Alright guys. This strategy is super simple, and will work forever. You won't really have to repair anything, or do all that much after the initial work is done. The strategy that I have found that works the best is.... a hole. No, really. All you have to do is dig a hole through the floor of your base. If you don't want to bother with walls and the like, and have a secure upstairs, this is the way to go. Once you dig the hole, sit above where it is during the horde. The zombies will hit the ground underneath you in the whole, and dig it deeper until they can't get out. This makes it easy to go down in the morning and pick them off at your leisure. This only works perfectly for the beginning hordes though, so be careful during the later ones, as the cops can still shoot you with the goo.