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Well there are some things that would be a bit strange after zombies. First living would/should be communal, because though that causes faster spread of disease, it is far more defensible. Which is more important when a singe zombie can fuck you all over by sneaking into someone's room at night. Fear tends to drive people together, or apart, people driven away from others will not likely even try to live in towns having no real effect on their layouts. Also if your daytime is full of zombies trying to eat you, your dreams will likely be similar. Sleeping in a group, or at least near other people would help with nightmares and make it easier to calm down after one.
For that reason also people should tend to pick a single building and level everything near it, living together in a single structure that people/zombies can't sneak up to. Now while that might make the location rather conspicuous to people, if you have enough people, not being conspicuous would be nearly impossible, particularly if you are farming. However if there are no individual buildings that can hold all of your people a group of connected/nearby buildings may work well, such as a school campus, though individual apartment buildings may be better they might not hold the required functionality. Another option would be to build up around the base of the main building, or connect it to another building through new construction. Lastly one might split the group and take multiple buildings and pack people in them as needed. Basically though you would be seeking a very high population density, because that way the number of guards vs other workers allows greater flexibility.
As for fortifying your structures, a basic wall may be enough against zombies, even a chain-link fence could be enough if it is far enough away from the structure. Against humans you are kind of screwed when it comes to fortification, not much that you could build would be able to handle a truck that has a brick on the gas pedal sent vaguely in its direction, or any of the other fairly cheap options that would be available to attackers. So your best defense may be open space for your guards to pick off attackers before they get close, possibly with a very rough rubble field past that to block vehicular assaults.