After installation, outdoor tiles move. It sounds like a strange concept: 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 patio will stand the test of time.
Thus the need for expansion joints (which are also known as "movement joints").
What Are Expansion Joints and Why Should You Use Them?
Expansion joints are spaces between tiles that, instead of being filled with grout, are filled with a flexible sealant, like silicone or urethane. The type of sealant 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.
Nature can take its toll on pieces of tile. Direct sunlight, freezing temperatures, 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.
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 using 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, using a caulking gun. 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 tile 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.
Outdoor tile expansion joints are a small but necessary step when building an outdoor tile patio that you expect to last for many years. By the way, even when building concrete patios you need to use control joints.