liability clock is still running. After it closes, the re-tiling bill is yours.