Ontario homes move. Between a humid August and a dry January with the furnace running, the moisture content of a plywood subfloor changes enough to expand and contract it measurably. Tile does not move. Something has to give.
What an uncoupling membrane does
A dimpled sheet — Schluter DITRA is the best known — sits between the subfloor and the tile. It bonds to both, but the dimpled structure lets the two layers shift independently by a small amount. The subfloor can move seasonally without dragging the tile with it.
When it is essential
- Any plywood or OSB subfloor. This is most second-storey and many main-floor installations across the GTA.
- Over in-floor heating. The membrane holds the cable and manages the thermal movement.
- Over a concrete slab with existing cracks. It isolates the tile from cracks that are still moving.
- Older homes generally. The 1950s and 60s bungalows across Scarborough and North York have subfloors that have been moving for seventy years.
When you might skip it
Over a sound, crack-free, fully cured concrete slab on grade with no moisture issues, you can bond tile directly. That is genuinely the only case where we would leave it out, and we would still moisture-test the slab first.
What it costs
Material is roughly $2 to $3 per square foot, plus the labour to install it. On a 200 square foot floor that is a few hundred dollars. A cracked tile floor that has to come up and go back down is several thousand. It is the cheapest insurance in the entire job.
How to tell if yours was skipped
Tap along the floor with a coin or a knuckle. A properly bonded tile sounds solid. A hollow sound means poor mortar coverage underneath. Combined with hairline cracks running in a straight line across several tiles, that usually indicates subfloor movement with nothing isolating it.
Our approach to floor tile installation includes membrane over every plywood subfloor as standard, not as an upsell.
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 floor at no cost.