Well I was curious as to where people plan to make their stongholds. A two-story house, a store, etc.
Personally I have an interesting new one that I have never heard of before in mind. One that I just recently thought of while just driving in town was a parking garage. It is made of some solid reinforced concrete. The top floor could be modified to be made into a farm for your crops, contain a greenhouse, and a place for solar panels, as well as a few lookout posts. The other floors could be the barracks, supplies, etc. The ramp leading into the garage could be blockaded with vehicles, or just destroyed, although it is the harder of the two but safer. You could also enclose exposed floors from the weather with wood and other construction materials.
All in all it wouldn't be too hard to fortify one of these badboys into a zombie proof fortress in my mind. I'm interested in hearing your comments, and also your other ideas for a stronghold.