Building a house for your hens must start with the birds. There is nothing like a wet hen—when they are damp they act really, really annoyed. They are also susceptible to disease, so putting a roof over their heads is critically important. Hens like safe, enclosed nesting areas so will gravitate to a dark corner if they don't have a satisfactory nest. From the roof down, everything should be dictated by the need to keep your chickens well watered and fed as well as reasonably clean.
Once you've addressed the needs of your chickens, then you can begin to add elements that make your life easier. The following are worth considering:
Your hen house and coop benefit from being tall enough for you to open a door and walk into it. Though your hens don't care—they can literally live year around in a chicken tractor—you will find that accommodating yourself makes it much easier to maintain your birds. The coop should have at least 4 square feet per bird, so if you have four birds, you'll need a coop that is at least 4'x4'. Some folks say you can get by with less space (about 3 square feet), but if you have it, flaunt it. We have a coop that is about 8' wide x 8' long and 6' high which provides very comfortable digs for six birds.
The size of the hen house, which contains the nests and roosts, needs to accommodate the number of birds you have (or aspire to) and be large enough for you to walk into and turn around. It could easily be smaller though, as long as you can get into it to clean and collect eggs. Hinging the roof so it lifts up or has exterior doors into the nests is a perfectly satisfactory approach.
Windows are good, especially if they open. They should be screened to provide ventilation. Cross ventilation is important so include vents on the wall opposite the window.
Once the minimum size has been met which works for the birds, the rest is gravy. Doors of some sort are good: some people like solid, others prefer screen doors. Your climate will determine the type. Add two at different points to make access easier, especially if your design is on the small side. Include a chicken door that opens to a ramp so the chickens can easily access the coop.
You can buy brand new materials for your hen house and coop to make it the Taj Mahal among coops or build it from scrap. The birds don't care, so suit your own aesthetic predisposition. Many great architects and builders started with chicken coops, so test your design and construction skills. A well-designed and maintained chicken coop and hen house is a credit to its owner.
Two by fours and chicken wire are the customary materials, though other wire is fine as long as your birds can't get out and other critters can't get in.
Build the house on concrete blocks and use solid wood flooring to prevent rats and snakes from getting in.
Consider ease of cleaning when you select materials, since you'll need to wash the hen house down annually (preferably during your dry season).
If your climate is very cold, insulation will make the long winter less taxing on your girls.
Coops are sold online and at feed stores. There's nothing wrong with any of them. They may seem expensive, but building materials can add up fast so plan your coop down to the nails and door hinges before building. Once you have a materials list, it will give you a better idea of the relative cost.
Small tool sheds and chain link kennels with tarp roofs at your home improvement store can work as well as repurposing a larger dog house found on craigslist.
Regardless of what you use, as long as you meet your chickens' needs, you'll have happy birds and plenty of fresh eggs.
For construction help, find an experienced carpenter at ContractorNexus .