The Darkroom
To create a darkroom, you really only need a (pardon the mauling of the quote) ‘a clean, well-ventilated space’. That you can get dark.
At least that’s a start. The usual problem exists in this discussion: there’s not time to go into every detail. I’ll probably get sidetracked as I go along anyway. There are also references (books, magazine articles, and sites) that do go into detail. So, on with the big picture.
The Space
It’s actually pretty surprising what you can get away with, and without, in terms of space. If you are thinking in terms of a permanent darkroom, then opting for more rather than less square footage is probably wise. Even with a permanent set-up, you can get by with as little as 15 to 20 sqare feet. That’s going to be really tight, and probably without running water, but it can be done.
In terms of space, work with what you have. That sounds pretty obvious, but planning will really help make the best use of space, and make working in that space more efficient. At minimum you will need a solid, stable surface for your enlarger, with some kind of storage, and the same for processing chemistry.
If you have running water in the space, keep the enlarger on the other side of the space, creating a dry side and a wet side. If you don’t have water, you’ll still need room for your processing trays. I’ve seen designs where these are sort of stacked in a rack, but I don’t think that would be too fun to work with. So figure on two counters, or a counter and a sink, on opposite walls.
With this initial design, think about the door. In the illustration, it opens into the room, with the hinge on the dry side. This will not prevent accidental exposure, but you have a better shot at losing less if the light coming in hits the wet side—you would be less likely to have an open box of paper sitting in the sink, right?
See? I’m wandering off on tangents already. The important thing about the space is to see what you have, and then plan accordingly.
Juice
For most of us, the electrical requirements are fairly standard. What I mean is that you will most likely be able to use what you’ve got, typically a 15 amp grounded circuit. Just plug it in.
To get more precise, and to get closer to code, we can talk about ideal. On the dry side, a dedicated 20 amp circuit to run the timer, a safelight, and the enlarger. This will be enough juice for all of the above. The dedicated circuit will help (but won’t prevent) voltage drops. This typically will happen when, say, your central air conditioning kicks on. Ever notice your lights dim for a second? That’s from a jump on the load. This will happen to your enlarger as well. Short of putting in voltage stabilization, there isn’t much to be done. Unless your timimg is really awful, it will be pretty rare that you pop your timer the same time the A/C kicks on. If this is really a concern, look at UPS devices (for computers), which as well as the power back-up, provide ‘cleaner’, stable current.
On the wet side, and this is a code and safety issue, any outlet within 12 inches of water should be protected by a GFCI outlet. GFCI stands for ‘ground fault circuit interrupter’, and will keep you from being electrocuted. That’s why they are in bathrooms. Just do it, or have it done. As well, use the units installed at the outlet, not in the breaker box. They are faster, and less susceptable to popping with normal fluctuations. Talk to your electrician. A single dual-outlet receptacle should be enough over here, to run a safelight and a processing timer. You may not need any at all, depending on how things are set up and what equipment you are using.
Sealant
Your darkroom does not need to be hermetically sealed. In fact, that is a bad idea. You need some ventilation. Light-tight does not need to be air tight.
As for light-tight, do as good as you can, depending on what you have to work with, then test the room. Leave a piece of paper sitting out for a few times the normal exposure-to-fixing time, with your safelights on, then process it. If it’s still white, you’re good to go. Not exactly the most scientific method, but it’s a pretty good indicator.
Some circumstances may require that you only work at night, or not during certain pparts of the day. I’ve had that situation in an aprtment, and it was fine for occasional printing.
Surfaces
Ideally, all surfaces should be both no-reflective and non-porous, especially the floor. Carpet is pretty much out, or will be if you have it on the floor and do much printing.
Water
You will need quantities of reasonably temperature controlled water. Not a huge amount, and not continuous, but a fair amount. The source, as mentioned above, doesn’t need to be in the darkroom. You also need disposal. This is black and white, not color, so with dilution it can go through, um, normal channels. Except if you are on a septic tank system. I don’t know if there is chemistry available that doesn’t kill that which makes septic tanks work, so do some research. I did know a photographer who couldn’t work at home because they used a septic system, and she had to rent a studio/darkroom in town.
