Not Quite Architecture: Happiness is a corrugated roof and a scratching post

ARK ESTATES are a new form of mass-produced housing spreading across the English countryside. These are not designed for executives in shiny suits yearning for a Joke Oak house with double garage in a green-belt cul-de-sac. They are being built for the nation's pigs.

After years of being hidden away in cramped farm buildings and redundant goods wagons, pigs are being offered detached homes of their own in agreeable rural settings. For less than pounds 200, a snout of six or eight sows, or a grunt of four boars, can snuggle together in their own sty, sweet sty. These corrugated metal or hardboard ply homes, known as 'arks' or 'arcs', are popping up almost as fast as neo-Georgian estates. They are becoming a regular feature of the English farmscape and are expected to spread further as more and more pigs are rehoused in fields.

To date, only 18 per cent of England's pig population lives in arks. Over the past 30 years, farmers have found that pigs are happier, healthier and fetch higher prices when they live a life of rural bliss. A happy pig likes a well insulated and ventilated ark to sleep in, a field to roam, a post to rub against and a muddy stream to wallow in on hot days. A perfectly happy pig dreams of a home with a veranda. On mild days, pigs like to watch the world from the comfort of their verandas, offering no more than a twitching snout to the world beyond.

A contented sow will grow to be big - she needs at least 6ft to turn around in and a door to her ark no less than 3ft 6in high - and give birth to three litters of eight piglets each year. No wonder farmers are investing in this latest form of housing rather than selling off every inch of land they can for holiday homes for two-legged swine.

Before the success of the ark, pigs had become more or less invisible. Where once they had roamed in herds through woods and coppices rooting for acorns under the watch of a swineherd, the enclosure of common land in the 18th century forced them into the confines of farmyard sties. Many lived in houses, fed on waste from dairy products, and produced - along with pungent smells - a form of primitive or porcine central heating. The ideal sty was topped by a poultry loft: the pigs kept the hens warm, while the hens' droppings insulated the pigs' ceiling. The whole caboodle warmed the farmhouse.

Without proper exercise, and fed on rich swill, England's pigs waxed fat and lost their hair. Doting farmers had ideal sties built for their prize specimens. The 'most nearly perfect pigsty in England' was built at Petworth, the great Sussex estate, in the 1790s. Each pig enjoyed its own daytime exercise yard and night-time shelter. These radiated out in a fan-shaped pattern from a central boiler, granary and feeding point. Two small versions of the Petworth Hoggery can be seen at Blists Hill Open Air Museum at Telford in Shropshire.

At Fyling Hall, North Yorkshire, Squire Barry went a step further and, 100 years ago, built his pigs a colourful classical temple overlooking Robin Hood's Bay. Today, you can make a pig of yourself here courtesy of the Landmark Trust, which has converted this most handsome of all sties into a memorable holiday cottage.

Pigs began to emerge from sties, converted railway carriages and dog-kennels in the Sixties. At the same time as local authority architects designed massive estates for their two-legged cousins, pigs were introduced to the joys of mass-produced homes.

Ark estates are best built on sandy, chalky or gravelly soil. Ideally, arks are sited on arable land farmed on a rotational basis. The pigs move with the cycle of crop growing, their waste feeding the soil. Individual arks are moved from time to time, the straw the pigs lie on burnt and so disease kept at bay.

To date, the design of arks owes about as much to the imagination as a typical developer's mock Tudor or neo-Georgian house. Two styles dominate the pig housing market. The first is a semi-circular hut, rather like a Nissen hut, made from five corrugated iron sheets wrapped over a wooden frame. The second - a superior design in terms of insulation - is made of hardboard ply over a steel frame. These can be erected in 15 minutes. A window at the back enables farmhands to check if sows are lying on their new- born piglets, something they are prone to do.

It is unlikely that farmers will commission architects to improve these designs, although as ark estates continue to spread across the country there are bound to be pleas for better-looking versions. However, as farmers are still largely free from the strictures of planners, pigs might fly.

(Photographs omitted)