There is something quietly satisfying about turning a stack of weathered boards into a home for your hens. Reclaimed timber is cheap, often free, and it has already proved it can stand up to British weather. But a chicken coop is not just a box with a door. Get the dimensions, ventilation and height off the ground right and you will have healthy birds and far less cleaning. Get them wrong and you will be treating respiratory problems and red mite for years.

Choosing and Preparing Reclaimed Timber

Start by sorting your pile honestly. Anything soft, crumbly or riddled with woodworm goes on the fire. What you want is sound timber that rings when you tap it.

• Frame: 50mm x 100mm (4x2) or 50mm x 75mm (3x2) for legs, base rails and roof rafters.
• Cladding: feather edge boards, tongue-and-groove, or old scaffold boards ripped down. Feather edge is ideal because the overlaps shed water.
• Floor: 18mm ply or exterior-grade board. Avoid chipboard and MDF entirely — one damp winter and they turn to mush.
• Avoid: any timber that has been soaked in old-style creosote, and anything carrying flaking lead-based paint. Both are a risk to birds that peck at everything.

Scrub boards down with a stiff brush, let them dry thoroughly, and stack them with spacers between the layers while you plan. Pull every old nail — a magnet on a stick saves a lot of swearing.

Size the Coop to Your Flock

Measure your birds before you cut a single board. Under-sized housing is the most common mistake, and it leads to bullying, feather pecking and dirty eggs.

• Floor space: roughly 0.1 to 0.15 square metres per bird inside the house, with more for large breeds such as Orpingtons.
• Perch: 25 to 30 centimetres of perch length per bird. A 40mm to 50mm wide timber with the top corners rounded off suits their feet well.
• Nest boxes: one 30cm x 30cm box for every four to five hens, sited in the darkest corner.
• Pop hole: 30cm wide and 35cm to 40cm high clears most heavy breeds comfortably.

Allow 60cm of headroom at the back of the coop and 90cm at the front if you are building a sloping roof. You will thank yourself every time you reach inside with a bucket and scraper.

Siting, Ventilation and Raising It Off the Ground

Damp is the enemy. Stand the coop on legs, concrete blocks or a paved base so the floor sits at least 30cm to 45cm above soil level. Air then moves underneath, the timber stays dry, and rats and mice have far less cover.

Ventilation matters more than warmth. Hens cope with cold well but tolerate stale, ammonia-heavy air badly. Aim for roughly one-tenth of the floor area given over to ventilation, positioned high up near the eaves, above the birds' heads when they perch. A gap of 25mm under a generous roof overhang, backed with 6mm weldmesh, works beautifully. What you must avoid is a draught at perch height — that is what causes chilled, sickly birds.

Face the pop hole away from the prevailing wind, and if you can, site the coop so the entrance catches morning sun. Dry out the ground around the run with a layer of woodchip or gravel.

Frame, Roof and Cladding

Build the base frame first and check it for square by measuring the diagonals. Set your uprights at no more than 600mm centres so the cladding has proper support and the whole structure stays rigid.

Give the roof a fall of at least 15 degrees and let it overhang the walls by 50mm to 75mm on every side. That overhang is what keeps driving rain off the cladding and away from the ventilation gap. Onduline sheets or mineral felt over exterior ply both do the job, and both are easy to replace later.

Fix feather edge boards with a 25mm to 30mm overlap, working from the bottom up so water runs off rather than into the joints. Leave a small gap behind the boards at the top to feed the eaves ventilation.

Perches, Nest Boxes and the Interior Fit-Out

Keep the inside simple and easy to clean. Line the floor with vinyl or a removable ply tray, and fit a droppings board beneath the perch that slides out for scraping.

• Make perches removable so you can scrub them and inspect the ends for red mite.
• Fit nest boxes with a lip at the front to stop eggs rolling out, and a lift-off lid for collecting.
• Dust cracks and joints with diatomaceous earth when you build, and check monthly through the warmer months.

Use galvanised screws throughout rather than nails. Reclaimed timber is often hard and slightly twisted, and screws hold it far better — plus you can take the coop apart for repairs.

Fixings, Predators and a Maintenance Rhythm

A fox will test every weakness in the first week or two, usually around dusk. Line the run with 25mm weldmesh rather than chicken wire, which a determined fox will tear straight through. Bury the mesh 30cm into the ground, or turn it outwards as an apron and peg it down.

Secure the pop hole with two bolts — one at the top, one at the bottom — and check the hinges are screwed into solid timber, not just cladding. Latches that a badger or a clever hen can nudge open are worth replacing.

Once a year, walk round with a screwdriver and probe the base rails and the bottom 100mm of cladding. That is where rot begins. Replace a board early and the coop will give you a decade or more of service. Built well from salvaged timber, it costs very little, looks right in a farmyard, and keeps your flock dry, safe and laying.