ASK THE EXPERTS QUESTION I want to install porcelain tile in my kitchen and my condo association requires a 1/4” cork underlayment for sound mitiga- tion, but my installer and every- one else I’ve spoken with tells me I shouldn’t use cork in a wet area. One installer told me that the NTCA does not recognize 1/4” cork as a suitable substrate for tile applications. Can you tell me if that’s true and, if so, is there some documentation about this that I can present to my condo association? ANSWER In the NTCA Reference Manual, cork is listed as a questionable substrate for tile. There are several other bonded sound-reduction membranes that are designed specifically for tile installations. Bonded sound reduction membranes may be trowel-applied, sheet, or composite membranes that are bonded to a suitable substrate so that tile can be bonded directly to the membrane. Their purpose is to reduce floor impact noise. Material specifications for these products are contained in ANSI 118.13. I suggest finding a substitute for the cork that meets ANSI 118.13. Take the technical data from that product and pres- ent it to your condo association for approval. I hope this helps. – Robb Roderick, NTCA Technical Trainer/ Presenter QUESTION Can you please tell me what the tolerance for lippage for 6”x 36” plank tile would be? The builder is quoting 1/8” which they said is the thickness of two quarters. The tile seems good the long way but the short way – walking across in your bare feet – you feel it. ANSWER The American National Standard Specification for the Installation of Ceramic Tile (ANSI A108) defines acceptable lippage for Pressed Floor and Porcelain Tile that meets the specifications for ceramic tile (found in ANSI Sponsored by 18 TileLetter | November 2017