Is a hollow-sounding tile always a defect?
Not always. BCA's Good Industry Practices guide on ceramic tiling notes that hollowness can come from air voids in the bedding or slab, from an irregular subsurface, or from a waterproofing membrane separating from the slab, which it describes as an acoustic effect rather than a bonding problem. Hollowness matters most when it is extensive, spreading, at edges and corners, accompanied by cracking or lifting, or on walls and façades where a tile can fall.
From the RRD Field Guide, checked against the sources cited in Popped, Hollow and Debonded Tiles in Singapore: Causes, Safety, Repair and Who Pays. General information, not advice for your project.
The fuller picture
Tiles pop or sound hollow when the bond between tile, adhesive and screed fails, usually from thermal movement without movement joints, poor adhesive coverage, an uncured substrate or age. Indoors, the unit owner generally pays after the developer's 12-month defects period. On façades, falling tiles are a public-safety risk handled through the MCST or owner and BCA's Periodic Façade Inspection.
More questions on this topic
- Why do floor tiles suddenly pop up with a loud crack?
- Who pays for popped tiles in my HDB flat?
- Who pays for popped tiles in a condominium unit?
- Can the developer refuse to fix popped tiles after the defects liability period?
- Are popped façade tiles covered by the Periodic Façade Inspection?
- Can hollow tiles be fixed without removing them?
- How do I stop new tiles from popping?