Outdoor Tile Expansion Joints

Why You Need Them in Your Patio

Tile patio with table and chairs.

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After installation, outdoor tiles move. It sounds like a strange concept that a solid material, installed with a cement product, is going to move. Well, it may sound strange, but it is also true. Outdoor tile and the materials used to install it expand and contract, just like wood and other building materials. This movement may be unnoticeable to the eye, but its effects can be quite dramatic. The proper steps must be taken to control the movement so that your beautiful new tile patio will stand the test of time. Thus the need for expansion joints (which are also known as "movement joints").

What Expansion Joints Are and Why You Should Use Them

Expansion joints are spaces between tiles that, instead of being filled with grout, are filled with a flexible sealant. The type of sealant (also called the "caulk" or "caulking") chosen must be weather-resistant. Moreover, if you expect to be subjecting your patio to a lot of traffic, you must select a sealant designed to hold up to foot traffic. Note that even indoor tiling projects require the use of these joints.

The elements can take their toll on pieces of tile used outdoors. These elements include direct sunlight, freezing temperatures, and snow and rain. All of these conditions can cause outdoor tile to move, and you need to allow room for it to do so. If the outdoor tile does not have room to move, it will make room. Grout will crack. Outdoor tiles will pop themselves up off the concrete slab. Entire installations can be ruined because of a lack of expansion joints.

Outdoor tile expansion joints are a small but necessary step when building an outdoor tile patio that you expect to last for many years.

Where to Place Outdoor Tile Expansion Joints 

Placement of expansion joints is very important. According to the Tile Council of North America, a body that helps set standards for tile installations, when installing outdoor tile, there must be an expansion joint every 8 feet to 12 feet, in each direction. It is recommended that you err on the side of caution and use the smaller measurement. So, for example, if your patio were 16 feet by 16 feet, you would have two expansion joints, each running down the middle of the patio and intersecting in the center. Instead of grouting these joints like all of the rest, you would fill these joints with caulk. You can buy caulk that matches the color of your grout at most home improvement stores.

If there are joints in the concrete slab under the tile, there needs to be an expansion joint in the concrete slab, as well. Otherwise, the movement that those joints allow in the slab could carry up into the tile and compromise your installation. Make a note of where your outdoor tile expansion joints will go when doing the patio layout.

The Caulk and Caulking Gun

Commonly used caulking materials for expansion joints are silicone and polyurethane. Do not confuse silicone with silicon. That latter is a chemical element. The former is a polymer (large molecule made up of numerous repeating subunits) comprised partly of silicon but also having carbon and hydrogen in it. Polyurethane is also a polymer; its units are held together by carbamate links. Of the two, however, silicone holds up better to sunlight.

The silicone or polyurethane caulking materials that you will be buying for your project come in cylindrical tubes. But it would be hard to extract the caulk from the tubes without using a tool that exists specifically for this purpose. The tool is called a "caulking gun." Different kinds of caulking guns are available, and they vary in:

  • Durability
  • Features
  • Cost

If you want durability, buy a caulking gun made of a high-quality metal, not one made of stamped metal. The latter can easily get bent out of shape. Despite how basic the caulking gun is as a tool, one model can even have different features than another. For example, how it holds the cylindrical tube can vary. Some have an enclosed unit called a "cradle" that the tube fits snugly into. In others, "rails" are supposed to keep the tube in place, but they do not perform this task as well as a cradle does. If you have a small job to do and will never be using a caulking gun again, there is always the option of choosing the least expensive product so as to stay within budget for this year's yard projects.