QUESTION
I understand I need to have expansion joints in my exterior tile installation. My question is how frequently do I need them, and particularly how wide do they need to be? The customer wants an 1/8″ grout joint. Can I make my expansion joints the same size?
ANSWER
Correctly designing and specifying expansion and movement joints for an exterior tile installation is a critical part that will determine the long-term success of the installation.
The Tile Council of North America Handbook for Installation of Ceramic, Glass and Stone Tile includes Method EJ171, which gives guidance for movement accommodation joints. Method EJ171 requires a knowledgeable design professional to specify this part of each tile installation.
The minimum allowable width of an exterior movement accommodation joint is 3/8″ for joints 8′ on center and 1/2″ for joints 12′ on center. Minimum widths must be increased by 1/16″ for every 15 degree Fahrenheit temperature change over 100 degrees from summer high to winter low. An example of this is if an installation can experience a 115 degree Fahrenheit change in a one-year period then an additional 1/16″ of an inch should be added to the minimum width.
Another way to explain this is where the temperature varies up to 100 degrees Fahrenheit, the joints should be no more than 12′ on center based on a 1/2″ width joint. The joint width needs to increase the minimum width by 1/16″ for each 15 degree Fahrenheit temperature change greater than 100 degrees.
For exterior installations, the frequency of movement joints is given as every 8′-12′, dependent on the width of the installed movement joint.
Other factors must also be considered to correctly design the expansion/movement joint for an exterior installation. Please refer to all of the information in TCNA Handbook Method EJ171 for more guidance.
