Q&A / 

Ceramic Floor Tile Installation Tips and Secrets

DEAR TIM: My husband and I are deep into installing new flooring in our home. Flood damage ruined the carpet. We decided to install a combination of laminate flooring and ceramic tile. The tile work is much harder than I thought. We're installing the large tile directly on top of the concrete slab. I'm using plastic spacers to keep the grout lines straight, but I'm having great difficulty. I've never grouted before and am worried about messing that up. Help! I don't want to ruin this project. Marilyn H. New Bern, NC

DEAR MARILYN: I'm sorry about your recent disaster, but I'm happy that you've bounced back with a great DIY attitude. In my opinion, self-sufficiency and do-it-yourself is part of what built our great nation. You're going to be very proud of your work once it's complete. I also want to add that it's beneficial to push against your comfort-zone envelope and be slightly uncomfortable. That's how you improve your skills.

The first thing I want to mention is it's impossible to come close to communicating all you need to know about this ceramic tile job. Many a book and thick instruction manual has been written about the art of installing ceramic floor tile.

I'm going to try to cover the most important points and share a few secrets I've discovered in the forty years I've installed tile of all types. Realize that you could ask ten tile pros a question and you very likely could get six or seven answers - all of which may produce excellent final results. There's usually several right ways to achieve professional results.

Ceramic tile is a very rigid product that has a high compressive strength. This means you can squeeze it and it won't crush. However, ceramic tile, concrete, and natural stone have low tensile strength. This means if you try to bend a piece of tile, it doesn't take much effort to crack or snap it.

To prevent cracked floor tile, you need to make sure there are no void spaces between the tile and the floor surface it rests on. A void space under a tile will cause the tile to bend as you apply pressure to the top of the tile. The larger the tile you're installing, the more difficult this task becomes as it's very hard to get a floor surface in the same plane. You can use fantastic pourable self-leveling floor compounds to get a perfectly flat floor surface if you plan ahead.

Cracks in a concrete slab can, and often do, telegraph through the floor tile. If your slab has cracks, consider using special injectable concrete epoxies to repair the cracks so the concrete doesn't move. Professionals often install crack-isolation membranes between the tile and concrete slabs. These help keep ceramic tile crack-free for the life of the floor.

This patterned ceramic tile floor is well on it's way to completion. The plastic spacers could cause problems Photo Credit: Marilyn H., New Bern, NC

This patterned ceramic tile floor is well on it's way to completion. The plastic spacers could cause problems Photo Credit: Marilyn H., New Bern, NC

I discovered long ago the plastic spacers used to keep grout lines straight don't always work as intended. It's not because the spacers are defective. Realize the spacers are probably manufactured with very tight tolerances, but the ceramic tile may be off slightly. If you have a variance of just 1/32 inch between tiles, that can create a 1/16-inch difference if two of those tiles are installed side-by-side. Pretty soon the grout lines will look more like a sinuous stream channel if you use the plastic spacers.

My preferred method of installing floor tile is to create a grid on the floor using a chalkline. I calculate the exact distance, based on the width of the tile and the grout line spacing I want for either a 3 x 3 tile grid or possibly a 4 x 4 tile grid. I snap the lines making sure they're accurate and lay the tile to the edges of the grid lines. The center tile are just installed by sight making sure the grout lines are consistent and straight.

Realize that prior to the grout being installed the lines between the tiles may appear slightly less than perfect. Grout has a magical quality to mask these very slight imperfections. Twisted or crooked tiles will still look twisted and crooked with grout.

When you get ready to grout, you can spoil all your hard work up to this point. Rookie tile setters often make any number of mistakes when mixing, applying or finishing the grout. I recommend that you purchase some very inexpensive floor tiles and install them on a 3 x 5 piece of cement backer board that just is laying in your garage. Practice grouting on this test area until you perfect your skills.

Mix the grout so it's the consistency of bricklayer's mortar. If it flows from a bucket like pancake batter, it's too wet. Too much water when mixing or finishing the grout joints weakens the grout. This will cause it to crack or crumble in the months ahead.

Apply the grout with a hard-rubber float at a 30 or 45-degree angle to the grout lines. This diagonal stroke will ensure the grout is flush with the top of the tile. Do not rub the grout with the sponge until it firms up enough so you don't remove grout from the joints.

Low humidity and hot temperatures will cause floor grout to set up rapidly making it very hard to finish. You need to discover on your own how much grout you can install and finish at one time. Only mix enough grout in a bucket that you can install and finish in one hour. You can always mix more. Don't add water to stiff grout in the bucket. Re-tempering the grout with water will weaken it.

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