Backerboards: Evolving Technology since 1968
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.
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.
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.
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.
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.
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.
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.