The merchant's house - now known simply as the Town House - was dismantled, restored and reconstructed by Gunolt Greiner, a German-born craftsman, and his son Francis. They worked to a rule of strict honesty: where the original details were known they reproduced them; where they were unknown they used plain, unembellished oak so that no visitor would ever mistake a guess for evidence. The result is a building that wears its own scholarship lightly. The same father-and-son team went on to reassemble the windmill and the granary at Avoncroft, then moved on to other open-air museums in England, including the Bayleaf Farmhouse and Market Guildhall at the Weald and Downland near Chichester. Their habit of marking new oak with restraint became a quiet standard across the British conservation movement.

The collection at Avoncroft now runs to more than thirty structures spanning over 700 years. There is a chain-makers' workshop and a cell block, a counting house and an earth closet, an ice house and a 16th-century threshing barn. The granary stands on staddle stones to keep the rats out. The windmill turns - actually turns, in a stiff westerly - and grinds flour by appointment. A perry mill from Redditch presses pears. A tollhouse from Little Malvern still has the painted board listing the prices for cattle, sheep and laden carts. A fibreglass church spire from Smethwick, rescued because no other museum would touch it, leans peculiarly in a corner of the field. A cockpit for cockfighting, illegal since 1835, sits on the grass as a small, dark reminder of what country sport once was.

Two buildings on the site are easy to overlook and hold the most surprising stories. The first is a prefab - an Arcon V, one of the emergency post-war houses that were thrown up in their thousands after the Second World War to replace bombed-out homes. This particular one came from Moat Lane in Yardley, Birmingham, and was moved to Avoncroft in 1981. It still has its little bathroom built around a galvanised-steel cabinet, its compact kitchen, its window onto a notional 1947 garden. The second is the New Guesten Hall, built specifically to house an extraordinary thing: the original timber roof of the Guesten Hall that once stood beside Worcester Cathedral, the chamber where the Prior received his important guests. The roof is medieval; the walls around it are modern; the licence covers wedding receptions and conferences. The medieval craftsmen who shaped those oak trusses would not have predicted that ending.

Avoncroft also holds the UK's National Telephone Kiosk Collection - the largest single gathering of British phone boxes in the country. The familiar red K2 from 1924, designed by Giles Gilbert Scott. The K6, the smaller red box that proliferated in 1936. The K8, the K3 in concrete, the experimental designs that never quite caught on. A Glasgow Police Box stands among them, a tall blue rectangle that looks unmistakably like the TARDIS from Doctor Who - because of course the TARDIS was modelled on exactly this object. Behind the kiosks sit three working manual telephone exchanges, including BT's last Strowger electromechanical exchange, all wired up and demonstrable. A guided tour will route a call through them by hand, as it would have been routed in 1950.

Every building at Avoncroft was moved to save it. Some had been threatened by road schemes. Some had been condemned as unfit. Some had simply fallen so far out of use that demolition was cheaper than repair. Taken individually each rescue is a small story; taken together they make a different point. The architecture of ordinary life - barns, prefabs, toll houses, chain shops - is exactly the architecture that gets thrown away first when no one is paying attention. Avoncroft pays attention. The events programme keeps the place lively with Wars of the Roses re-enactors and 1940s weekends. The buildings, meanwhile, stand patient on their new ground, waiting to be walked through by the next school party that has never seen an outside toilet or a working windmill.