Tile Tip: Movement Accommodation Joints are Crucial for Success

This inside corner was grouted and then, to meet the job specifications, a very thin layer of 100% silicone sealant was applied on top.

Photo: Scott Carothers.

Sometimes a tile installation can present some real challenges, even for the seasoned veteran. Conversely, some things related to tile work are so simple that you may wonder why difficulty and/or ignorance creeps in. Almost everyone who installs tile knows that movement accommodation joints are crucial for success.

The American National Standards Institute (ANSI) provides the following guidance.

A108.01

3.7.4.1.1 Suitable sealants include silicone, urethane, and polysulfide.
3.7.4.1.2 Tile edges to which the sealant will bond shall be clean and dry.
3.7.4.1.3 Install sealant after tilework and grout are dry. Follow sealant manufacturer’s recommendations.

A108.02-4.4 Movement Joints

4.4.1 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.
4.4.2 Movement joints are a requirement for tilework.
4.4.3 Movement joints shall be kept free and clear of all setting and grouting materials.

The Tile Council of North America (TCNA) Handbook in EJ171 states the following;

Perimeter and field movement joints within a tile installation are essential and required.
Perimeter Joints-movement joints are required where tilework abuts restraining surfaces such as perimeter walls, dissimilar floor finishes, curbs, columns, pipes, ceiling, and where changes occur in backing materials, but not at drain strainers.
Change in plane, interior-movement joints required at all inside corners.
Interior – Perimeter joints, other than perimeter walls-preferred not less than 1/4” but never less than 1/8”
Change in plane-same as grout joint but never less than 1/8”

Given all of this information, it is clear that movement accommodation joints are necessary, but many times these joints are installed incorrectly or not installed at all. The image shows an inside corner that appears to have the required sealant joint installed, but it is cracked. This inside corner was grouted and then, to meet the job specifications, a very thin layer of 100% silicone sealant was applied on top.

Being hard and rigid, the grout is incapable of handling the movement that occurred and the silicone smeared on top was not designed to function in this way. The better choice would be a clean joint filled with a closed-cell foam backer rod and a 100% silicone sealant which will remain flexible and function well for many years.

Some or all of this information may seem complicated and over the top, but it really is not. If the installer carefully reads the information in the ANSI document and the TCNA Handbook along with the manufacturer’s recommendations and understands the importance of allowing movement to take place, the installation will stand the test of time. If not, an unsightly failure occurs which means an unpaid callback for the installer to correct the error.

The cracked inside corner joint has failed to do its job and, even worse, the consumer viewing this situation walks away thinking that if tilework looks like that, “I don’t want it.” Again, the tile installation industry gets another black eye. Think about it.

Scott Carothers is the Director of Certification and Training for the Ceramic Tile Education Foundation headquartered in Pendleton, SC, and is responsible for the creation of the Certified Tile Installer (CTI) program, is involved in the creation of the new Advanced Certifications for Tile Installers (ACT) program as well as providing training to others in the tile industry. He has been involved in the ceramic tile industry for over 33 years and was the owner of a successful retail firm prior to coming to CTEF. He has served as President of the NTCA, Chairman of the NTCA Technical Committee and named the NTCA Tile Person of the Year in 2005. He is a voting member of the ANSI and the TCNA Handbook committees. He may be contacted at 864-222-2131 or scott@tilecareer.com.