I pride myself on not being an early adopter but in this case all I can say is 😳

Yep, Dylan and Martha are right. Roofmaterial is part of the underlying original picture, no modelling done on that. Thanks again for comments 😄

Thank you. That was it.

Thanks Rich, that's a good idea! I'm gonna give it a go.

If anyone else has good suggetions, please let me know 😄

Thanks Cyberdactil, I guess in that case it is indeed a ballasted membrane.

Gonna study this info from you, as my clientbase is expanding to include more international clients it's a good thing to know the english words 😄