Ceramic and porcelain tiles are as beautiful as they are functional, but they are very greedy when it comes to the space needed around them to absorb any movement. Many people don’t understand that when a surface such as a tile floor becomes warm or hot to the touch from direct sunlight or in-floor heating, they grow larger or expand. Allowing little or no room for the tile assembly to expand can cause the tile to pop up or “tent” in the middle of the floor. This situation occurs in both commercial as well as residential jobs, so none of them are exempt from this requirement.
This expansive growth must be accommodated with shock absorber-like areas known as expansion or movement accommodation joints. Since grout joints do not offer any movement absorbing qualities, these joints must be filled with a resilient material such as 100% silicone, urethane, of polysulfide. The Tile Council of North America (TCNA) Handbook, in section EJ171, clearly shows the shape, size, and location of these shock absorbers.
Once the type, size, and frequency of the expansion or soft joint are determined, the installation is easily completed. The joint must be free of any grout or mortar and completely dry. The detail may call for a foam backer rod to be placed in the bottom of the joint, but in many applications (such as over a concrete slab or backer board) a generic joint may be necessary.
A bond breaker tape should be installed at the bottom of the joint to keep the sealant from bonding to the surface below. This product can most times be difficult to find. An easy and inexpensive alternative is to sprinkle a small amount of granular material such as dry sand, thin set or grout into the joint. Be certain that any excess material is cleaned off the surface before the sealant is applied.
Apply the proper sealant (no acrylic latex or siliconized caulking) using a caulking gun. Carefully fill the joint completely. The next step is really critical to a successful installation. Using a pump sprayer filled with a small amount of dish washing detergent and water, liberally coat the sealant and the tile surface. Smooth the sealant with a sealant tool or a plastic spoon, as shown in the photo. The sealant will not stick to the tile, but will stay on the spoon until the joint is completed.
Allow the sealant to dry overnight, then wash the area with a wet sponge until the soap residue is gone. Congratulations! You have installed a professional-looking and long-lasting expansion joint.
