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Ceramic Tile Installation – Subfloors and Underlayment

A subfloor is essentially the structural support for the floor while the underlayment is the foundation for the ceramic tile installation that’s placed on top of the subfloor to give the ceramic tiles a good working base.

It’s very important to know what kind of subfloor you will be working on, since this will greatly help you choose the best underlayment for the working area to prevent the tiles from cracking or failing in the end.

The most common subfloors that you will encounter are:

Concrete Subfloor

A concrete floor is one of the most common types and it’s very good to have for ceramic tile installations. It’s important to check the condition of the concrete to make sure it’s a suitable state prior to preparations for the tiles.

Clean the concrete subfloor, making sure to get rid of any debris or small pieces and fill in all cracks or gaps that are showing. This floor must be smooth and level for a sound finished floor.

Tile Subfloor

If your subfloor is previously existing tiles, you have two options to choose from before going ahead with your tiling work.

The first option is to leave the tiles as they are, but just clean and prep them prior to tiling, and the second option is to chisel the old tiles away and clean the surface anew.

Plywood Subfloor

Always check the condition of the current subfloor if it’s plywood. It’s generally recommended to have two layers of outdoor grade plywood but if you find damaged areas or weak spots, consider removing it completely or placing a stronger underlayment on top of it like backer board for good solid support. kitchen backsplash

To see which type of underlayment would work best for your ceramic tile installation, learn more about the common types available:


Although plywood is not the top recommended choice for underlayment, it’s certainly one of the more popular choices around. Always make sure you have outdoor grade plywood when applying it as an underlayment since the regular grade will succumb to moisture and eventually rot beneath the tiles.

Oriented Strand Board (OSB)

Very similar to plywood, OSB is quickly becoming a favorite as a flooring underlayment since it’s tougher, water-resistant and does not have any gaps between the sheets, which makes it ideal for indoor use.

Although it is water-resistant, it’s recommended to apply a thin sheet of plastic on top to make it water impermeable, which better suits rooms like kitchens and bathrooms.

Backer board

These pre-fabricated sheets of material are lightweight, tough and durable for a good solid floor base. Usually made of a thin concrete layer or cement fiber combination, they are generally used in areas that tend to get a lot of moisture.

Mortar Bed

When hiring professional contractors, they will almost always use a mortar bed as the underlay for ceramic tile installations since they believe it’s the best possible base for a solid tiling job. There are other materials that will work just as well and can also be placed much faster for a solid flooring base.

If you plan on placing a mortar bed yourself, make sure you have all of the necessary tools and materials along with a step-by-step guide since they can be very difficult to complete properly, especially when trying to create an even thickness for first timers.


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