When we get called out to a cracked tile floor, the tile is almost never at fault. Porcelain is stronger than the concrete in your basement. The failure is underneath it.
The four causes
1. Deflection. The floor flexes underfoot. Tile is rigid and cannot flex with it. Industry standard is L/360 for ceramic and L/720 for natural stone — meaning across a 12-foot span the floor should deflect no more than 2/5 of an inch under load. Bouncy floors must be stiffened before tile.
2. No uncoupling membrane. Seasonal subfloor movement transmits straight into the tile. Cracks tend to run in a straight line across multiple tiles.
3. Poor mortar coverage. Voids under the tile leave it unsupported. Point load — a dropped pan, a chair leg — cracks it. This is what back-buttering prevents.
4. Movement joints omitted. Large tiled areas need soft joints at the perimeter and at intervals across the field. Without somewhere to expand, tile tents or cracks.
What proper preparation looks like
- Assess the subfloor. Walk it, feel for movement, check span and joist spacing.
- Check for moisture, particularly on slabs and in basements.
- Stiffen if needed — additional plywood layer, or blocking between joists.
- Level. Self-levelling compound where the floor is out. Non-negotiable for large format.
- Membrane. Uncoupling over plywood, waterproofing in wet areas.
- Set the tile with full coverage and levelling clips.
Roughly half the job
On most floors we quote, preparation is close to half the labour. It is invisible when finished, which is exactly why it is the first thing cut from a cheap quote — and exactly why that quote costs more in the end.
Can cracked tile be repaired?
Individual tiles can be cut out and replaced, but only if the underlying cause has been fixed. Replacing a cracked tile over a floor that still moves just buys you a few months. And dye lots change, so a replacement from new stock rarely matches — which is why we always tell clients to keep their offcuts.
Get a free estimate
Ultra Renovations Inc has been installing tile across Ajax, Pickering, Whitby, Oshawa and the wider GTA for over ten years. We are a registered Ontario corporation, fully insured, and rated 5.0 on Google.
Call (647) 648-8985 or request a free estimate and we will come out, measure properly, look at your subfloor, and give you a written quote for your floors at no cost.