So I am currently building a museum for a school project. So the problem I have is when I have the interior walls touching the roof, from outside you can see the lines of the walls. I want to not be able to see these lines, however upon deleting them the walls disappear. Thanks
Why not model your project just as it would be constructed? Your roof slab is going to have a specific thickness and there may even be an interstitial layer below it to conceal mechanical, electrical and communication lines with a ceiling below that. If you model the roof slab and the ceiling, your walls would normally terminate at the ceiling line (unless they were intended to function as fire barriers, in which case they will terminate at the underside of the roof). In either case the top of your walls would not be visible when viewed from above.