Movement stress whether due to thermal or moisture movement, shrinkage, freezing, or dynamic structural movements, tile and stone installations are subjected to them all.
The BS Standards state: Movement joints Stresses in wall and floor tile installations should be controlled by incorporating adequate movement joints. Unless recommendations specific to tiling in specific conditions are given in this part of BS 5385 for materials, design and location of the movement joints, reference should be made to one of the following: floor tiling: BS 5385-3.
Movement joints must be installed in certain areas and positions to prevent tiles or grout from cracking…and in some cases prevent the tiles from tenting and becoming debonded from the substrate. A movement joint is the interruption of the surface to allow for movement.
A ‘movement joint’ is a general term used for all types of joints seen in construction materials that control and allow movement. Most commonly, they are known as ‘expansion’ or ‘control’ joints, but there are various categories. Generally, they contain an appropriate pliable sealant for the intended application, which is often referred to as a ‘soft’ joint.
Movement joints allow for the material in which they are placed to move without restraint; they control where the movement manifests to avoid random cracking in finish materials. An example would be the joints or separations in a concrete sidewalk. If there were no movement joints in the concrete sidewalk, then it would crack at a random point as it is subjected to shrinkage during curing. Rising temperatures cause expansion, lowering temperatures cause contraction, and wet freezing conditions cause both, as the temperature drops and the moisture freezes. Movement joints are also designed to isolate different materials from each other so they do not affect adjacent materials.
More often than not, when there is a tile (e.g. ceramic, porcelain, stone, or glass) failure, a contributing factor is the lack of properly installed movement joints. In some cases, the failure could have been avoided, or damage limited, if there had been proper movement joints. Just like concrete sidewalks, slabs, and bridges, tile and stone need to have movement joints to control the anticipated movements within a structure and the various climatic conditions it will be subjected to throughout the years.
Where the portion of the floor was tented (i.e. lifted and Cracked) inside the front and back doors the lack of a suitable movement joint is visible. In effect, this is what happens to tile floors when they tent, they are constrained at their perimeters with no movement relief, the tile comes under enormous stress as it expands and contracts for one reason or another.
Well-bonded tile floors tend to crack to relieve the stress rather than lose their hold. Properly placed movement joints allow the tile to move and control where the movement manifests (i.e. within the joint where the tile is not restrained).
Ardex and BAL have a full range of Sealants suitable for use in Perimeter and in areas where a soft movement joint can be used. These Silicone are available in Colours to match our most popular Grouts.
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Contact your local representative for more information.