Does a foil need to be installed with tileable insulation screed?

Tiled insulation screed is best installed without foil, so it adheres to the substrate.

You can improve the adhesion of the tileable insulation screed by moistening the concrete substrate with water the evening before.

If there is a risk of rising damp, it is best to install a foil. For extra security, you can place a screed reinforcement mesh on the foil (in combination with the Staenis grid) to prevent the insulation screed from bulging.