And yes...for those who've asked, if you build more than one and don't use the helipad/runway, they are indeed modular. ( I only took this pic to show it can be done, but you would have to modify a few things, but it does work) If I left it like this I'd brace the walls a little more though. Personally I like building them out beside one another, but if you want to build upwards this shows you can.