AS you dont seem to be able to modify building how do you manage to build on them as z'd just run up stairs even inside buildings and you cant build on most of them
Buildings in the game may have added crafted items like walls, floors, poles, etc... There is one item that will also allow you to control a great deal of the direction a zombie will take...use a Fence.
The Fence is a very powerful crafted item. Do not forget that you can stack them very high! Most crafted items will eventually break due to zombies beating on them. Uses Fences to direct zombies into your traps or away from your buildings.