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Whatever method of waterproofing is employed, whether it be a surface
applied coating or a pre-fabricated sheet membrane, the tiler should
be aware of the need to follow basic good practice to avoid damage
from cracking due to structural movement. ... All structures are subject to varying degrees of movement and the trouble to which the tradesman goes to accomodate that movement will determine the outcome of the job. ... Some principles to keep in mind are as follows:-- |
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The degree of damage due to cracking usually varies directly with
the size of the tile. It is usual to expect large tiles to show cracking
more so than mosaics. ... Structural movement mostly occurs along predictable lines and within certain areas of high stress in structures. Joints that have been designed into concrete slabs should have a corresponding movement joint included in the paving. Where large areas join smaller areas there should be provision made for differential movement. |
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Large expanses of tiling should be broken up into sections with movement
joints allowed so that sections of tiling do not exceed about 3 metres
in either direction. ... Waterproofing should form a barrier against the bonding of the tile bed to the structure. This is to be expected as the waterproofing is intended to contain moisture and to prevent moisture transmission into the structure. ... Therefore tiling on top of |
waterproofing
treatments has the advantage of separating the tiling from direct
movement stresses of the structure. Sheet membrane waterproofing,
being separate from the structure creates a much better structural
separation. ... It should always be remembered that natural stone and ceramic tiles have different rates of expansion from the structure to which they are being applied and therefore the separation is an advantage and helps in overcoming the tendency to crack. |
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Always remember that the tiling bed must :- (1) Provide adequate falls. (2) Be properly bonded to the tiles. (3) Be uniformly mixed and of sufficient strength (min 4:1) to support tiles. (4) Perform as a matrix with the tiles and if necessary contain mesh reinforcing in areas where movement is unavoidable or highly likely. ... The adjacent photograph shows you a typical disaster that was caused by bad waterproofing techniques. |
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