When you decide to change the tiles in your kitchen or bathroom, make sure that your underlying structure is solid enough. Problems with installing new tiles are usually caused by inadequate subfloor preparation.
To help understand what preparing a subfloor requires, we have summarized the different possibilities.
To begin, it is important to note that subfloor preparation varies depending on the structural base. If the base of the floor is made of wood, the preparation is different than it would be for a concrete base.
Preparing a subfloor on a wood base
If the base of your subfloor is made of wood, there are four ways to prepare your subfloor. The way the structure of your house was built will have an impact on what has to be done.
If the joists of your house were placed every 16”, your subfloor base should be made of 5/8” plywood or OSB (oriented strand board), to which you must add another layer. If it is plywood, you need to add a second 5/8” plywood, with screws driven every 6”. If your substrate is OSB, then you need to install an uncoupling membrane, glued with a polymer-modified mortar.
If the joists in your house are installed every 19.2”, your subfloor base should be made of ¾” plywood or OSB. Again, a second layer has to be added. If the base is plywood, you need to add a second ¾” sheet of plywood, with screws driven every 6”. If it is OSB, then you need to install an uncoupling membrane, glued with a polymer-modified mortar.
If the joints in your house are installed every 24”, your subfloor base should be made of ¾” plywood or OSB. If the base is plywood, you need to add a second ¾”sheet of plywood, with screws driven every 6”. If it is OSB, then you need to add a second 3/8” thick sheet of OSB, then you need to install an uncoupling membrane, glued with a polymer-modified mortar glue.
If you have an older house, it is highly probable that the substrate installed on your joists is made of structural planks (wooden planks of various widths and lengths). If this is the case, you need to add a second layer of ½” substrate (plywood orOBS) and then you need to install an uncoupling membrane, glued with a polymer-modified mortar glue.
Preparing a subfloor on a cement base
You can install tiles on cement, as long as it is in good condition: clean, dry, without any moisture problems, glue or cleaning product residue. There is no particular preparation required since the cement is in its natural state.However, it is advisable to install an uncoupling membrane before installing tiles. The membrane is protective and will prevent any cracks or other problems.
Other surface types
Not very many people know that you can install new tiles on top of existing vinyl or tiles. If you decide to do this, it is important that the vinyl isn’t padded, that it was glued down when it was installed and that there is only one layer. Tiles are a rigid floor covering, so they must be installed on a solid base that doesn’t move.
The preparation required in this case involves applying a degreaser to eliminate any trace of wax, cleaning product residues or dirt. Once you have done this, you have to install an uncoupling membrane on the vinyl with a quick-setting modified adhesive mortar. A few hours later, you can install your new tiles.
If you choose this option, you need to keep in mind the final height of your new floor. On average, tiles are 3/8’’(10 mm) thick, which means that your floor will be at least 3/8” higher, and that your other flooring won’t necessarily be the same height.
Regardless of the base on which your tiles will be installed, your subfloor must be flat.Ceramic tiles are rigid and do not have any give for movement. It is therefore important that your floor be as flat as possible to ensure good adhesion between the tile and the mortar. A 1/8” over 10’ slope is acceptable; however, if the slope is greater, you must level your subfloor. You can do this using self-leveling mortar.
In conclusion, no matter what your subfloor is made of, if you want to prepare it yourself, make sure to talk to a renovation professional or a tiler about how to go about it. Their knowledge and expertise can go a long way to help you avoid a lot of headaches!