It All Moves, Plan For It
During my time in southern California I would mention an article to contractors titled - It All Moves, Plan For It. Most of the time I was preaching to the choir. The majority of the coastal areas of that region are so climate steady that there is not a lot of movement to housing and flooring materials, to where it became an issue. You get into the foothill or mountainous regions and that’s another story.
I’ve been in the Boise, Idaho area for going on 2 years now and have been mentioning this article to contractors quite often. Due to it being so spot-on for this area I asked the author, Dave Gobis (“The Man” in hard surface tile consulting) if I could post it and Dave agreed. So you can all thank Dave Gobis for the following article "It All Moves Plan For It".
Dave is the principal owner at Ceramic Tile Consultant LLC and is a hard surface tile expert so the article is based around that type of flooring. The thing that most folks do not consider is that it applies to so much more than just flooring.
Dave Gobis used to get sent to different countries to inspect and consult on tile installations. He is semi-retired and now just looks at floors within a day's drive from Milwaukee Wisconsin.
Understand that this article was written about 15 years ago and the contact info for Dave within the article is likely not current. Dave is extremely knowledgeable and can be found via LinkedIn. Also, the information quoted from industry standards and guidelines was from 2005 and new documents are published almost annually as to tile installation.
Enjoy the following article.
It All Moves, Plan For It !
By Dave Gobis
© 2005 CTEF
Seems no matter how hard we try to drive home the message, restrained movement of tile installations is a continued problem and regular mode of failure. Tile moves, wood moves, metal moves, it all moves, you can count on it. So, why not plan for it? Today's structures are much more engineered than in the past. Wood structures, in particular, have become highly engineered. Often, they employ many various types of engineered joists and engineered panels that are not fully understood by those installing them. The movement issue is further compounded by the tendency to build structures to minimum code requirements. Add a little fast track construction to the equation, like installing floors with temporary heat or just as the painter is finishing the walls the drywaller installed and taped last week that were barely dry and you have a lot of moisture-induced movement in the structure. That is just about the time they call for the tile installer. So now we have the structure contracting while drying out and taking our tile job with it. Granted, this is a worst-case scenario but one installers see all the time.
Expansion joints, also known as movement accommodation joints, are intentional interruptions in the hard materials making up a tile installation that provide enough space for the materials to expand and contract naturally without causing damage to either the tile installation or the surrounding structure. Today, most of the emphasis on expansion joints is placed on large commercial installations because they are required under the specifications that are part of a contract.
But, the fact is, even small residential floors need at the very least, an expansion joint around the perimeter of the floor. Current study shows that in today’s modern minimum code compliant construction, as opposed to over-engineered structures in the past, they play an ever-increasing role of importance. The 2005 edition of the TCNA Handbook has made several changes to reflect the latest recommendations of the wood and concrete industry. Accepted industry standards recommend that expansion joints be placed:
1. Wherever there is a change in the backing materials (e.g. a plywood subfloor meeting a concrete slab), or where tile work meets or abuts perimeter walls, curbs, columns, pipes, other penetrations or restraining surfaces.
2. Wherever tile work passes over control, expansion, seismic, cold, construction or other structural joints.
3. Every 20 to 25 ft. in both directions for interior tile work not exposed to moisture or direct sunlight.
4. Every 8 to 12 ft. to interior tile exposed to direct sunlight or moisture.
5. Every 8 to 12 ft. in both directions for exterior tile work.
The width of a movement joint varies too, depending upon its interior or exterior location and the temperature differences between summer and winter (interior tile work exposed to direct sunlight should always be treated as exterior). Manufacturers of tile and setting materials, The American National Standards for Ceramic Tile Installation and the Tile Council of North America TCNA Handbook recommend minimum widths must be increased 1/16 in. for each 15°F for the actual temperature range greater than 100°F between summer high and winter low”. Minimums widths are as follows:
Exterior tile work
a. 3/8 in. min. for joints 12 ft. on center.
a. ½ in. min. for joints 16 ft. on center
Interior tile work
a. For quarry, porcelain and all other floor tile, same as grout joint but not less than ¼ in.
b. For glazed wall or ceramic mosaic tile, ¼ in. is preferred but not less than 1/8 in.
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:
On all floor tile installations, there must be a perimeter joint between the last row tile and the enclosing walls. The joint should be a minimum of ¼” and free of any grout, setting material or debris. As with all underlayments, if a backer board abuts the wall it to should have a ¼” gap. There should also be joints located in the center of doorways where tile runs continuously such as a kitchen to a dining room or where an individual room changes direction such as an “L” shape
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 the 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
Columns and Beams
On concrete structures floor tile installations should always be isolated with an expansion joint particularly around columns. Columns and column pads perform a supporting function independent of the floor and must be allowed to move. In wood structures, the tile directly over a beam is solidly supported where the material placed on either side of the beam will deflect a certain degree till it reaches the next area of support. Ideally a joint should be placed over the center of the beam.
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
Making Expansion or Movement Joints
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. Premade 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 3 side bonding, depending on the 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 ¼ in. 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 snugly in the joint to the recommended depth. This prevents the joint from destroying itself when it opens or is compressed by providing only 2-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 as 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.
To use water-based caulks, you simply fill the joint with caulk and then compress it into the joint with a striking tool dipped in water (you may have to clean and re-wet the strike as you go. Clean the excess with a sponge, making several passes until the excess has been removed. It is a good idea to check the caulk joint area to ensure that all the excess has been removed. Applying silicones and urethanes are a bit more challenging. You should really tape the sides of the joint to protect surrounding areas from residue, it makes clean up much easier. When tooling silicones or urethanes, a little soapy water will keep caulk from sticking to the tool used to finish the joint. Remove the tape by pulling it over the top of the joint and protect the area until the caulk has cured. Time will vary with product, some take hours, some days. Whatever brand of sealant or caulk you use, follow all manufacturer’s instructions regarding preparation of the slot, backing, application temperature and humidity, and curing requirements.
When properly made, 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 ¼” 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.
Bio: David M. Gobis, a 3rd generation tile setter, is the Executive Director of the Ceramic Tile Education Foundation. He has been in the trade for over 35 years and owned a successful contracting business for many years prior to his current position. Mr. Gobis is a member of the NTCA Technical Committee and American National Standards ANSI A108, American Society for Testing of Materials C-21 and TCA Handbook committees. He can be reached at firstname.lastname@example.org.