Seven New Handbook Methods for 2007
WHAT IS METHOD F128?Using this new method, installation of tile over a concrete slab can occur as early as 14 days after the concrete pour using an uncoupling membrane. The uncoupling membrane compensates for the continuing shrinkage of the slab, which otherwise dictates the long-established industry standard cure time of 28 days. This method, aimed at those on “fast-track” schedules, requires that the slab is free of bond breakers and standing water (as do all concrete subfloor methods). Various highly modified thinsets and specific membranes claim similar performance but this is the first time a system has been so identified in the Handbook.
WHAT IS SPOT-BONDING EPOXY?This type of epoxy has “medium-bed” qualities that help the installer achieve a flat tile wall, despite flatness variations in the substrate, which is particularly useful when using large-format tile. Two new methods allow the installation of wall tile by “spot-bonding” it with an epoxy that is recommended by the manufacturer for this type of application. The manufacturer must also provide the minimum amount of coverage required, however, this percentage will be much lower than the thin-set coverage minimum of 80 percent in dry areas.
WHAT ARE METHODS W244E, W244C, and W244F?Method W244E derives from Method W244, which detailed the interior use of cement board or fiber-cement board over studs. In W244E, the “E” stands for “exterior,” and this new method details the exterior use of cement board over wood or metal studs. The Method requires the use of a Type A cement board, versus Type B, which is suitable for interior use only. Also, the assembly requires a water-resistive barrier, per building code. This could be installed behind the cement board or applied to the front of the cement board, so specifiers must check local requirements before selecting.
For interior installations, Method W244 has been split into two separate methods: W244C, where “C” refers to cement board and W244F, where “F” refers to fiber-cement board.
WHAT IS METHOD B431?Method B431 details the use of fiber-reinforced, water-resistant gypsum backer board in wet areas. In a shower-receptor or tub-shower application, this board should not sit in water; that means the board should be installed above the shower mortar bed or up off the tub, similarly to several other boards. Additionally, a vapor membrane should not be used behind this type of board. Because this type of backer board was previously approved for use in dry areas only, other details incorporating fiber-reinforced, water-resistant gypsum backer board have been changed to reflect its new uses.
WHAT ARE METHODS RH112 and RH123?These new methods detail the use of a cementitious self-leveling underlayment in combination with a hydronic heat system, which is embedded in the self-leveler, over concrete (RH112) or wood subflooring (RH123). This type of self-leveler must be poured to a minimum height of 1/2" over the tubing.
WHAT OTHER CHANGES HAVE BEEN MADE TO THE TCNA HANDBOOK?In addition to these seven new methods, the Handbook Committee made numerous language changes and clarifications in the interest of making the Handbook a more user-friendly document. For example, while the tolerance for sub-surfaces installed by other trades was not changed, the existing requirement of 1/16" in 1 foot, and no more than 1/32" between adjoining edges, where applicable, was added to the Preparation by Other Trades section of each applicable method. Previously, this language was only found in the NOTES/DEFINITIONS section in the front of the book, with the methods themselves carrying only the 1/4" in 10 feet language.
Similarly, while deflection requirements have not changed per se, deflection language was changed to incorporate the concept that the floor system must not only conform to the appropriate building codes (IRC for residential and IBC for commercial), but must also take into account the intended use of the installation with respect to expected live, dead, impact, and concentrated loads. An upcoming Tile Q&A article will discuss this change more thoroughly. To locate all Handbook sections that received changes, look for the “07” graphic.