What is a Non-Linear Expansion Joint?
When the topic of expansion joints is discussed, it many times causes confusion. Are they required? Who is responsible to design them? How are they to be installed and how often do they repeat? The questions need to be answered before installing any expansion joints.
EJ171 of the TCNA Handbook makes this statement, “Perimeter and field movement joints within a tile installation are essential and required.” ANSI A108.02-4.4.2 further states, “Movement joints are a requirement for tilework” followed by this note, (See A108.01-3.7) which fully describes the parameters of all tilework expansion joints.
The Handbook also states: “The design professional or engineer shall show the specific locations and details of movement joints on project drawings.” This means that the installer should not design, detail, or locate an expansion joint, ever! It is not your job, so don’t accept the responsibility.
For our discussion here, we will focus on a rather new addition to the ANSI book known as non-linear movement joints. Under ANSI A108.01-3.7.5, it states, “non-linear movement joints: 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-tooth, 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 specifications. The intended application must be approved by the sealant manufacturer, and the sealant must be properly installed per the sealant manufacturers’ requirements. (See Figure 11.0)”.
The approved sealants include silicone (100%), urethane, or polysulfide. Acrylic latex or siliconized latex caulking does not meet the requirement for remaining flexible and should not be used.
The Handbook sets size requirements for generic movement joints which are subject to direct sunlight or moisture. In quarry tile installations, the sealant joint should be the same size as the grout joint, but not less than ¼". For all other tile, the preferred sealant joint size is preferred at ¼", but never less than &frac;18".
Interior tilework exposed to direct sunlight (heat) or moisture require expansion joints at a maximum of 12' in each direction. When the installed tile includes a straight grout joint, meeting the 12' requirement is usually not a problem. However, when rectangular tiles such as 12" x 24" or wood-look planks are installed at a 33% offset, the above requirement can be difficult to achieve. But now that non-linear joints are acceptable, the tile installer’s job is much easier.
As you can see in the attached photo of a rectangular tile pattern (which follows Figure 11.0 in the ANSI book) that is subject to sunlight, the non-linear expansion (soft) joint can easily be installed. The beauty of this new joint procedure is that the previous requirement which called for cutting tiles in a straight line to meet the 12’ on center rule are eliminated. Done correctly, they look great and function well.
Use this on your next job and sleep well at night knowing that you have followed industry guidelines and know that failure is eliminated.