James Hailstones, ARDEX Group training and technical support manager, examines the myths that surround uncoupling systems and outlines why the right approach to movement management can make all the difference to a tiled floor’s durability.
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 owing to the different rates of expansion and contraction of the tile and subfloor.
In particular, newly-laid sand:cement screeds or concrete may contain a large amount of moisture, which as it evaporates, causes the screed to shrink.
However, all substrates will expand and contract naturally owing to humidity and/or temperature fluctuation, and this is especially true where under floor or under-tile heating has been installed.
What’s more, certain water-sensitive substrates, such as anhydrite screeds (or calcium sulfate) will lose their cohesive strength if they get wet. Wood is a hygroscopic material, and this, therefore, increases the potential risk of dimensional changes occurring within boards owing to moisture expansion and drying shrinkage movement resulting in lateral movement stress being generated between the board background and the rigid ceramic tile finish.
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 debond 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 debonded 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 which moves with the lateral stress from the substrates to diffuse the movement.
Absorption can be achieved using an anti-fracture system – 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.
James Hailstones
ARDEX Group training and technical support manager
www.ardex.com
