How to Install Slate Tile Over Concrete
Slate tile is a durable and inexpensive material for resurfacing concrete basement floors or concrete patios. There are a few differences between installing slate tile outdoors or indoors, but overall, slate tile is fairly simple to install.
The first step is to clean the concrete floor before you install slate tile, and check for cracks, unevenness, and expansion joints. If the concrete surface is very uneven or badly damaged, you should hire a professional contractor to resurface the floor since you will need heavy machinery to remove the floor. If the floor is in good condition, you can make this a DIY project.
If your indoor concrete floor has cracks, fill them with mortar and let the mortar dry completely before laying slate tiles. If your outdoor concrete patio has expansion joints, do not fill them in. These must remain open after the project is completed. Once the cracks have been filled, determine if the floor is even enough so that you can lay an even mortar base, or if you should use cement backer board below the mortar.
Cement backer board is a stiff material that you can install on uneven floor surfaces so that mortar and slate tiles can be laid level. It is unnecessary for a concrete floor in good condition, and is not well-suited for outdoor use.
Next, find the center of the room. Draw two chalk lines, each perpendicular to a pair of opposing walls, that cross in the center of the room. Lay the dry tiles with 1/2 inch spacers, starting from the center and using the chalk lines as a guide for the proper angle. Do not cement them yet, just lay them in a practice run. Stop when you reach the walls and there is no more room for whole tiles.
Determine how many tiles you need to cut, and use a diamond blade wet saw to cut them. Lay them in place with spacers.
After you arrange the slate tiles without mortar and cement, go to the back of the room (the wall opposite the door) and start laying the mortar. Use a trowel with 1/2 inch notches to lay a level coat on the concrete or cement backer board. Press the tiles in place, using a wooden board and rubber mallet to tap them level. Work your way toward the door. Wipe off excess mortar with a damp cloth.
After the slate tiles have set for at least 24 hours, fill the spaces with grout. Sanded grout is traditional for slate tile, and most contractors recommended it. For an outdoor job with expansion joints, you should know that no matter what kind of grout you use, it will eventually crack.
The floor will be ready to walk on 24 hours after grouting. When the tile has been cured for at least two weeks you can apply an optional coat of sealant.
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