About The Case for Expansion Joints
All tile installations require expansion joints – no exceptions. Ceramic tile, porcelain tile, stone tile, glass tile and concrete tile installations need expansion joints to compensate for natural movement that occurs within tile assemblies. That’s why they’re also called movement joints. The reason why movement joints are required is because tile will expand when it’s subjected to any kind of moisture – water or even humidity – or when it is subjected to heat. Tile will contract when it dries or cools. There are also dynamic structural movements that tiles are subjected to that cause them to move. Each day tile installations constantly go through expansion, contraction and dynamic movement cycles, and that’s why it’s so important to design them with expansion/ movement joints.
If you don’t install movement joints within your tile work, then expansion and contraction cycles cause stress to tile assemblies that can result in a number of different problems. If the tiles are well bonded, but lack expansion joints, then the problem might manifest as cracking in the tile or grout. If tile is not well bonded to its substrate then the lack of movement joints may cause the tiles to tent (lift up within areas of the floor, without the grout coming loose). Cracks in interior wet or exterior areas can cause moisture migration that can cause additional damages to adjacent materials. When tile installation failures occur, they’re usually caused by not one, but by a number of compounding factors. In general, and more often than not, the lack of movement joints is a contributing factor to many types of failures.
An expansion joint is a type of movement joint. Expansion joints continue through the tile setting and the substrate. There are construction/contraction/control movement joints, which are movement joints within the tile work above a control joint in the concrete slab. The control joint can either be saw cut, formed or tooled into the concrete slab. There are perimeter movement joints that allow tiles to expand when butting up to a wall or other restraining surfaces. In thin-set applications there are generic movement joints that are only within the tile assembly and not in the substrate below. These are used in cases where the tile substrate requires less movement joints than the tile assembly does. Tile Council of North American Handbook provides all of this information in their EJ171 Movement Joint Guidelines.
The current standard requirement for tile installations is that movement joints are to be installed every 8′ to 12′ for exterior areas, or interior areas where tile work is exposed to direct sunlight or moisture, or for above-ground concrete slabs. For interior areas the standard is every 20′ to 25′. In addition, all tile perimeter and transition areas should have movement joints. That includes all floor and wall applications. This means that inside and outside wall corners in showers are to be movement joints.
The industry standards require that the sealant (caulking) that’s used to caulk movement joints must meet ASTM C920. These sealants are silicones, urethanes and polysulfides. Although they are easier to install, this does not include siliconized sealants, acrylic sealants or latex sealants because they do not perform well. ASTM C920 sealants last a very long time, perform very well and have warranties, unlike the other sealants mentioned.
If you do not install movement joints in your tile work you become liable for any resulting problems even if the problem doesn’t directly relate to the lack of movement joints. It is the architect’s or engineer’s responsibility to specify the type and locations of movement joints. Follow EJ171 requirements if there is no architect or engineer on your project. If you are told not to install movement joints, then ask for that directive in writing. Make sure your client understands that industry standards require them and if left out, you will not be responsible for any resultant damages.