How to Install Concrete Backerboard: Advice on Choosing the Right Subfloor for Floor Tiles


Concrete backer board, also known as Rhino Board, has emerged as a popular alternative to plywood subflooring. Rhino Board can be up to four inches thick but is more commonly seen in plywood-like thicknesses of 1/4″, 3/8″, 1/2″, and 3/4″. After scoring the outside with a hand tool like a carbide cutting blade, the board can be put, score side up, directly over an object like a copper pipe for easy cutting. Standing with one foot on either side of the score and applying equal weight and pressure, it is quickly snapped in two.

The score can be made with a knife, although doing so will quickly dull the blade. If you want a cleaner break, you may need to make a few more scores; once the first crack is made, you can fold the board in half to separate the two halves; however, you may find that additional scoring on the other side is necessary to split the seam completely.

Because they are essentially just sheets of concrete created over a mesh and housed within a paper-like substance, these boards are incredibly robust to compensate for the downward pressure required for flooring. Still, they are also very brittle, which allows for the ease of breaking. It’s conceptually similar to plaster board and dry lining, but it’s far more durable and sturdy. However, due to their weight, concrete backer boards can be challenging.

As a result, it’s preferable to lay this sort of backer board with its broken edges away from the interior walls wherever possible. In the same way, you would when building plywood subfloors, you should alternate the direction of your seams. Fasten to the subfloor with screws every 4 inches along the perimeter and every 8 inches inward, using the same grid pattern as the existing floor. However, the concrete backer board is so fragile that screws driven into the edge quickly shatter and fail to keep the material in place. To avoid this, it’s recommended that objects be placed at least 1-1/2 inches inward from the edge.

Using a 3/8″ by 1/4″ notched trowel, you must put down a mortar bed before installing your concrete backer boards as a subfloor. Without breaking the bank, you can get by with plain old mortar for floor tiles. Without waiting for the mortar to cure, you may immediately lay down the backer board on top of it, screw it down onto the primary flooring, and start walking on it or even move straight into tiling, provided that you have first filled and leveled any dips and seams.

Compared to plywood subfloors, these can be easier to install, and they are much less likely to shift and swell, which can cause harm to the tiles on top. However, the concrete backer board, the specialized fasteners needed for installation, and the surplus mortar all add up to a hefty price tag. Depending on your chosen brand, not all concrete board manufacturers will tell you that you need special mesh tape to finish the flooring installation.

Although many professionals in the floor-tiling industry insist on using this subfloor installation method, the truth is that wire mesh subfloors, plywood subfloors, and concrete board subfloors have all been shown to perform well and will continue to do so over time. If you aren’t lucky enough to be tiling directly onto a concrete floor, it’s up to you to figure out which option is best for your preferences and budget.

Matt is a doting father to his 2-and-a-half-year-old daughter and soon-to-be-born son. He and his wife now reside in a house built in the 1950s and renovated by him in his “spare time” over several years. He has a dual interest in floor tiling and extreme activities, which don’t go together but contribute to his confident demeanor and willingness to take on challenges.

The book “A Unique Step-by-Step Guide: Making Floor Tiling Easier,” which Matt spent nearly three years writing, was finally published. He aimed to simplify the process so that users of all skill levels could use it successfully.

If you go to, you can buy the book or get a free DVD on a tile floor. To learn more about the exclusive offer he is making, select the FREE DVD.

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