manufacturer before installing thinner (3.5-4.9mm) tiles/panels on a floor. Regarding use of a sound damp- ing product under GPTP - ANSI A108.19 Section 3.0 (Existing Surfaces/Substrates) states in sub- paragraph 3.3 “Do not install over unstable, compressible surface materials or coatings.” I suggest contacting the sound reduction membrane manufacturer for more specific information for use of their product with GPTP. Proper substrate preparation and selection and use of membranes and mortar and trowel and instal- lation techniques are very critical for the successful installation of GPTP. Proper training for instal- lation of this product is required by the A137.3/A108.19 standard. NTCA and product manufacturers provide this training for persons who will be specifying and install- ing the material. In summary, the specification should be very clear in referencing all industry stan- dards for installation of GPTP. The GPTP and setting material manu- facturers should provide you with a clear jobsite-specific warranty and installation instructions for use of their product(s). The install- ers are required to have training. If this is not the case, you will want to carefully consider your accep- tance of risk with this installation. If the manufacturer cannot pro- vide you a clear warranty, I would consider that a red flag. I hope this helps. – Mark Heinlein, NTCA Training Director, NTCA Technical Trainer ASK THE EXPERTS –––––––––––––––––––––––––––––––––––––––––––––––––––– National Tile Contractors Association 626 Lakeland East Drive | Jackson, MS 39232 PO Box 13629 | Jackson, MS 39236-3629 601.939.2071 | 601.932.6117 fax | tile-assn.com The VOICE of the TILE CONTRACTOR The NTCA Reference Manual was devel- oped to identify recurring challenges to successful installations of tile and stone, recognize potential problems,and to gain consensus from industry experts on offering solutions. Now available for purchase in print or digital download.www.tile-assn.com 24 TileLetter | October 2018