If you're wondering why you need to include expansion joints when installing tile, you've come to the right place. Let me explain why they are so important.
Tile Installation Expansion Joints Are Critical for Success!
Expansion joints are also known as Movement Joints or Movement Accommodation Joints. In ceramic, porcelain, glass and stone tile installations, they are critical to the success and longevity of the installation.
According to the NTCA (National Tile Contractors Association) Reference Manual, an expansion joint is,
“A joint through the tile, mortar, and reinforcing wire down to the substrate.” By integrating these “stress relievers” into the tile assembly, expansion and contraction takes place without compromising its integrity."
Sadly, they are probably the least used, most misunderstood and yet one of the most important listings in the Tile Council of North America (TCNA) Handbook.
The reason they are so critical is that without them, especially on floors subject to sunlight, most installations which otherwise appear to be well done, will fail.
Without enough room for the tile assembly to expand, the tile will pop up or “tent” most times in the middle of the floor. This situation can occur in both commercial as well as residential jobs, so none of them are exempt from this requirement.
If you are not certain what I mean by tenting tile, here is an unfortunate example. The really sad part of this situation is that the installer did an excellent job… except for the lack of any expansion joints.
To refine the statement I made about a failure review in Flooring Installation Troubleshooting:
"One of the most basic and important facts an installer should know when working with ceramic tile is to always have expansion joints in place. If expansion joints are not part of the installation, failure is lurking in the shadows waiting to strike. On this project, 5,000 sq. ft. of tile was installed on the floor of a public building. An unqualified installer who was a sub to a sub to a sub put the tile in, and he did not install any expansion joints within the body of the tile or around the perimeter. In two places the tile was tented to the point where I could put my hands one on top of the other underneath the tented tiles."
“You have to allow for expansion, whether residential or commercial. Expansion joints are not optional – they are a requirement.”
What the TCNA Handbook Says About Movement Joints
The TCNA Handbook EJ171 Movement Joint Guidelines for Ceramic, Glass and Stone clearly states,
“The architect or designer shall show the specific locations and details of movement joints on project drawings.”
Given this sentence, where does the misunderstanding begin?
Unfortunately, many people involved in the installation of tile products don’t understand that the tile does move. If this expected movement is not accommodated, the tile will become rebellious and most likely will become very expensive to the responsible person or company.
In other words, as a tile installer you are much better off to simply include expansion joints on every project.
The attached Handbook detail EJ171 shows the necessary components of the movement joint:
- Width that is four times the expected movement
- Compressible back-up
- Rounded back-up with no bond to the sealant
- The depth of the sealant is one half of the width of the joint
I call your attention to the sealant. Notice that the elastomeric sealant is attached only on the sides of the two adjacent tiles.
One critical point here is that the sealant does not contact or bond to the sides and/or bottom of the joint. If the sealant is allowed to do so, it is locked in place and will have zero movement ability. In this case, the insertion of a “Rounded Back-Up,” or foam backer rod allows the concrete floor to expand and contract, but its primary role is to keep the sealant where it belongs: attached to the tile only.
Think of the movement of the sealant as an in and out movement like the action of an accordion.
The sealant will also allow the tiles to move in a back and forth motion similar to rubbing two hands together.
Lastly, you will notice that the detail refers to the joint material as sealant. This is done purposely to differentiate it from lesser quality caulking products (acrylic latex or siliconized latex) which dry hard and do not allow for permanent flexibility. According to the requirements of EJ171, this sealant must be 100% silicone, urethane or polysulfide.
If you understand these principles and install the joint properly, you can expect that the expansion joints will permit this required movement to take place, keeping the tile flat on the floor where it belongs.
Certified Tile Installers understand this and can properly install movement accommodation joints.
Still Wondering Why You Need Movement Joints?
If I've not made the point about how critical expansion or movement joints are to ceramic tile installation, please let me know in the comment box below.
If you're still wondering, consider learning more about the Certified Tile Installer program.