- availability of food, clothes, fuel and other useful items;
- availability of fresh water;
- possibilities of fortification;
- number of escape routes;
- concentration of zombies.
Exit/entry options
You know those superspy films when the agent takes mental note of all possible exits in any building he enters? You'll have to adopt the same kind of attitude whenever you select a building to fortify. If you find a building which can be easily converted into a fortification you should take into consideration that the best fortification in the world can easily be converted into the safest trap in the world if you find yourself under siege without the possibility to leave to find food and other supplies. So any fortification should have several exits. You should also consider making several options for entry available. Don't forget that zombies have very limited capabilities, so a simple ladder should be too much of a challenge for a zombie, leaving you with a simple solution to enter your base in a hurry.Dangerous areas
Ground level building areas are hard to fortify, especially in recent buildings where there are often big glass surfaces. Another problem is that if you use ground level areas, to best fortify them you will probably have to cover windows and block doors which will result in very dark rooms. This will be both depressing and a security risk because if a zombie manages to walk in it is more likely to surprise you in the dark. The ideal solution would be to block any doors and windows with bricks, vehicles or whatever you have at hand that will stop zombies from occupying the lower levels and making that area an hazard zone. You should also lock down any access from the ground level to the higher levels of the building.Locking down building areas
Modern apartment buildings are fairly easy to contain internally. Fire regulations mandate that accesses to internal stairwells should all have fire doors. These are usually metal doors which expand when exposed to high temperatures. Although having a big area available may seem interesting, the bigger the area, the harder the maintenance of the security measures and the higher the risks. Therefore you should limit the area of a building you are using to a manageable dimension. All other areas should be locked down to prevent access to the area in use. An easy way to do this would be to weld the fire doors. After welding you can sleep safely because those doors will easily hold a horde of zombies. Another advantage is that if in the future you decide you want to expand your living area, it is still possible to remove the welding spots. For the intended purpose, you won't need to be a master welder. A few well place welds will makecave dry batteries to which you just have to add destilled water to produce electricity. The good thing about these batteries is that as long as they are kept dry, they don't have an expiration date. The gas for option has a number of issues, namely the difficulty opinion obtaining gas canisters, for instance oxygen and acetylene, and there also risks of explosion if you don't know what you're doing.To know your options take a look at this Wikipedia entry.
A roof and walls and be happy about it
Securing an apartment or a set of apartments is not going to give you much more than a dry and safe place. As you might expect, all the perks of modern society will have been stripped out of existence by a zombiepocalipse. There will not be running water, cooking gas or electricity. The good news is that two out of three have solutions. Cooking will depend on burning fuels like coal and wood, being that for coal you will only be able to count on with whatever is left in the local supermarkets and such stores. You may also be able to find camping gas canisters, which will bring your cooking experience to the pre-apocalypse era. For electricity you may be able to set up some solar panels but there is more to it than just dumping some panels on the ceiling. You'll need an inverter and batteries, which may not be that easy to find and set up. If you really want performance you could even assemble a solar tracker, but that's probably not a priority. Now, that is all very pretty, but in all honesty, cooking gas and electricity are a rich man's luxury. Without water everything else is superfluous. Without water you will not last long enough to care about the lack of electricity. So, running water may be too much to wish for in the midst of the zombiepocalypse, but you'll definitely need a minimal amount of drinking water, so that should be one of your top priorities. Bottled water is an obvious solution, but even if the area supermarkets haven't all been ransacked, you'll eventually have to find a way to collect water and purify it. It turns out that exposing closed bottles of water to sunlight can eliminate bacteria and microbes and render the water safe for consumption. This process works only if the water is clear enough to allow reading a newspaper placed under the vertically placed water filled bottle. The purification can take up to several days depending on the amount of sunlight available. There are other options like collecting rainwater. Drinking untreated water is usually a very good way to die slowly and painfully from intestinal parasites, so do invest some time in understanding how to purify water. It always pays.
Solving the drinking water issue is a big step towards long term survival, but there are other water related topics to take care of that you used to take for granted in a working city. The lack of running water, together with the absence of maintenance to the city sewers means that you will not be able to use a bathroom inside an apartment. Options will have to be considered, like the use of plastic bags and posterior treatment of the waste materials.You always have the option to throw human waste out the window like they used to do in the dark ages, but we all know that's not such a good solution. It will attract insects like flies which will eventually land on your food and cause dysentery. Not to mention the smell, the tell-tale that someone lives in the area and there's always the possibility that the smell will attract zombies. Who knows what teases a zombie's appetite?
This topic would require a blog by itself, but I think it is a good start for a series on urban survival on a zombiepocalypse.
