Tiling Bathroom Floor

Tips on Installing Bathroom Floor Tile

By Mark J. Donovan

Last weekend I spent much of it tiling a bathroom floor. The weekend prior I prepared the subfloor by removing the old linoleum, rough sanding the subfloor, and installing additional screws into the subfloor. The subfloor was a ¼” Luan based material resting on ¾” tongue and groove plywood. Though I have heard complaints of installing ceramic tile on Luan, I have never experienced a problem with loosening tiles on a Luan base. I believe as long as the floor is solid and the Luan surface is roughed up sufficiently with sandpaper the ceramic tiles will adhere well.

This all said, when tiling a bathroom floor, or any floor, it is important that the base subfloor be extremely solid and have no perceivable deflections. In addition, when tiling a bathroom floor it is important to use a latex modified thinset mortar versus a mastic. The thinset mortar will not degrade with exposure to water whereas with mastic, water can break it down and cause the ceramic tiles to become loose. Also, I always install coarse thread decking or drywall screws on 6” centers across the entire subfloor surface. This helps to make sure the Luan is securely fastened to the subfloor plywood.

When tiling a bathroom floor it is always important to first layout the tiles in an X-Y direction to see where tiles will be cut. Also take into consideration joint spaces. I used 12”x12” ceramic floor tiles and used a ¼” spacing between tiles. Typically you want to locate cut tiles in less observed areas. Once you have figured out roughly where to start your tiles to minimize viewable cut tiles, draw straight and perpendicular center X-Y lines as reference points on the subfloor. You may want to draw additional parallel lines to these main X-Y center lines to help maintain straight lines when installing the tiles outwards from the center of the bathroom floor. In addition, you may want to purchase some tile spacers to ensure even joint lines.

After establishing your reference lines, mix up your latex modified thinset mortar and begin to install tiles. Make sure to not mix up too much thinset mortar at any one time, and do not continue to add water to the mortar if it begins to thicken up. Doing so will weaken the bonding agents in the mortar.

Start by installing tiles from the cross-hairs of your center line and working your way in one direction outwards to a wall. Make your cuts along the wall to complete the first part of the bathroom floor tiling.

Then continue to install ceramic bathroom floor tiles in the opposite direction from your reference lines to complete the tile installation.

Once you’ve completed tiling the bathroom floor, allow the thinset mortar to set up for 24 hours before grouting.