Sealing on Styrodur insulation?

: 1.) In the area of ceilings, the use of Styrodur strips often poses no problem at all. As a rule, the compressive stress limits of the masonry are not reached in the upper floors. However, it can be quite different in the lower floor. Especially in areas such as masonry pillars (between two large windows to the terrace), the limit compressive stresses of the masonry are often reached. If a part of the bearing surface of the stone is missing, failure can occur.

2.) Just because Styrodur is increasingly used for decoupling the floor slab in new buildings does not make this mistake any more correct. In case of damage, this issue will come back to haunt the planner and/or the executor. Aside from the fact that this execution is not DIN-compliant, the manufacturers of the sealing materials specify mineral substrates as the basis. Styrodur is not mineral and therefore does not meet the requirements of the manufacturers or the building supervision approval of the material. If it is still executed this way and damage occurs, the expert will classify the execution as non-compliant or defective.

I would like to activate this thread because I have a similar question regarding a position in my rough construction offer. We are building with a basement and the offer states...

Position 5.14: Insulation of the basement exterior walls made of Styrodur 120mm up to the upper edge of the basement ceiling.

Optional position:
Surcharge to Pos. 5.14 full-surface bonding of the Styrodur boards on the basement exterior walls with bitumen thick coating.

The optional position would cost me 2800€ net.
Here the rough builder and the architect mean that the position is only indicated based on manufacturer recommendations and they want to cover themselves with the recommendation.

A sealing with thick slurry would be sufficient here based on experience. But the decision is up to me.

Since I have no idea, I wanted to ask here how it was done with you?

I would skip WU-Keller. The part is already sealed. Why smear "black" over "white" again?