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Ceramic tile floor installation
Nov 05, 2004

Question:  We are putting a bathroom in the basement and are thinking of installing ceramic tile on the floor.  Can we install it right on the concrete or do we have to put in a subfloor? 

Answer:  You can install ceramic tile right on the concrete floor if it is level and smooth.  However, any cold that comes through the concrete floor will be transferred to the surface of the tile. 

If your basement ceiling is at least six and a half feet from the floor, you could install a wood subfloor consisting of two-by-four sleepers, 16-inches on-centre and half-inch pressure treated wood.  Never set tile directly on wood.  Wood, including plywood, expands and contracts causing cracks.  

If you have a wood subfloor, install a waterproofing membrane.  It will help protect the installation by absorbing some of this movement.  

The surface of the plywood should be completely smooth, such as good-one-side fir or pine plywood or whatever the tile manufacturer recommends. Also, the surface to which tile is being applied must be flat, clean and free of dust, debris, wax and grease. Even small bumps and dips can cause cracks in tile or grout. So if an underlayment is necessary, cement board is the best choice. 

There are some precautions to take, however, when installing ceramic tiles on a subfloor. Be certain the subfloor is strong and stiff enough to support tile — some installations can weigh over eight pounds per square foot.  

But if you are using tile in a bathroom, you usually match the tile to the room size; for example, small tiles in a small room. 

Ceramic tile is classified by its porosity. Vitreous tile is the least porous and is recommended for areas where splashing is likely. Tile is also rated for use on floors or walls. Some are dual-purpose. Ask your retailer about the recommended use for the tile you have selected. 

Question:  We are going to install ceramic tile in our family room and would like to know what we can add to the grout to keep it from looking dirty? 

Answer:  You may be thinking about white grout which is often used as a sealer in bathrooms. I would recommend that you use a coloured grout that blends with the tile for floors and bathrooms, since the grout lines don’t pop out at you when the job is finished.  

The professionals use a special sanded, wet/cured colour grout. This type of grout comes in a powder form and is mixed with water or a special liquid.  The special liquid allows the grout to flex slightly. It also makes the grout stainproof, waterproof, etc.

The floor tile must be compatible with this type of grout. Make sure of this before you start your application. This grout cures quickly, does not shrink and is relatively easy to use.  

Be sure that the tiles are firmly set and mix the grout according to instructions.  The grout is then the consistency of thick butter.

Fill the joints using a rubber float and remove excess grout. Sprinkle dry grout on the joints and rub it in with a burlap pad using a circular motion until the joint is smooth and flush with the tiles.  

Since this grout has a Portland cement base, it is best to keep it damp for at least 72 hours so that it can cure properly.  After curing, the floor can be cleaned with the solution recommended by the grout supplier. 

Ceramic tile specialty stores and home hardware centres can supply you with additional information.