If you’ve been reading TileLetter for a while, you’ll notice that in our Ask the Experts section, people query our technical team about issues that come up in a variety of project settings. Sometimes, these questions are pertinent to a topic we have sched- uled for a TileLetter issue, which is the case with this question that relates to large-format tile. A builder inquired: “We have 12˝ x 24˝ and 12˝ x 36˝ tile that weighs about 4 lbs. per sq. ft. We are install- ing on commercial bathroom walls in a brick layout. Is it standard practice or even necessary to put cement backer board up first to ensure the tile stays up? A tile installer said he could just install it right over the gyp board, and I disagree. Please let me know what is regulation or expected for this kind of installation.” Mark Heinlein, NTCA training direc- tor and technical trainer/presenter, fielded the query, helping the builder determine whether the gypsum board is the appropriate choice for this installation. Here is his reply: “The installation of ceramic tile on gypsum board is detailed in TCNA Handbook Method W243. As noted in the “Preparation by Other Trades” section of this method, it is very important that the gypsum board has been installed in accordance with Gypsum Association publication GA-216. “GA-216 (which further refers to GA-214) describes the installation details for gypsum board that is to receive a finished tile installation,” Heinlein continued. “It specifies stud size and placement, fastening sched- ule, board thickness, whether a single or double layer is required and how the joints and fastener heads are to be treated. For example, the face layer joints should be treated with tape and one bedding coat of joint compound (no finish coats) and the fastener heads are to be treated with one coat sponsored by LARGE-FORMAT TILE Turn to TCNA Handbook for guidance in installing large-format tile The installation of ceramic tile on gypsum board is detailed in TCNA Handbook Method W243. 56 TileLetter | September 2017