How to Install 12 x 24 Tile: Layout, Trowel Size, and Grout Width | Getting The Notch Right

For the full breakdown, see our best 12 X 24 Tile guide.

Setting a 12 x 24 tile so it stays flat and gap-free comes down to three numbers: the trowel notch, the grout joint, and how flat the floor already is. Get the notch too small and the tile bridges over hollow spots that crack under a heel later. Force the joint too tight on calibrated tile and the corners chip each other. The steps for how to install 12 x 24 tile get easier once those three numbers line up.

What Trowel Size Does 12 x 24 Tile Need?

A 12 x 24 inch tile counts as large-format, so it takes a bigger notch than a subway tile. Most U.S. floors run a 1/4 x 1/2 inch U-notch, with a 1/2 x 1/2 inch square-notch handling the same job on many installs.

The notch size controls how much thin-set lands under the tile once you comb it and press the tile down. Undercut it and you get voids — pockets of air the tile flexes over. Bigger tile means more area to cover, so the ridges have farther to spread before they collapse flat.

Two habits do most of the work:

• Back-butter the tile, skimming the back with the flat side of the trowel so the ridges have something to marry into.
• Comb the thin-set in one direction, hold the trowel at a steady angle, and don’t scrape the ridges flat.

Custom Building Products notes that a 1/2 x 1/2 x 1/2 inch square-notch trowel can save time and labor against smaller notches on large-format jobs. Pull one tile after setting it and check the back: full, even contact is the goal.