Multi-level buildings, metal walkways and suspended slabs. What do they all have in common? As there is no ground supporting them, they are prone to various types of movements. These include building movement as a result of settlement, vibration, deflection, loading, etc as well as thermal and moisture movements.
Even ground level surfaces, with basement or parking levels below, should be considered as suspended slabs. Tiling on these surfaces requires a specialist system, to allow for movement in the tiling installation and prevent cracking of the tiles.
In general, all suspended surfaces should have a modified tile adhesive and grout system, while others may require additional care. These include:
Tiling on upper floors that have large windows, which cause thermal fluctuations (expansion and contraction) from the sun shining in. This could also include multi-storey offices or car dealerships with underground parking or workshops.
Suspended walkways and staircases, especially metal staircases.
“Link” bridges, joining different buildings or structures.
Tiling to lift floors would also need the same care, due to the vibrations of the lifts’ operation translating to the floor of the lift-cab interior.
Timber floors, which are prone to various types of movements.
Tiles are by nature rigid, so movement in the substrate causes stress to build up. The use of a tile adhesive that is more deformable is therefore recommended. Alternatively, modifying the tile adhesive, and tile grout with an additive, either latex- or polymer-based, improves the bond strength of the product and provides flexibility for the installation.
It should however be noted that whilst modified adhesive and grout systems will allow for more movement in the installation, the tile itself remains a rigid entity, and excessive vibration or deflection movement may still result in cracking of tiles over time. The use of smaller format tiles rather than large format tiles is advocated in certain installations as, with a smaller number of joints between large format tiles compared with the same area of normal format tiling, less stress (movement) can be accommodated at tile joints.
It is a known fact that the lack of, or incorrectly constructed, tile panel movement joints and perimeter joints is a major cause of tiling failure, and none more so than on suspended surfaces where deflection and movement in the background are more pronounced. These key factors apply for high-risk areas:
Tile panel movement joints should be placed at closer centres, to reduce stress on the installation and to limit damage if a flooring failure occurs.
Movement joints should also be located around the perimeter of all floors, in all vertical corners, against obstructions fixed to the structural background and over all discontinuities in building materials, e.g., at interfaces of concrete and brickwork.
Additional movement joints should be located around any fixtures protruding through the tiled surface, such as columns or stairs.
All structural expansion joints in the background should be respected, and extended through the tiles to the surface, at full width.
Planning for movement joints in the design stage ensures that these will not be placed in heavy-traffic areas, spoiling the visual effect of the tiles.
Movement joints should be filled and sealed with a suitable backing cord/tape and good quality resilient joint sealant material. It is essential that the joint sealant materials bonds only to the edges of the joint (sides of tiles).
Tiling on suspended surfaces requires additional care and specialist products to ensure a durable installation. Planning for these during the design phase reduces downstream delays and possible flooring failures. A wealth of knowledge and experience is available from tile adhesive manufacturers, who can advise on a fit-for-purpose adhesive system and assist with the planning of movement joints for suspended surfaces and other high-risk tiling applications.