It All Moves, So Plan For It!
2. Wherever tile work passes over control, expansion, seismic, cold, construction or other structural joints.
3. Every 20 to 25 feet in both directions for interior tile work not exposed to moisture or direct sunlight.
4. Every 8 to 12 feet to interior tile exposed to direct sunlight or moisture.
5. Every 8 to 12 feet in both directions for exterior tile work.
a. 3/8 inch minimum for joints 12 feet on center.
a. 1/2 inch minimum for joints 16 feet on center.
Interior tile work
a. For quarry, porcelain and all other floor tile, same as grout joint but not less than 1/4 inch.
b. For glazed wall or ceramic mosaic tile, 1/4 inch is preferred but not less than 1/8 inch.
Anyone doing tile work should be familiar with the contents of the TCNA Handbook. If not, you can contact the Tile Council of North America for a copy of the newly revised 2005 edition. It is relatively easy to use but upon opening it for the first time, you may find its contents a bit overwhelming. The following is a list of the most common floor locations for installing movement joints:
Different Substrates: When the floor is composed of two different materials such as a concrete slab used to extend an existing wood subfloor, an expansion joint located directly at the split is required to accommodate the different rates of expansion and contraction. Two different materials have two different rates of movement. There is not a single membrane manufacturer who would warrant use of their product in such an application. This holds true for wood construction additions to existing wood structures. Neither backer board nor plywood over the new framing will stop the movement on the new addition.
Concrete Floors: Concrete floor slabs may be produced with cold joints, control joints or expansion joints. Cold joints are cracks that appear when fresh concrete is placed next to an existing slab. Control joints are partial interruptions in a slab that are intentionally placed to direct or channel cracks that will appear either during or after the slab has cured. Control joints can be formed or molded while the concrete is still plastic, or they can be saw-cut after the concrete has sufficiently hardened. Concrete slab expansion joints are produced when two neighboring slabs are separated by a filler strip placed before the concrete is poured. The joints are designed to allow for independent movement of each slab. These "joints" are usually found on commercial installations but they may also be found on residential construction. If tiles are to be applied on these slabs, an expansion joint must be incorporated into the tile portion and must be located directly above the joint in the concrete. They may not be relocated with a membrane.
The right time to discuss the need for joints is at the planning stage so that all other trades involved with the tile installation (concrete or carpentry crews) know precisely where the joints will be located. This means working with the owner, architect or general contractor to ensure that everyone agrees on the location for all construction joints. Constructing field made joints that perform is no easy task. They require a fair amount of skill and can be very time consuming. Pre-made joints can become very desirable for this reason and you will find in many instances they are less costly. A movement joint is an open slot that extends from the top of the tile. A compressible filler, backer rod, or bond breaker tape is often used to prevent three-side bonding, depending on specific application. This is followed by a bead of sealant or caulk. A movement joint located around the perimeter of a floor tile installation is the easiest to make. You simply hold the tiles at least 1/4 inch away from the wall and apply caulk or sealant if needed. Usually the perimeter of the floor is then finished with a baseboard of tile, wood or other material that masks the expansion joint. If not the customer should be made aware that the joints will not resemble a grout joint. For control joints, the layout of the tiles must place the grout joint directly above any construction joints. As this is rarely practical, a membrane is often used to relocate the positioning of the joint. If a membrane is employed, some will allow for relocation of all but true expansion joints to the next full grout joint. Visible joints ideally should mimic the appearance of the grouted joints so they do not detract from the appearance of the finished installation. To make these joints function properly, they need another element called backer rod. Backer rod has a round cross-section, is available on spools and is placed snuggly in the joint to the recommended depth. This prevents the joint from destroying itself when it opens or is compressed by providing only two-sided adhesion. Backer rod is hard to find in stores, but easy to find on the Web. Because it can make the difference between a joint that lasts and one that fails, it is worth searching for.
Choosing and Installing
the Caulk or Sealant
Sometimes a compromise has to be made when selecting a material to place in the movement joint. As this critical part of every tile installation is often ignored, there is not an overwhelming choice of color when it comes to sealants. Sealants typically have a short shelf life and are three to four times the cost of regular caulks. Caulk is an all-purpose term and often used to describe sealants. Most often the terms are used interchangeably, and the products serve the same purpose: to fill gaps and allow movement between building materials while keeping water and soil at bay. Many times the approach taken is to select durable sealants for heavy-duty service applications. Silicone stands up to extremes of moisture and temperature, cures soft, and remains flexible. Silicone is inorganic, it is unaffected by UV radiation and many resist mold and mildew. Silicone can be applied at virtually any temperature and can stand up to adverse conditions shortly after application. Polyurethanes sealants can stand up to abrasion and remain flexible and weather resistant. For regular duty installations (residential applications), you often must sacrifice durability for invisibility and select a sealant or caulk that closely matches the grout joint. Water-cleanable caulks are available to match most grout colors (some are even available sanded to match the texture of grout) These may require more frequent replacement than the other types, but are worth the additional effort and expense if seamless good looks are important.
When properly made and finished, movement joints provide service for many years. However, because expansion joints move and flex and get abraded and torn, they will eventually wear out. Sometimes, the entire system of joints may need replacement while at other times, only a spot repair is needed. It is wise to make the owner aware that replacement or repair is a maintenance item, not a failure. I would also like to acknowledge I understand the difference between real world and perfect world. In the perfect world, every job would have joints as needed using proper materials. In the real world, there is nothing harder than selling a caulk joint down the middle of someone's dream floor. Likewise, most are very adverse to having joints in doorways or leaving the perimeter of the room with a 1/4-inch gap. All I can say is at that point it becomes a business decision. That the floor is going to move for any number of reasons is a given. Not putting the joints in is a risk. Many get by for numerous years and never have a problem; others are not so fortunate. You make the call.