Why is my bathroom tile floor uneven?

An uneven bathroom tile floor is almost always caused by one of two things: an improperly prepared subfloor before installation, or tile that was set incorrectly during the installation process. The good news is that identifying the cause helps you figure out whether this is a cosmetic fix or something that needs more serious attention.

The most common culprit is the subfloor itself. In Toronto's older homes — particularly the post-war bungalows common in Scarborough, Etobicoke, and North York, or the century homes in neighbourhoods like The Annex and Leslieville — subfloors can be made of older plywood or even diagonal board sheathing that has warped, deflected, or deteriorated over time. Tile is an unforgiving material; it needs a flat, rigid surface to bond to. If the subfloor flexes even slightly, tiles will crack, pop, or sit unevenly. A subfloor should have no more than 3mm of variation over a 3-metre span (per industry standards) before tile is installed.

The second major cause is poor installation technique. If the tile setter didn't use enough mortar, didn't back-butter the tiles, or failed to level each tile as they went, you end up with lippage — that annoying condition where tile edges sit at different heights and catch your foot or look visually off. This is especially common with larger format tiles (12x24" or bigger), which are popular right now but require a much more precise installation than smaller mosaic tiles.

Other contributing factors worth considering include:

• Moisture damage or rot beneath the tile (common around toilets and tubs in older bathrooms)
• Joists that have sagged or been notched improperly during past plumbing work
• Insufficient tile backer board — in Ontario, cement board or an equivalent uncoupling membrane like Schluter Ditra is the standard for wet areas
• Settling of the home's structure over time

From a Toronto homeowner's perspective, the fix depends entirely on the cause. If it's minor lippage from a recent install, a tile contractor may be able to grind down high edges. If the subfloor is the problem, you're likely looking at a full tile removal, subfloor repair or replacement, and reinstallation — a more significant project that could run $3,000–$8,000+ for a typical Toronto bathroom, depending on scope and materials.

You should bring in a professional if the tiles are cracking, if you feel flex or bounce when you walk on the floor, or if there's any discolouration suggesting moisture underneath. These are signs of a structural or water damage issue that won't fix itself.

As a next step, do a simple test: press on the uneven tiles and see if they move or feel hollow when tapped. A hollow sound means the bond has failed. Then take a long straightedge or level across the floor to gauge how significant the variation actually is. From there, a qualified tile contractor can assess whether it's a surface fix or a full tear-out situation.

Browse tile and flooring contractors in our directory at the Toronto Construction Network to find experienced local professionals who can assess your floor properly.