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5 February, 2016 (10:05)

No More Cracked Tiles – Uncoupling Theory Explained

Bonding the tiles directly to the building structure creates what is known as a “force- transfer assembly” because the physical dynamics of each layer in a tile assembly are vastly different from each other. The substrate, whether it be timber, concrete, or gypsum, etc. expands and contracts due to changes in temperature and moisture levels; the tiled surface also expands and contracts, but at a different rate.

As the surface is directly — and firmly — bonded to the substrate, naturally-occurring stress cracks, and movement in the substrate, both manifest themselves in the tiles as cracks, splits, tenting, or debonding. An installed tile surface can be compared to a large sheet of glass. In addition to being a hard, brittle material, the tile also expands and contracts in reaction to environmental changes, but at a different rate from the substrate.

The solution is to install an uncoupling system – modern technology which neutralises stresses by uncoupling the building structure from the tile. This is particularly important with the use of today’s thinner, larger-format tiles and lightweight building materials.

The up-to-date method of uncoupling uses the Schlüter®-DITRA 25 polyethylene membrane, which safeguards installations over any even and load-bearing substrate.

Tiles will move independently from the screed because of different thermal expansion and contraction. Schlüter®-DITRA 25 neutralises this differential movement, preventing stresses being transferred to the tile covering. The system supports applied loads by transferring them directly to the load bearing substrate.