MAPEITechTip: What are movements joints and why are they important in a tile/stone/glass installation?

Since all tile/stone/glass installation systems are made up of multiple layers (eg: substrate, surface preparation products, bond coat, finished covering and grout) each layer reacts differently to thermal changes within the installation environment.  Typically the greater the ‘swing’ in temperature (ie: even interior sun rooms or enclosed patios exposed to sunlight and thermal heating) moisture and deflection the more the layering system must be able to accommodate for this movement without failure (tenting or de-bonding) during the life-cycle of the installation.

The term ‘Movement Joints’ which is a broad term under TCNA EJ171 encompasses (11) different types of perimeter and field movement joints.  Due to the fact that each project is different, both structurally and jobsite conditions, the design professional determines the proper placement of these joints within the installation. These joints are filled with an elastomeric sealant that complies with ASTM C920, in place of hard grout, to accommodate this movement.  Always check with the sealant manufacturer to ensure that the sealant is rated for the installation environment, ie: ‘T rating’ for joints subjected to pedestrian and vehiclular traffic.