Before you even consider acquiring a few chickens, it is worth checking your property title deeds and maybe consult the local council in order to ascertain whether there are any laws that forbid their keeping. A small garden will likely have neighbours, some of whom may be in favour of your venture and others who may not - just have a word with them in order to gauge their opinions. Check for any holes or gaps in the boundary fences: you might enjoy the sight of free-ranging chickens, but your neighbours might think differently. Perhaps more important than the fact that your birds could escape through gaps is the very real danger of neighbouring dogs and predators gaining access. Unless your garden is well and truly fenced, it is probably wise only to let your birds have free range when you are around to keep an eye on them.
Even the smallest of back gardens is probably large enough to house a trio of birds; generally, though, the smaller the garden, the more imaginative you will need to be for space and accommodation. An area sufficient for an average-sized dog kennel and run will provide a home for three to six large chickens and a redundant aviary could house a few bantams. A garden shed can be put to good use if an outside run is attached or the interior is sectioned off to provide several smaller units. Do not use a disused greenhouse - it gets too hot and too cold for your birds.
An average-sized back garden is more than suitable for a pen of large fowl. With a large secluded garden at your disposal, there is, within reason, no limit to the breed or types of chicken you can keep; your only restriction may be how much space you wish to use and how much time you have.
For practical as well as security reasons, you might like to consider confining your chickens to a large run during the times you are not around to supervise. Generally, a run should be as big as possible and two runs can be advantageous - one in use and the other 'resting' - although this does, of course, double the area needed. Finally, no matter what the size of your garden, never forget that, as the chicken-keeping bug takes hold, you will undoubtedly need extra space for broody coops, runs, and maybe even separate penning areas for breeding stock and show birds!
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