Tiling Expansion Joints Essentials.

"The tiles in my floor have loosened and tented." Close inspection often shows that when tenting occurs more than one area of tiles has separated from the subfloor or "delaminated". The tiles may not have lifted or cracked but are now loose. The floor will sound “hollow” instead of solid.   There are several reasons why a tile floor might delaminate: the floor might not have been cleaned prior to tile installation; the setting mortar might have partially dried before the tiles were placed in it; the tiles themselves might have had dust or other contaminants on their backs. The most common reason that tiled floors delaminate and tent, is a lack of movement accommodation. Ceramic tile has a different rate of expansion and contraction (coefficient of expansion) than does concrete, for example, a material that ceramic tiles are often installed directly upon. Other common tiling substrates will also expand and contract differently than ceramic tiles. It's important to realize that everything expands and contracts constantly.. All subfloors move but concrete expands and contracts to a greater degree than most. The difference between concrete’s rate of expansion (and contraction) and that of ceramic tile is about 10 to 1. A concrete slab thirty metres across can expand and contract by well over a centimetre. It only takes a fraction of that movement to cause a tile floor to delaminate. Knowing this, tile setters create breaks in tiled floors to accommodate that movement. Soft “movement joints” at specified intervals will effectively divide large tiled surfaces into smaller expanses and thus lessen the effect of subfloor movement. The joints are then filled with flexible material or a commercial expansion strip instead of grout.      In addition to movement joints in the tiled field, perimeter movement joints are used where tile floors are against impediments to movement like walls, columns and cabinets. Whereas smaller tiled floors may not need movement joints in the field of tile, all tile floors need perimeter movement joints, and it is the lack of perimeter joints that most often contributes the greatest force although other factors like contaminants, skinned over setting mortar and other installer errors may also be a factor. Perimeter joints should be at least 6mm wide. In small rooms, a gap at the perimeter of the room (often hidden by the skirting) is sufficient. For larger areas, the movement joints will be visible. The spacing of joints should be calculated for each situation but as a rule of thumb there should be an expansion joint at least every 5m indoors and 3m outside. Areas that get warm (or wet) may experience greater amounts of differential expansion. If the areas exposed to sunlight are warmer than surrounding areas, movement joints should be used more frequently. This will be the case in very sunny rooms. For the key requirements common to all tiling situations, refer to the SABS 0107:1996, Code of Practice for the Design and Installation of Ceramic Tiling. Properly installed tile floors will last virtually forever. Movement and expansion joints help assure that they do. Contact us with any enquiries about tiles.