Do You Know Everything About Backer Boards?

By Steve Rausch

LATICRETE Hydro Ban Board
LATICRETE Hydro Ban Board

You would think after all these years of using backer boards in the tile industry installers should already know everything about them, yet, we still have plenty of examples of tile installations using backer boards failing to perform as expected or intended. As technology keeps changing, setting materials, tile sizes and other tile installation materials, backer board technology has a few new tricks up its sleeve.

Here are several questions for you to ponder:

·       Can you use backer boards under self-leveling concrete and then add a polishing finish wear-layer material, such as epoxy resins?

·       Are manufacturers using liquid silicates to seal the face and edges of backer boards? If so, does that affect the bond of the tile or stone being attached?

·       What is the impact of the changing materials used in backer boards, such as cementitious modifiers, increased fly ash, new or highly modified resins as bonding agents, different mixes of foams, magnesium oxide, or different aggregate base materials?

·       Is it necessary to use a membrane for waterproofing, or vapor barrier, or crack isolation when using a new generation backer board?

·       Is it still necessary to tape seams, treat corner joints, and skim patch over fasteners heads before tiling?

·       Does anyone know all the answers to these questions? Where do you go to get those answers? See the end of the story for answers.


Should the above questions be session topics for upcoming industry meetings/events? Are we, as an industry, keeping installers well-informed about the intended benefits and changing working characteristics of backer board products?

Just as setting material manufacturers hold regular training sessions about the differences in the latest setting materials, shouldn’t the same be done for backer boards? When was the last time a backer board manufacturer held a clinic at your local distributor? Do educational seminars at trade shows cover the subject of backer boards? How are backer boards made? Do manufacturers use different manufacturing processes for different types of backer boards?

Why Use Backer Boards?

Backerboards were developed for tile setting underlayment as an alternative to mortar beds or drywall. The skilled labor required to produce traditional mortar beds has grown increasingly scarce, and drywall has proven to be unsuitable for wet-area applications. The purpose of a backer board is to provide a solid, flat, support plane to which tile or stone can easily be installed and will remain bonded properly to the backer unit. Understanding this helps explain the need for proper installation, such as leaving a small gap between boards, then filling and taping those gaps to provide a solid surface for support.

Schluter Kerdi Board
Schluter Kerdi Board

Obviously, the boards must be fastened properly and securely (requiring mechanical attachment, such as screws or ring shanked nails) to the subsurface no matter if it is a floor or a wall on framing studs.

The major difference between walls and floors is that while installing walls, the board is usually hung directly onto the 16″ on-center framing studs. On floors, some type of solid material, usually plywood or OSB, is under the backer board, which requires a leveling bed of setting materials to support the board completely.

Technology Differences

Today, backer boards are made with a huge range of ingredients, including, but not limited to: cement and cement combinations, fly ash and clinker, chopped/shredded/modified foams, recycled/processed paper, highly modified gypsum, magnesium oxide materials, and various bonding agents and highly specific modifiers.

Nailing in Shower Wonderboard
Nailing in Shower Wonderboard

Over the past 30 years, many types of backer boards made from various other materials have come and gone. I expect the future will continue to introduce newly developed, technologically advanced backer boards using new materials. There are also various methods of production in the manufacturing process of different materials and types of boards. The TCNA Handbook for Ceramic, Glass, and Stone Tile Installation includes an up-to-date list of a variety of backer board types sorted by standards category.

However, a group not listed in the Handbook is the latest group of products, “liquid backer board,” which aren’t boards at all. This new group is completely and totally unproven and has no standards to ensure performance. This is truly just a marketing ploy to sell a subset of liquid membrane or leveling products when these products don’t have any of the required characteristics of backer boards, nor do they have any proof of performance in doing what a backer board is intended to accomplish. The single most important information to ensure a job doesn’t fail is to use a proven type of board, and to explicitly follow the board manufacturer’s specific installation instructions. You should never use one manufacturer’s board and follow someone else’s instructions.

Answers to the Questions

Here are the answers to the questions I asked earlier. Unfortunately, many proper answers depend entirely upon the backer board and the application of the installation.

For specific answers, I only provide you two choices. First, call the manufacturer’s technical services department to get, in writing, their response so you have proof in case of any potential failure that you, the installer, did all you possibly could to ensure a successful installation. Second, call an expert, like myself, and get our opinion. Usually experts will help you to think about the materials and the installation situation you are involved with, and guide you to the proper answer. Most often, that answer will still involve calling the manufacturer.

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