Large format tile installation means setting porcelain or stone tiles with at least one edge of 15 inches or more, and the result depends on the floor underneath more than on the tile itself. In the Lower Mainland, many condos sit on older concrete slabs and many houses have wood joists that flex, so a floor that looks level is often out of flat by more than large tile will tolerate.
This guide covers flatness limits, lippage, mortar coverage and subfloors. Homeowners planning a floor can see the surfaces we install on our flooring services page.
How flat does a floor need to be for large-format tile?
A floor under large-format tile must be flat to within 1/8 inch over 10 feet and 1/16 inch over any 24 inches, which is tighter than the 1/4 inch over 10 feet allowed for small tile. A long rectangle bridges the dips that a mosaic would follow, so every hump or hollow shows up as a rocking tile or a raised corner. Flat is not the same as level: a floor can slope an inch across a room and still pass, as long as the slope is gradual.
On a Lower Mainland job we check the floor with a 10-foot straightedge before the tile is ordered. We pencil the high spots, grind them down, and fill the low spots with self-leveling compound that cures for 24 hours before any tile goes on. Flattening adds a day or more and a line item many quotes leave out, and skipping it is the most common reason a large-format floor fails.

What causes lippage, and how much is acceptable?
Lippage is the height difference between two neighbouring tiles, and the TCNA handbook allows about 1/32 inch between rectified porcelain tiles with narrow grout joints. At 1/16 inch a bare foot can feel the edge, and low light from a window shows it from across the room. Large tiles are rarely perfectly flat themselves: a 24 by 48 inch porcelain tile can bow 1/16 inch or more from the factory, and a flat floor cannot fix that.
We set tiles with a clip-and-wedge leveling system, and we offset long rectangles by no more than one third of the length, because a 50 percent offset lines up the bowed ends of the tile with the middle of its neighbour. The downside is time: the clips stay in the mortar for 24 hours, so the floor is off limits for a day before the caps are knocked off.

How much mortar coverage does large-format tile need?
Large-format tile needs at least 95 percent mortar coverage in wet areas such as showers and 80 percent in dry areas, and it only reaches that with a large-notch trowel and back-buttering. A 12 by 24 inch tile set with a standard 1/4 inch notch leaves voids that sound hollow and crack at the edges. We use a 1/2 inch square-notch trowel with a medium-bed mortar made for tiles over 15 inches, comb the ridges in one direction, and skim a flat coat on the back of every tile.
Every few rows we lift a freshly set tile and look at its back. If the mortar ridges are still standing, the mortar has skinned over and the tile was bedded too late. Weight is the other cost. A 24 by 48 inch porcelain tile weighs about 25 pounds and chips when carried on its edge, so it needs two people and a flat stack on site. Rectified porcelain is the usual choice, and our porcelain vs ceramic tile comparison explains why.

Does the subfloor matter for large-format tile in the Lower Mainland?
Yes. A wood subfloor must deflect no more than L/360 under load for ceramic and porcelain tile and L/720 for natural stone, and thin plywood over 16 inch joists in older Vancouver and Burnaby homes often misses the stricter number. Adding a second layer of 1/2 inch plywood, screwed rather than nailed, stiffens the floor before any tile goes down.
An uncoupling membrane such as Schluter DITRA, about 1/8 inch thick, absorbs movement between the subfloor and the tile, but it does not correct a hump. We install Schluter systems to the manufacturer’s instructions, which is what the Schluter warranty is built on. Our guide to a proper tile installation in Richmond walks through subfloor prep in more detail. If you are searching for a tile installer near me in the Lower Mainland, ask whether they check flatness with a straightedge before they quote.
Frequently Asked Questions
How long does large format tile installation take?
A 100-square-foot floor with prep usually takes three to five days: one for grinding and leveling, one or two for setting, and one for grout. Self-leveling compound needs 24 hours to cure before tile goes on.
Can you install large-format tile over existing tile?
Yes, if the old tile is bonded, flat to the same 1/8 inch over 10 feet limit, and clean. We tap-test for hollow spots and use a bonding primer, and the new floor sits roughly 3/8 inch higher, which matters at doors and appliances.
What grout joint size works for large-format tile?
Use at least 1/8 inch for rectified tile and 3/16 inch for non-rectified tile. A narrower joint shows every bit of lippage, and a wider one gives the tile room to move.

Ready to check your floor before you buy tile?
The cheapest time to find a flatness problem is before the tile arrives. Visit the RT Home Renovations showroom to see large-format samples, then book a floor check at your home.
Contact us or call us at 604.781.2510 to arrange a straightedge check and a firm quote.












