ᐅ Adhesive for Styrofoam insulation on WeberSuperflex D2

Hello everyone,

Although I am not currently building, renovating, or restoring a house, I am installing a pool (like probably half of Germany). I have treated and prepared the exterior walls according to the manufacturer’s instructions and then applied a waterproof slurry, WeberSuperflex D2, completely over them. Now I would like to glue Styrodur insulation boards onto the waterproof slurry.

So here is my question:
Which adhesive am I allowed to use? I haven't been able to find any information about this online.

Can anyone help me?

Thank you in advance.

Best regards,
Navegante