Greenhouse roofs.

I'm curious to see how they dealt with the side that fits against the regular wall like with a pentroof. I hope I'm describing it the right way. Currently it automatically appears like a dry wall and can be colored but not deleted which would make complex roof structures look very strange and defeat the purpose. I am trying to rebuild the Vienna Palmhouse and if the undeletable drywall stays... I will have to scrap that ptoject because that structure is constructed with hardly any regular walls at all.

https://www.viennainside.at/wien/freizeit/urban-exploring/palmenhaus-schoenbrunn-bei-nacht/