How to Tile a Floor

Tiling a floor is one of the more demanding DIY projects - the prep work is tedious and the window for adjustments closes once the thinset cures - but a well-tiled floor lasts 30-50 years. The difference between a professional result and a visible DIY job almost always comes down to substrate prep and layout planning.

Step 1: Calculate Tiles and Grout

Use the Tile Calculator to get the number of tiles needed with waste allowance (10% for straight lay, 15% for diagonal). Then use the Grout Calculator to get the exact bag count. Buy all tiles from the same lot number.

Step 2: Prepare the Substrate

The substrate must be flat, stiff, and waterproof for wet areas. For wood subfloors, install 1/4 inch cement board over plywood. For concrete, fill cracks and level low spots with self-leveling underlayment. Test moisture before tiling.

Step 3: Plan the Layout

Find the center of the room and snap chalk lines. Dry-lay tiles from the center in all four directions to check border widths. Adjust so no border tile is less than half a tile width - slivers at the wall look unfinished.

Step 4: Mix and Apply Thinset

Mix thinset to a peanut butter consistency. Apply with a notched trowel at 45 degrees. Notch size depends on tile size: 1/4 inch square notch for tiles under 8 inches; 1/4 by 3/8 inch for 8-16 inch tiles. Back-butter large-format tiles as well.

Step 5: Set the Tiles

Press tiles firmly into thinset with a slight twisting motion to collapse the ridges. Use plastic tile spacers. Check tiles frequently with a level - a 1/8 inch variation is acceptable. Wipe thinset off tile faces immediately.

Step 6: Cut Tiles for Borders

Use a wet saw for straight cuts in ceramic and porcelain (rent for $50-$80/day). For curves around pipes, use a tile nipper or angle grinder. Measure every border tile individually - rooms are rarely perfectly square.

Step 7: Grout the Joints

Wait 24 hours after tiling before grouting. Apply diagonally across the joints with a rubber grout float, pressing firmly. Remove excess by holding the float at 45 degrees. Clean with a barely damp sponge after 15-20 minutes. Buff haze off with a dry cloth.

Step 8: Seal and Finish

Cement-based grout must be sealed after it cures (72 hours minimum). Apply grout sealer and wipe excess off tiles immediately. Reseal every 1-2 years. Caulk all corners and transitions - never grout corners, which crack due to movement.

Pro Tips

• Back-butter large-format tiles in addition to troweling the floor.
• Let thinset cure fully before grouting.
• Never use sanded grout on polished marble or glass tile.
• Caulk all inside corners with matching color silicone caulk.
• A wet saw rental is mandatory for porcelain tile.