Hollow Tiles in a New Flat: Why They Sound Hollow and How They Get Fixed
How to run the tap test for hollow tiles, why tiles debond during laying, the IS 14687 threshold that decides re-laying versus a spot fix, and what each fix actually costs.
Updated · 6 min read · by HomeGyan certified engineers
The short answer
- Tap every tile with a coin or tap rod — a drummy, hollow sound means the bed under it never bonded, not just a cosmetic quirk.
- IS 14687 treats hollow area over 15% of a tiled surface as a defect requiring re-laying, not a touch-up.
- The fix depends entirely on timing: caught before grouting it is a same-day relay; found after handover it usually means a cut-and-relay, or a temporary epoxy injection.
- Epoxy grout injection buys time but doesn't recreate a full mortar bond — treat it as a stopgap, not a permanent repair.
- At a builder handover, hollow tiles are the builder's cost to fix under RERA's five-year defect liability, not yours.
How to run the tap test
Use a coin, a tap rod, or a small wooden mallet and tap across the tile in a grid, listening for a change in pitch. A solidly bonded tile gives a sharp, consistent sound; a debonded one sounds noticeably duller and hollow — the difference is obvious once you've heard both.
Do this room by room, including under furniture footprints and along walls, where hollowness is most often left unchecked because it's out of sight during a quick walkthrough.
Why tiles go hollow in the first place
- Dry, unsoaked tiles laid directly on cement — the tile absorbs water from the mortar bed before it can cure and bond properly.
- A thin or uneven mortar bed, often from rushed laying that skips full back-buttering of the tile.
- Wrong adhesive chosen for the tile type — porcelain and large-format tiles need a bonding agent that ordinary cement mortar cannot always provide.
- No compaction of the bedding layer, leaving air voids the tile simply sits over rather than bonds to.
- No allowance for movement over a large tiled area — without expansion joints, thermal movement eventually breaks the bond at the edges.
How much hollowness is actually acceptable
IS 14687 sets 15% hollow area on a given tiled surface as the threshold past which re-laying is required rather than a spot repair.
Treat wet areas — bathroom floors and dado in particular — with zero tolerance regardless of the percentage. A debonded tile there isn't just a durability issue; a hairline crack that follows can become a path for water straight into the waterproofing membrane and the slab below.
How a hollow tile is actually fixed
| Stage found | Fix method | How long it lasts |
|---|---|---|
| Before grouting | Lift the tile, clean the bed, re-lay with full mortar coverage | Permanent — the standard fix |
| After grouting, before handover | Cut out and re-lay the affected tile(s) individually | Permanent, though a later batch can leave a shade mismatch |
| After possession, small isolated area | Epoxy resin injected through the grout line to fill the void beneath | Temporary — several years typical, not indefinite |
| After possession, over ~15% of a room | Full re-lay of the affected floor or wall | Permanent |
Why epoxy injection isn't a permanent fix
Injected resin fills the void, but it doesn't recreate the compressive strength of a full mortar bed underneath. Under sustained foot traffic or heavy furniture, a fresh void can open up right next to the injected one.
It also isn't an option once the tile itself has already cracked — at that point the tile has to come out.
What it costs to get fixed
| Repair | Cost |
|---|---|
| Tile levelling / hollow tile fixing (epoxy injection, per job) | ₹3,000–₹12,000 |
| Floor tile replacement, supply + fix (per sq.ft) | ₹80–₹200 |
| Wall tile replacement (per sq.ft) | ₹90–₹220 |
| Re-grouting after tile replacement (per sq.ft) | ₹15–₹40 |
If you find this at a builder handover
Hollow tiling is a workmanship defect, and under RERA Section 14(3) the builder is obliged to rectify workmanship defects reported within five years of possession, at no cost to you.
Get it onto the snag list before you sign the possession letter — a defect recorded and dated in a pre-possession inspection carries far more weight than one raised verbally afterwards. Once repaired, re-inspect it: a re-lay is only confirmed fixed once it passes the tap test again, not once the builder says it's done.
Frequently asked questions
Can hollow tiles be fixed without removing them?
Only through epoxy resin injection through the grout line, and only where the tile itself hasn't already cracked. It is a temporary measure — expect it to last a few years rather than indefinitely, and it doesn't restore a full mortar bond.
What percentage of hollow tiles is acceptable in a new flat?
IS 14687 sets 15% hollow area on a given surface as the point at which re-laying is required. In wet areas such as bathroom floors and dado, treat any hollowness as worth fixing regardless of the percentage, given the added risk of water tracking through a cracked tile.
Do hollow tiles mean the floor is unsafe to walk on?
Not immediately — the risk is progressive, not sudden. A hollow tile is more likely to crack or detach over time under load, and in a wet area it can become a route for water into the slab below, which is why it's worth fixing rather than living with.
How is the tap test actually performed?
Tap the tile surface in a grid pattern with a coin, tap rod, or small wooden mallet and listen for a change from a sharp, solid sound to a duller, hollow one. Check under furniture footprints and along walls too — these are the spots most often skipped in a quick walkthrough.
Is the builder responsible for hollow tiles found after possession?
Yes, if it's within five years of possession. Hollow tiling is a workmanship defect under RERA Section 14(3), which obliges the builder to rectify it at no cost when reported within that window.
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