In the past, movement accommodation joints in the substrate, more commonly known as expansion joints, had to be honored and this is still true. Additionally, interior installations subject to sunlight (heat) or moisture called for these joints to be placed a maximum of every 12 ft. in each direction, but they had to be in a straight line. Enter the new standard of the day: 12-by-24-in. rectangular tile—and we have a problem.
How can this tile be installed at the industry-recommended 33% offset and still provide for the expected movement? The method in the past was to cut the tile in a straight line, filling the joint with 100% silicone, urethane or polysulfide sealant which worked very effectively. Unfortunately the pattern was interrupted, leading many designers and consumers to resist this situation saying, “I don’t want my beautiful pattern to be destroyed by those ugly joints. Not on my watch!” When this scenario was followed, the installer was at a greater risk for the installation to fail, possibly resulting in tented tile.
But help has arrived. According to the March 2017 American National Standards Institute (ANSI) specifications, new expansion joint patterns have been approved which allow formerly straight joints to follow the new non-linear joint configurations as seen in the attached photo (33% offset).
ANSI A108.01 – 3.7.5 Non-linear movement joints states, “Generic movement joints, or field joints not over an existing expansion joint in the subfloor or wall, can be installed in a non-linear configuration resulting from the use of tile patterns (e.g. saw-toothed, zipper, etc.). The movement joint must be a properly designed generic movement joint per TCNA EJ171, and the sealant shall meet ASTM C920, or as indicated in the project specification. The intended application must be approved by the sealant manufacturer, and the sealant must be properly installed per the sealant manufacturers’ requirements.”
This is a win-win situation for all involved. The installer gets the expansion joint he or she needs to handle the movement caused by sunlight or moisture, while the designer and/or consumer get the pattern they wanted. Wouldn’t it be nice if everything were this easy?