I think I got a decent idea for this actually.
Go into the 3D editor, open whatever map you wanna change. Put any building without loot that you wanna use as base, and just barricade with whatever you wanna barricade with. Entering and exiting might become a problem. But there are ways to lock the zombies out of your base.
Or just download a mission with basebuilding (I'd really recommend Haleks Factions release). He got an updated basebuilding system that is damn great. And build yourself a safe base. The walking dead all over again!
Happy surviving!