Fiberock Aqua Tough Underlayment by USG is an example of fiber-reinforced gypsum backerboard.


Custom Building Products’ Wonderboard was the first cementitious backer unit to be introduced to the tile industry.
In 1968 the Detroit Tigers won an incredible seven game World Series over the St. Louis Cardinals in baseball. In football the Green Bay Packers were putting the finishing touches on the Vince Lombardi era, winning their second Super Bowl in a row. In politics, Civil Rights, Vietnam, and Richard Nixon dominated the television screen.

While all of this was going on, a couple of men in Ohio were changing our industry at that very moment. Paul Dinkel, a tile contractor with a vision, was determined to find a solution to the problem of ceramic tile failures when it was installed over sheetrock. He began experimenting with a glass mesh mortar unit, consisting of a lightweight concrete core covered on each side with a special fiberglass mesh. It would become known as Wonderboard. Together, with his partner Ted Clear, they revolutionized the tile industry with this product. Today, a wide range of products has been developed since Wonderboard's inception, and we refer to them today as backerboards.



New Method Designed For Tub Enclosures in dry or limited wet areas.
Currently, there are five specific types of backerboards recognized by the Tile Council of North America Handbook for the Installation of Ceramic Tile. This includes several new methods recently introduced in the 2005 version of the Handbook. Contractors and sales professionals are constantly asking us our opinion on what type of backerboard to use in certain situations. Our response is understandably guarded. Each one of these products, when installed according to their specific instructions, generally will perform extremely well. It is vitally important that you study the limitations and recommended uses for each of these products.



New Method for Floors 8”x8” or larger in wet or dry areas over structurally sound plywood.
It is also important to outline this note taken from the TCA Handbook under the definitions of Backer Board types: "The Handbook Conference acknowledged other backer units that are on the market for use as a backing and underlayment with ceramic tile. However, the conferees felt there was insufficient experience and test data available to consider specific comment as to their use. Follow manufacturer's recommendations."

This is important because often there are products out there being marketed and installed that are not currently recognized by this committee. This does not mean they will not work; only that our caution is that you request written guarantees and instructions to use a product of this nature.



New Method for Interior Walls in dry or limited water exposure areas.
Backerboards are used for both floor and wall installations, and represent a large percentage of the total ceramic tile market in relation to substrate use. It is important that the types of backerboards currently recognized in our industry are defined and understood. Even today, there is much misinformation being shared in the field in relation to these products characteristics and performance.

A great example of this relates to the general recommendation by most backerboard manufacturers that you use either a dry-set or latex-Portland cement mortar to bond the product to the subfloor. For years this was explained by many in the industry as a superior way to bond the board to the subfloor, creating a more rigid surface for tile. In truth, the reason for this recommendation is that the mortar assists in providing a leveling bed to the surface, allowing for the installation to meet specified subsurface tolerances requirements of 1/4-inch in ten feet and 1/16-inch in one foot to meet American National Standards specifications.



Wedi building panel systems is an example of a cementitious coated foam backerboard.
Additionally, we often are asked if applying mortar to the subfloor prior to installing the backerboard is a requirement. The answer is complicated, because the TCNA Handbook details this practice in all approved methods, but if the manufacturers state in their literature or instructions that it is okay to eliminate this step in the installation you will have to determine how to proceed. This is the type of situation where I would suggest you require written installation instructions for this product.

In an attempt to shed some light on what types of backerboards are currently recognized in the TCNA Handbook, and what products fit into these categories, the NTCA published a document in its Reference Manual Problem Solving Guide. This document was published in 2005 with the intent of assisting industry professionals in the dissemination of the marketing literature being offered to the trade. It is not the intention of NTCA to determine what product fits into each category. This is the responsibility of the manufacturer. However, understanding the specific types is important in order to make decisions regarding what products to use in different installations.



EZ Grid by James Hardie Building Products is an example of a fiber-cement underlayment.
Backerboard Definitions
As per the 2005 TCNA Handbook: Consult with TCNA Handbook for specific installation details and the manufacturer for their complete instructions and information.

Cementitious Backer Unit (CBU)
A cement substrate designed for use with ceramic tile in wet or dry areas. Available in various lengths, this material can be applied over studs and sub flooring. Ceramic tile can be bonded to it with dry-set, latex-Portland cement, organic adhesives or epoxies. Complete interior installation and material specifications are contained in ANSI A108.11.

Specific things to look for when using cementitious backer units include the composition of the core aggregate of the board and the amount of fiberglass mesh used on both sides to hold it together. Consult manufacturer for recommendations regarding the type of mortar to install the board and whether a vapor barrier should be applied behind it. In addition, pay close attention to the type of fasteners recommended to adhere it to the subfloor or studs, so that they are non-corrosive. This applies to all types of backerboards being discussed in this article.



Permabase by National Gypsum is considered to be a cementitious backer unit.
Coated Glass Mat Water-Resistant Gypsum Backerboard
A backerboard designed for use on floors, walls, and ceilings in wet or dry areas. This material is applied vertically, directly to wood or metal studs. Follow the manufacturer's instructions for installation and joint treatment. Ceramic tile can be bonded with dry-set or latex-Portland cement mortar or organic adhesive by following these instructions.

Due to the fact that this product has a moisture barrier coating applied to its core, a vapor barrier will more than likely not be recommended for application behind the board.

Fiber-Cement Underlayments
A dispersed fiber-reinforced cement backerboard and underlayment designed for use with ceramic tile in wet or dry areas. These products are available in various lengths, widths, and thicknesses. This material can be applied vertically over studs and over code-compliant subflooring. Ceramic tile can be bonded to it with latex-Portland cement mortar or organic adhesives. General interior installation and material specifications are contained in ANSI A108.11 and ASTM C-1288. Consult the manufacturer's written literature for specific application details.

It is important to note that although these products may not look like cement, they indeed include a cement core that is fiber-reinforced. This does give it different characteristics than other products that may appear to look like them.

Cementitious-Coated Foam Backerboard:
There is a new method for this category recently approved in the TCNA Handbook in 2005. Method F175-05 details a method utilizing this product type for floor tile over a wood subfloor. Previously, this was approved for wall installations over wood or metal studs in method W246-05 and for bathtub/shower walls in B425-05.

This is a backerboard constructed from extruded polystyrene and coated with fiberglass mesh and cementitious coating, designed as a substrate for ceramic tile in wet or dry areas. Available in various lengths, this material can be applied over studs and subflooring. Ceramic tile can be bonded to it with dry-set, latex-Portland cement, or epoxies.

Fiber-Reinforced Gypsum Panel Backerboard/Underlayment:
There are two new methods that were approved in the TCNA Handbook on this product type. They are both designed for wall tile installations. Previously, a method for floors was approved over a wood subfloor for this product type. Method W247-05 details an installation on an interior wall over wood or metal studs with dry or limited water exposure. Method B430-05 is for Bathtub walls over dry, well-braced wood studs in dry or limited wet areas.

This product type is designed for use on floors, walls, and ceilings in dry areas. The board is applied directly to wood or metal wall studs or over wood subfloors. Follow the manufacturer's instructions for installation and joint treatment. Manufacturers claiming to provide products of this type include: USG Corporation.

In this product type, it is important to note that the Handbook specifically requires the product to be used in dry or limited wet areas. A limited Water Exposure Area is thusly defined: The surfaces that are subjected to moisture or liquids but do not become soaked or saturated due to the system design or the time exposure. Examples include: residential bathroom floors and foyers, residential bathroom vertical surfaces including tub surrounds without a shower head, and kitchen countertops.

Important note: The definition of a limited water exposure area is consistently debated. With this product category, I strongly urge you to check with the manufacturer warranties and installation instructions, as there is a strong likelihood that despite the fact that the Handbook calls for this limitation, you may be able to get a guarantee that you are comfortable with for interior walls for showers.

It has been stated before that the TCNA Handbook is a guide to be used for consideration of methods and products. There are always going to be products and methods used that deviate from the specification or are not as of yet even in the Handbook. This is when we urge you get these instructions in writing.



DensShield by Georgia Pacific is an example of coated glass mat water resistant gypsum backerboard.
Clearly, current methods regarding the use of Green Gypsum Board and White Gypsum Board in wet areas subject to moisture are strongly advised against. Despite the fact that this is now mostly widely known in the tile industry, we continue to receive calls and reports on problems where the practice is occurring. Excuses we hear allude to the fact that local building codes still cover these products in these areas. Even if this is the case, it is evident that there are five specific product categories covered in this article that are proven to be superior in performance in these applications. When you have such a wide array of quality product choices, why would you continue to subject your company and your customer to liability risk with these products? It just does not make sense.