How to Install a Concrete Floor
Laying an interior concrete floor is usually a renovation project that takes place in your basement. Learn how to remove an old wood floor, prepare a base and pour a concrete floor.
With any tile job, the first step should always be to determine the pattern and orientation of the tiles in your install. It helps to open a few boxes of tiles and actually lay them out in different patterns on the floor to see what looks best. Be sure to also experiment with different grout spacings at this stage.
Before you cut and install any tiles, you need to take measurements of the floor space to make sure you’ll have enough tile to get the job done. You should measure the size of the tiles as well, so you’ll have an idea how many will lay out across the room. In addition to measuring for the number of tiles you’ll need, you should also measure to determine if the walls are square. If the walls aren’t square, which is the case in most houses, you’ll need to run chalk guidelines across the floor for your tile pattern to follow. Following these guidelines will ensure that your pattern doesn’t drift as it moves across the floor.
Often, getting the tiles to fall out perfectly is as easy as changing the grout spacing. It doesn’t seem like much space when it’s measured out an 1/8th or 1/16th of an inch at a time, but it does add up.
Depending on your pattern, you may need to start with some cut tiles. The absolute best tool for cutting tiles is a wet saw, which can usually be rented for $50 to $75 per day. They save so much time and aggravation in the long run that they’re well worth the rental fee. To make a perfect cut, use a speed square and a pencil to mark a cut line on the tile, and then slowly push the tile through the cutting area. You don’t want to force the tile, just apply enough pressure to keep the tile in contact with the blade, which will do the work for your.
Don’t cut too many tiles at once. One miscalculation of your dimensions can ruin a lot of tiles if you cut them way in advance. It’s best to cut tiles a few at a time, as needed, to keep your pattern consistent and even.
Mixing the mortar is not a tough job if you have a corded high-output power driver and a mixing paddle. Don’t try this with a cordless driver, because it will burn out the motor. If you don’t have the proper mixing tools, or if you just want to save some time and effort, you can buy pre-mixed mortar at most hardware stores, but it is more expensive.
To mix your own mortar, add a small amount of water to the bottom of a five-gallon bucket and then more the mortar mix on top of the water (Image 1). Put the mixer paddle into the bucket and start mixing at a slow speed. Add more mix and water, a little bit at a time, so that it’s easier to mix. The final consistency should be just firm enough that it doesn’t drip or run easily (Image 2). Think toothpaste.
Apply the mortar to an area of the floor, along your chalk guideline. Make sure you leave the chalk line exposed so you can use it as a guide. Use the flat side of the trowel to spread the thinset mortar on the floor (Image 1), then turn the trowel around and double back over the thinset with the notched side of the trowel (Image 2).
Don’t apply too much mortar to the floor at one time, as it will begin to set up within 20 minutes. Just work a small area at a time, spreading the mortar out and installing a few tiles before moving to the next area (Image 3). If you do have to stop for any reason after you’ve already spread the thinset down, scrape it back up and put it in the bucket. It is much easier to get off the floor while it’s wet than once it’s cured.
Typically for floor installations, a 1/4” square-notched trowel is the right tool for the job, but if your floor is rolling, uneven, or if you are working with very large tiles, it helps to use a trowel with larger notches. Recommended sizes are 3/8” and 1/2”, which are easy to find in most hardware stores.
Begin with your cut tiles in the corner of the room, following your chalk guildelines. You want to always work towards the perimeter of the room, so you can hide cuts against the wall where they’ll be less noticeable. You can use grout spacers or simply eyeball the grout lines to achieve your desired spacing.
Always work your way towards an exit, so that you can effectively tile yourself out of the room. The tile cannot be walked on for 24 hours, so it’s important that you don’t tile yourself into a corner.
It’s very important to take time to make sure the edges of your tile are level with each other. A raised corner is an unwelcome obstacle on a floor that should be flat and smooth. Take care during your install that the corners of your tile are not at different elevations from the corners of neighboring tiles. Apply more thinset to the back of tiles (or remove some) as necessary to achieve a flat, level floor.
Once the room is tiled, it needs at least a day to properly set up and cure before it can be walked upon. If you have children or even large pets, you may want to barricade the entrances of the room until the tile has properly dried.
Once the tiles are properly dried, the final step is to grout in between the tiles. Sanded grout is more durable and should be used if possible. However, very fine grout lines (1/16th of an inch or less) will require unsanded grout. Mix the grout the same way that you mixed the mortar in Step 4. Use a grout float to spread the grout evenly into the seams. Be sure coverage is thorough so there are no gaps or sunken areas. Within 10 to 15 minutes, lightly sponge off the excess and wipe down the tiles to clean them. Make sure you get any chunks of grout off the face of the tiles before it dries, as it’s much harder to remove then. Allow the grout to cure 12 to 24 hours before any intense cleaning.
After the grout has dried, it’s common to have a cloudy residue from the grout on the surface of the tiles. The best way to clean this grout film is to wipe the floors down with white vinegar, though warm water works quite well too. Do not use soap or other cleaning products.
Porcelain tile does not need to be sealed, as it’s already moisture resistant. Since the floor is not a high-moisture area like the inside of a shower, you do not need to use a grout sealer, but you may do so if you like.