Ladder in Evergreen Harbour Apartments

I was building in one of the apartments in Evergreen Harbour and I kinda wanted to see if I could place a ladder to the roof and it let me place it. It didn't make a cut out of the square to climb through so I tried to get rid of it. I can't click on it or sledge hammer it and when I tried to bulldoze it, my game crashes, well it permanently loads not crashes. 

What do I do because it's so annoying?