One of the most crucial aspects in surviving a Zombie infestation is setting up a well designed network of hideouts centered around a well fortified home base. A home base should be located at a familiar place, and one of the highest points available to you. your view of the surrounding area is key, and will give you a much needed edge against the living dead. As far as construction goes it will need to have multiple entrances, and tunnels if you can accomplish that, all of which can be secured or blocked off if needed. reinforced concrete is your ideal material, and if windows are to your liking bulletproof plexiglass will do nicely. Unfortunately, since most people do not have the luxury of creating the perfect stronghold before the infestation hits they are forced to make due with what they have around them. If this is your case, then you will need to make due. It's a common mistake to use higher floors for protection, while this will get you elevated, it limits your access and often proves fatal. The best readily available structure is a two story shopping mall of the "+" shaped variety. It is large enough to give you room to move about, and has enough entrances that you will always be able to find a clear way in or out. Most of these shopping malls are very secure to begin with, but just to be cautious a second runthrough is always recommended.