BS 5385-4:2009 pdf free download – Wall and floor tiling一 Part 4: Design and installation of ceramic and mosaic tiling in special conditions一 Code of practice.
5.1 General
NOTE Stresses could be created in the tiling system as a result of movement due to factors such as drying shrinkage (see 5.2) and moisture movement (see 5.3) in the background and thermal and moisture changes in the tiling. These stresses, if not properly controlled, can sometimes be sufficient to promote loss of adhesion and bulging or cracking of the tiling. There are also sources of movement external to the tiling system that might affect the tiles themselves, e.g. settlement and subsidence of buildings, vibration and lift shafts and machinery. Settlement, subsidence and vibration are uncommon sources of trouble, but where the stresses they promote are considerable, wall and floor tiling are likely to be affected.
No precautions can be taken at the time of tiling to eliminate the effects of settlement and subsidence but the use of a deformable adhesive can be beneficial in reducing the effects of vibration and specialist advice should be sought. With other sources of movement, there are positive steps that should be taken to reduce the risk of tiles being damaged during their service life.
5.2 Drying shrinkage movement
Drying shrinkage movement of backgrounds is the most common source of movement in tile installations and it is important that new constructions should be allowed to dry out before tiles are fixed. Minimum drying times in accordance with BS 5385-1, BS 5385-2 and BS 5385-3 should be followed. The times given might require considerable extension depending on the site conditions, thickness and mass of the structure. Longer drying times are recommended for concrete pools and tanks (see 7.3.2).
5.3 Moisture movement
NOTE Porous materials can absorb moisture from the atmosphere and might expand as a result. Conversely, some porous materials contract when they dry out. When these changes are small they do not create problems; but if the size changes are appreciable and ceramic tiles are fixed to such backgrounds, the tiling will be subjected to stress and some loss of adhesion or cracking can result.
5.3.1 Walls
Backgrounds of porous materials having appreciable moisture movements should be thoroughly dry before fixing commences. If these backgrounds are rendered or plastered at least a further two weeks and four weeks respectively should be allowed for further drying.
It is essential that movement joints be provided where necessary according to the guidance given in 5.7 and 6.6.
The walls of premises that are closed for appreciable periods in winter and have no space heating might become damp and expand. In extreme conditions such premises are liable to frost damage and should have provision for automatic heating.
5.3.2 Floors
Moisture movement is unlikely to be a factor in floors of concrete or screeded concrete construction. It assumes greater importance where the base is of timber construction. Timber sub floors prone to distortion as a consequence of moisture absorption should be avoided where their use is detrimental to the installation (see BS 5385-3).
5.4 Moisture movement (long-term expansion)
In common with most porous ceramic materials, tiles with water absorptions greater than 3% could expand slightly as a result of the gradual uptake of moisture irrespective of the level of dampness in the installation. Where water absorption is below 3%, tiles have negligible expansion. The fixing methods and the provision of expansion joints recommended in this standard should be followed in order to accommodate long-term expansion.