Ok, here are some very prelimary plans. We should think about starting constructing quickly as a zombie apocalypse could happen at any moment. The plans are intentially small-scale to help building quickly.
Blue- That is the moat we have all been talking about. I've added some spears all around, although I'm sure a better idea is out there.
Red- Very heavy steel drawbridge. We need an engineer to help as this will have to be able to also operated manually if generator runs out of fuel (more on this later)
Green- Steel shutters. I'm thinking plantation style, although this is still open to discussion.
"T" Circles- Turrets, of course. Something along these lines.
Pink- Staircase. Stairs to the basement are equiped with a large steel cover. The basement will be the last line of defence and must be protected the most.
AC- Armored car. We may need to be able to access the outside world. I'm thinking an armorer Hummer with a zombie cowcatcher. Maybe a smaller turret on top, Halo style warthog?
Walls- Need to be concrete walls. I'm not too sure about the 45 degree walls, we would have to do some testing before we know they are safe. What if the piles of dead zombies allow enough traction for others to get onto the roof?
Ok, The roof.
WT- Watchtower. dsetterl suggested a good one, I believe.
T- Another turret
H- Helipad! We may need rescue. I don't think we can afford a helicopter to have stashed there at first, but if it's in the budget than we should buy it.
Basement, last line of defence. Like I said, the pink needs to be a large, heavy steel hatch. We have two bedrooms, designed to support about 4-6 people. Bathroom, but we may have to accept this will be sans plumbing.
Blue Circles- Water tanks. I'm thinking we can squeeze 400-500 gallons. Water is the most important aspect to zombie survival.
Brown shelves- Food storage. We can only use dry, unperishable food. Spaceman food.