Decoupling Membrane
There are loads of instances where a
decoupling membrane is essential.
The primary purpose of a decoupler
is to separate your tiled area from the sub-base which may be subject to tension across the surface. Screeds with underfloor heating in will expand and contract during the heating up and cooling down process,this can cause cracks in the screed that will transfer to the surface.
Floors over boarded with plywood are also vulnerable .Plywood will expend and contact as it warm and cools separating the joints.
Newly installed screeds as they dry out
will shrink,expand or even crack,that is why it so important to commision underfloor heating systems correctly.
All the above are instances where you
might want to use membrane.and they are all examples of where the movement in the substrate can crack your finished tile surface