Poultry need space and shelter, allowing them room to roam during the day, while allowing protection for the wind and rain, including somewhere secure and warm to roost at night. A hen house should be secure, dry and well-ventilated with enough nest boxes for the number of birds (approximately one for every three or four birds). Each nest box should be large enough for birds to move around in, but not so large that more than one bird at a time can use them.
Thought should be given to security – while poultry are generally poor fliers, some chickens can clear fences that are 2 metres high, and a few specialist breeds may require netted roofs.
There should be at least one perch inside the house, preferable more to allow choice. This should be at least 5cm wide for large fowl, slightly narrower for smaller breeds. The top corners of the perch should have rounded edges. Perches should all be offered at the same height to prevent squabbling between birds. Perches should be above nest box level, so that birds are not encouraged to sleep in the nest boxes (they will automatically choose to roost in the highest possible place). A removable droppings tray placed under the perches will make cleaning the house easier. Large breeds may require a ramp or ladder to enable them to reach the perches easily.
Access to nest boxes from outside the house will make life easier, as will a small pop hole, to allow birds to move into the house during the day if they wish, but which can be shut at night for security.
Ventilation is particularly important, with air holes or shuttered windows near the roof line allowing hot air to escape.
Ideally a hen house should be 1 x 1 metre per three or four birds, many prefabricated houses will be marketed as being able to house more birds than this, but this will be an absolute maximum, and poultry will be far happier if given more space.