SCHLUTER SYSTEMS | T08 MTN

KERDI Membrane over Gypsum Wallboard Please see below regarding gypsum as an acceptable substrate for KERDI membrane. From our standpoint as a manufacturer - gypsum is OK. The ultimate decision regarding gypsum wallboard as an acceptable substrate should be made by your local building official. Kindest Regards, Schluter Technical Services Included below is a screenshot from the  Schluter®-Shower System Installation Handbook  listing gypsum wallboard as an approved substrate. The Schluter®-Shower System Installation Handbook detail K-SH-K under Requirements lists: Solid backing - gypsum wallboard, cementitious backer unit, fiber-cement underlayment, fiber-reinforced water-resistant gypsum backerboard/underlayment, coated glass mat water-resistant gypsum backerboard, Portland cement mortar bed, concrete, or masonry. The detail also lists under Solid Backing Materials: Gypsum wallboard - ASTM C1396/C1396M Gypsum wallboard panels must comply with requirements of ASTM C1396.   In addit

When installing Schluter products, dissimilar metals in contact anywhere in the system shall be avoided to eliminate the possibility of a galvanic (re)action or galvanic corrosion. It is the responsibility of the specifier and/or design professional (i.e., architect, designer, or engineer) to determine the compatibility of materials within any given assembly. Nicholas Buccalo posted a nice blog concerning this issue from which the chart was taken below. Click here to read his post dating June 14th, 2017. The Limited Warranty is conditioned and will be considered null and void, and Schluter-Systems will have the right to refuse any claims if the Product(s) have been improperly installed, used in a manner other than that for which the Product(s) were designed, or in any way contrary to the Written Materials. Additionally, Schluter will not be responsible for the performance of any non-Schluter products or workmanship in the installation.

There is no issue installing large format tile on a shower ceiling with KERDI/KERDI-Board provided the structure construction ( i.e.,  joists and wall board on the ceiling) are designed and installed to carry the load.  We state this in the Shower Handbook with the following: "When KERDI/KERDI-DS and tile are installed on the ceiling, the solid backing and fasteners must be able to support the load of the tile and setting and grouting materials." By leaving out any qualifications on the load capacity of KERDI, we are saying there is no issue with the bond of the KERDI to the solid backing, or the tile to the KERDI/KERDI-Board, provided both are installed properly. The stress on the KERDI/KERDI-Board is no different when installing 12"x12"x3/4" vs 2"x2"x3/4" tile.  The following calculation shows this in detail.  The weight of granite is approximately 1lb per cubic inch. This means the total weight of a 48"x48"x3/4" slab would be 17