Prepping concrete for tile
- thattilechick
- Jul 17, 2022
- 5 min read
What you need to successfully install tile over concrete and prevent tiles from cracking.
Intro:
This post is all about what you will need to prepare to lay tile over concrete. We will go over using the Schluter Ditra uncoupling membrane also known as an underlayment for tile.
If you are new to tile installation world, watch this video for a full walkthrough of what you need to do to lay tile over concrete before starting your next project!
Why you need underlayment for tile:
Depending on your subfloor (The floor surface you are tiling to) you may need to take some precautionary steps before setting tile. Sometimes you will have a concrete subfloor or “slab on grade” like I will be demonstrating here OR you will have a wooden subfloor. A wooden subfloor can either be on the first floor of your home which would indicate your home is built on “pier and beam or block and beam” you may even have a crawl space. Sometimes the wooden subfloor is on the second story of the home. If you are trying to tile over a wooden subfloor, check out my Youtube Video Here.
Why I am installing an uncoupling membrane (underlayment for tile) over concrete:
An uncoupling membrane is very important as it helps prevent tiles from cracking when installing on top of concrete. Concrete naturally expands and contracts; by using the uncoupling underlayment, it mitigates this movement from cracking the tiles after installation. This is applied directly to the concrete with thin set.
Quick links:
5. Hi Efficiency dust bag for vac - this contains the small dust particles.
9. Floor roller
Process:
The first step in tackling concrete prep is using a grinder to remove any old paint, debris, or material that may be stuck to the concrete. Here is an example of what the concrete may look like before beginning the grinding process.
As you can see, the flooring that was there prior left some thin set on the concrete as well as some paint. You never want to lay tile underlayment or tile directly on a dirty and unprepped subfloor. Debris, old paint, and dust will cause poor adhesion for the thin set and can create a failure in your tile installation down the road such as cracked for even loose tile.
We can prep the concrete using the 7’ floor grinder, the goal is to remove all of this material from the concrete so that it is clean. When you complete the grinding, the concrete floor should look clean and have a scuffed surface. This is similar to sanding furniture before painting. It creates a better prepped surface for thin set to adhere to.
Below is an example of a concrete floor that has been grinded to remove any debris.
After the grinding is complete and your concrete floor is free from debris, the next step in the process is to check for flatness. Before setting tile to a floor, you need to make sure its flat or level. Flat is when all parts of the floor are touching the bottom of the level.
** It is extremely important that you are using the proper sized level. For example, If you have a room that is 10 ft. in any direction do NOT use a 2ft level. This will not give you an accurate read of the floor and can result in poor preparation. I always like to check at least an 8ft span if my room is over 8ft.** You can get any size level here.
When checking the floor for flatness or level there may be high spots that are not too significant, they can be remedied by using the grinder. Any low spots you find may have to be filled in with a patching compound.
Once you have resolved any high or low spots on your concrete it is time to dry fit your underlayment. In this case we are using the Schluter Ditra uncoupling membrane. You can easily cut this with scissors or a pocket knife. I like to section off the room to get small working areas so that my thin set does not get dry.
Pro Tip: Be very careful when installing this. You want to make sure you work quick enough that the thin set doesn’t dry on you. If it is too dry you will not get the proper coverage between the substrate and the underlayment.
Keep in mind that concrete likes to absorb moisture, it is recommended to wipe the concrete floor with a damp sponge to prevent the concrete from quickly absorbing the moisture from the thin set and removing any additional dust that may have settled on the floor. This also gives you some extra time to apply the membrane as the floor won’t pull out the moisture from the thin set as fast.
Pro Tip: Make sure to check the instructions from the manufacturer of your uncoupling membrane to see what thin set they recommend using with their product and any important installation instructions they may have. These steps in this blog are pretty universal for any uncoupling membrane on the market but I always recommend checking with each specific manufacturer. You can get a warranty if the proper installation materials are used.
Applying the thin set
Apply your thin set along the subfloor in one direction. For the brand of membrane I used, they recommend mixing the thin set on the looser side, but once again, make sure to check the instructions of your membrane you chose to use as that may not always be the case.
After I have the thin set applied, I can lay down the underlayment (Schluter Ditra uncoupling membrane) and use a roller to collapse the ridges under and form a good bond.
As you use the roller to apply pressure, you will see the thin set will transfer to the back of the membrane forming the bond we are looking for. Repeat the same process for the rest of the sections of the floor until it is fully covered with the uncoupling membrane. It is important to make sure you are collapsing the ridged behind the membrane as to get all the air out and get full coverage.
Here is what my floor looked like after laying down all the uncoupling membrane. As soon as you are done laying the underlayment or uncoupling membrane, you are ready to set tile.
This post was all about what you need to set tile over concrete. We installed the Schluter Ditra uncoupling membrane over our concrete subfloor before setting tile.
If you are planning on installing tile yourself, or looking to hire someone and want to make sure the job gets done right you can check out my video here going over this process as well.
Thanks for reading<3
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