Hollow tiles are not a tile problem. They are a bedding problem, and almost always one of six causes. Every one of them is preventable at no extra material cost.
1. Spot fixing instead of a full bed
Five dabs of adhesive at the corners and one in the middle is fast, and it leaves 60% of the tile back unsupported. Under a point load — a dropped weight, a trolley wheel, a table leg — the tile cracks at the void. Comb a full bed, every time.
2. Working past the open time
Combed adhesive stays able to wet the tile back for 30–35 minutes. In Guwahati's summer, with wind across an open floor, that shortens. Once a skin forms, the tile sits on the ridges instead of bedding into them. Press a finger into the bed: if nothing transfers to your finger, scrape it off and re-comb.
3. The wrong grade for the tile
A basic adhesive under a 800×1600 mm porcelain slab will fail eventually. Low-absorption, large and heavy materials need high polymer content and flexibility.
4. Soaking vitrified tiles
Soaking is a habit carried over from cement-sand mortar days. A vitrified tile cannot absorb water, so soaking only leaves a film of water between the adhesive and the tile. Fix tiles dry and clean.
5. Site additions
Cement added "to make it stronger", sand added to stretch the bag, extra water to make it easier to spread — each one changes the blend the product was tested at. This is the most common cause of a bag performing nothing like the datasheet.
6. No movement joints
Tiles expand and contract. A large floor laid wall to wall with no perimeter gap and no movement joints has nowhere to go, so it tents or debonds. Leave a perimeter gap under the skirting, and put in movement joints on large floors and where the substrate changes.
The ten-point check before you start
- Substrate clean, sound, dust free and cured for at least 28 days
- Flatness checked with a 2 m straightedge; dips levelled first
- Highly absorbent surfaces primed, excessively dry surfaces dampened
- Correct grade chosen for the tile size, material and location
- Clean water, correct ratio, mechanical mixer, five-minute standing time
- Correct notch size for the tile
- Only as much area combed as the team can tile within the open time
- Back-buttering on anything above 600×600 mm
- Tiles pressed and twisted into place, spacers used for uniform joints
- Perimeter gaps and movement joints planned before the first tile goes down
Testing the finished floor
Once the floor has cured, tap every tile with a coin or a small rod. A sharp, solid sound means a full bed; a dull drum means a void. Doing this at handover, when the tile can still be lifted and relaid cheaply, is far better than hearing about it from the client a year later.
Read next
- Tile Adhesive vs Cement Mortar: Which Is Better for Fixing Tiles?
- Tile Adhesive Type 1, Type 2 and Type 3: What the Difference Actually Means
- Tile Adhesive Coverage: How Many Bags per 100 sq ft?
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