QUESTION
What are the Industry Standards for Thin-set Contact for Adhered Tile Applications? - In several different articles authored by Mr. Pompo, there are references to industry guidelines and standards for proper installation. One in particular involves the 80% and 95% contact rules and "no voids greater than 2 square inches and full thin-set at all tile edges and corners." I have seen the reference to the 80 and 95% coverage rules in ANSI A108, but I have not been able to locate the specific reference to the 2 square inches and the edge conditions - can you please direct me to that section of the standards?ANSWER
ANSWER - The reference standards for thin-set contact can be found as follows:2013.1 ANSI A108.5-3.3.3 states ...coverage with the corners and edges fully supported.
2014 TCNA Handbook - substrate requirements - Mortar and Mortar coverage page 35 states:
• Ceramic Tile - Average contact area for dry areas is 80% and for wet areas 95%. Mortar coverage is to be evenly distributed to fully support edges and corners.
• Stone Tile - .... minimum coverage is 95% with not voids exceeding 2 square inches and no voids within 2" of tile corners. All corners and edges of the stone tiles must be fully supported....
ASTM C1242-12aE1 Stone Attachments says ...4" wide perimeter of tile is 100% bonded, balance of area must have 95% contact.