Tile Q & A
The Tile Council of America, Inc. (TCA) is delighted to work with Tile Magazine to address questions on tile specifications and installation. Content for future columns will be drawn from questions submitted to firstname.lastname@example.org.
Movement joints are our first topic. We will address issues related to movement joints and where to find specifications.
Why are movement joints needed?
Recognizing that tile is a facade, movement joints are needed to eliminate stresses that can occur between the substrate and the tile due to differing amounts of expansion and contraction.
Where should movement joints be placed?
The TCA Handbook for Ceramic Tile Installation recommends allowing for expansion and contraction in every tile installation. In small rooms, a gap at the perimeter of the room (often hidden by baseboard or shoe molding) is sufficient. For larger areas, the movement joints will be visible.
The TCA Handbook does not specify the exact location nor frequency of movement joints as there are many site related conditions that must be addressed - however, guidelines are given in Detail EJ171 in the TCA Handbook. It is especially important to note for interior installations, movement joints are placed more frequently when moisture or direct sunlight is expected. For exterior installations, the range of temperature from summer highs to winter lows must be considered.
American National Standards Institute's (ANSI) publication on Specifications for the Installation of Ceramic Tile, or ANSI A108/A118/A136.1, references standards for installation and installation products such as backerboards, grouts, and mortar.
ANSI A-3.4.1 states that movement joints are required over all construction, control, and expansion joints in the backing and where backing materials change or change direction including terminations of tilework where it abuts restraining or dissimilar surfaces.
ANSI AN-3.7 discusses requirements for movement joint preparations by other trades.
Why do rooms with more sunlight need more movement joints?
The intent of the guideline regarding sun exposure is to recognize that areas that get warm (or wet) may experience greater amounts of differential expansion. If the areas exposed to sunlight are warmer than surrounding areas, movement joints should be used more frequently. If the tile surface is not appreciably affected, no accommodation is needed in the joint spacing.
Only the area subjected to increased temperature needs to have movement joints more closely placed, not the entire floor if elsewhere the floor is an even temperature.
What other things should be considered when determining spacing for movement joints?
Many things can subject the tile layer to shear forces in addition to temperature and moisture. The following is a partial list:
• Continued curing of the concrete substrate can put the tile in compression
• Deflection and vibration of the substrate - particularly with suspended slabs
• Seismic activity
• Location of weight-bearing columns
From what is a movement joint made?
Movement joints are filled with material that allows for contraction and expansion. For floor applications, urethane, neoprene, or polysulfide are most often used in traffic areas and silicone sometimes where traffic is not a concern.
Traffic areas require a sealant with a Shore A hardness of 35 or greater. Other related issues can be found on the Tile Council's web site (www.tileusa.com) under technical services.
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