CTEF Tile Tip: Is it an Expansion Joint or Not?
August 27, 2010
Expansion joints in tile work are about as popular as going to the dentist for a root canal. Decorators are not a fan because they have a tendency to interrupt the floor pattern. Tile installers are uneasy because many times the plans don’t definitively indicate the type or location.
The 2010 issue of the TCA Handbook defines an expansion joint in three separate definitions. (1) A separation provided between adjoining parts of a structure to allow movement where expansion is likely to exceed contraction; (2) a separation between pavement slabs on grade, filled with a compressible filler material; (3) an isolation joint intended to allow independent movement between adjoining parts. The Handbook goes on to state that the architect, builder or design professional must specify movement joints and show location and details on drawings.
When the tile installer provides adequate clean and open space around the perimeter of the tile work and the expansion or “soft” joints within that area as detailed, all is well. When these joints are overlooked or dismissed, trouble is lurking in the future which may take years to happen.
It is understood that the tile does move due to structural changes, sunlight and moisture. The installer needs to accommodate that movement and still provide a pleasing appearance. There are numerous manufacturers that produce various types of expansion joint products that are easily installed with thinset mortar. Be sure to have an adequate amount of mortar under the anchoring leg as well as an additional pass with the notched trowel over the top prior to setting the tile. Another technique is to back butter the tile where it meets the strip and press it into position.
The other method of installing expansion joints in the tile assembly is to clean the joint of all setting and grouting materials, place the appropriate rounded compressible back-up into the joint (where required) and apply the specified sealant which may be silicone, urethane or polysulfide.
When expansion joints are properly installed, they work well. When done incorrectly, they don’t. Look at the attached photos. Is it an expansion joint or not? In this case it is not, because it was grouted solid and subsequently cracked.