James Hailstones, ARDEX Group training and technical support manager, discusses key considerations for uncoupling membranes
With today’s requirements for large tiles, faster installation and the use of more demanding substrates, uncoupling membranes for floor tiling are becoming a necessity.
Uncoupling provides a buffer layer between tiles and substrates to absorb lateral stress movement due to the different rates of expansion and contraction of the tile and subfloor.
In particular, newly-laid sand:cement screeds or concrete may contain large amount of moisture, which as it evaporates, causes the screed to shrink.
However, all substrates will expand and contract naturally due to humidity and/or temperature fluctuation and this is especially true where underfloor or under-tile heating has been installed.
Any movement, whether shrinkage or expansion, can cause stress cracks that can transfer through to the tiled surface, causing the tile to either fracture, or de-bond from the background. In this instance, lateral stress must be stopped before reaching the tile covering.
This can be achieved in 3-ways: separation, movement and absorption.
Separation can be achieved by using a decoupling layer – a de-bonded layer that separates the substrate and adhesive to isolate the stress from the substrate. BAL has a fully decoupling solution in BAL Flexbone 2Easy.
Movement can be achieved by installing a bonded layer (such as BAL Rapid-Mat or BAL Flexbone Varied) which moves with the lateral stress from the substrates to diffuse the movement.
Absorption can be achieved using an anti-fracture system such as BAL AF Max elastomeric tile adhesive – a material that absorbs the lateral stress from the substrate.
These systems are particularly necessary when tiling to heated screeds and are required when fixing natural stone tiles by the Stone Federation.
It is important to note that BAL AF Max isn’t like any other S2 adhesive – and using any S2 adhesive alone should not be used instead of an uncoupling or anti-fracture system.
BAL AF Max with its rubber crumb formulation is tested and guaranteed by BAL for a minimum of 25-years for its use as an anti-fracture system to replace traditional uncoupling/decoupling systems when applied in accordance with the Technical Data Sheet.
