It was a wild and windy December night when disaster struck Ben Eadar. Woken at half past five in the morning by a crackling sound above his head, John T. Davis thought at first that hailstones were sweeping in off Belfast Lough and bouncing against the roof of the house. But as the sound continued and intensified, he got up to investigate, climbing up to open a trapdoor in the attic. Thick, black smoke poured out into his face.

"That was enough for me," he recalls. "I pulled the door down quickly, with all these notions of backdraughts flowing down into the house." By the time Davis, his partner Lesley and son Caolaidhe were out the front door, they could see flames coming out of the roof.

It seemed like an age before the fire brigade arrived, and when they got there they appeared to John to have difficulty getting enough water from the hydrants. "They had to take water out of the lough," he says. "Luckily, the tide was in at the time, but of course salt water does outrageous damage."

John stood and watched as Ben Edar, the house in Holywood, Co Down he had lived in for 25 years, collapsed in on itself. "At one point the firemen turned to me and said `What do you really want to take out of this place?' ", he recalls. "You're standing there, watching your house burning, and there goes one room, then another, then you wonder is the whole thing going to go. It seems incredible at first and you can't really believe it.

It'll be an indelible image in my mind for ever. The ceilings came down, and the water damaged everything. The whole top floor and attic is completely gone."

There is nothing left in the charred debris to give a clue as to how the fire started, although an electrical fault is suspected. There had been smoke alarms all over the house, except in the attic - which John thinks other people should take note of. He knows that they were lucky to escape unharmed, but the damage is still heartbreaking.

For almost three decades, John T. Davis has been making some of the finest documentaries of his generation - Power in the Blood, Dust on the Bible and Hobo among them. Ben Eadar housed much of the record of those films: photographs, out-takes and - in the case of his earliest work - unique copies. Most of that is gone now. The fire makes Davis's 1996 documentary, The Uncle Jack, an elegy to his uncle, John ("Jack") McBride Neill, seem even more poignant.

McBride Neill, the architect of most of Northern Ireland's cinemas during the Golden Age of movies in the 1930s, bequeathed Ben Eadar to Davis, and gave him his first movie camera. Ironically it was the burning "by persons unknown" of his architectural masterpiece, the Tonic Cinema in Bangor, in 1992 which set Davis off on a journey of exploration and self-discovery that became The Uncle Jack, a gruelling four-year process of self-examination and exploration, much of it shot in the house and on the shores of Belfast Lough, a few yards away.

Davis, by his own admission, retreated more and more into himself during the making of The Uncle Jack, obsessively building the model airplanes which form the central motif of the film as he delved into the darker side of his uncle and himself. By his own account, for a long time after the experience he had no desire to direct films, preferring to work as a cameraman. In the last year, though, he had gone back to directing, collaborating with stills photographer Alen McWeeney on a film about generations of Travellers for the Dublin company, Littlebird.

"The Travellers film was bringing me out of my shell a bit, after Jack. I've got to go back to editing that now, this month. I was also just back from Hong Kong, where I'd been as the Irish representative of the European Film Festival, which was fabulous. I was back a week, all full of new life and the Orient and everything."

When he speaks about the devastation, it's almost with wonderment. "My whole archive, basically, is gone. All the out-takes of all the films. The other half of Self-Conscious Over You, which never got made, because I didn't have the dough to finish it at the time. Out-takes from Route 66 . . . A lot of the stuff was in plastic cans, so it's a tricky process getting it out to see if any of it is salvageable. The fire seems to have gone for some things and not for others, but the whole floor was about a foot deep in celluloid. It's not just my stuff - there are loads of generations who have come through the house, and I'm the custodian. Then there's Jack's stuff, the photographs, the films.

Not everything is gone; I've been able to salvage some things." But everything is water-damaged, including the extraordinary model aircraft, with names like the Gazebo, the Rocketeer and Illusions. "I had an archaeological dig going on in the bedrooms for every knick-knack. It's odd; almost as if the most precious things were burnt and the secondary things survived. I had baby baths full of water, with photographs in them stuck together. There's still a lot of stuff I haven't tackled yet."

It is impossible to put a value on what was lost, but the fire also destroyed John's means of earning his living, his camera equipment. "Burning timber fell down into the hall area, where all my camera gear was, and started a fire there, destroying everything," he says. "We'll see what happens, but it's a big problem to get around. I've lost the tools of my trade."

The highly expensive equipment was not insured, although the house itself was, and the reconstruction job has gone out to tender this week. "There's just enough to reinstate the house structurally to something like what it was like," says John, who hopes the family will be able to move back in before Christmas. In the meantime, they're living in short-term rented accommodation.

"It's a terrible experience, like a freight train hitting you head on," he says. "And not just you, your whole family. Everything changes course dramatically. Nothing survives it. In a way. It's been fabulous, because there really have been a lot of people rallying around. For the first two weeks, I was never away from the house, and there was a steady stream of helpers coming down to help me salvage stuff. People who couldn't stay contributed an envelope with a couple of bucks - sometimes more than a couple."

Film editor Se Merry Doyle set up a bank account in Dublin to which people could make donations, and a benefit screening was held in the Irish Film Centre before Christmas, which will help the family get back on its feet again. Other benefits are being planned for Galway, Belfast and Cork over the next couple of months.

The amount of activity reflects the level of respect and affection felt for John in the film-making community and among those who recognise his stature as one of the most important film artists this country has produced. Working in documentaries, he never had the opportunity to make the large sums of money that people associate with moviemaking, but a whole generation of Irish film-makers see him as a mentor and inspiration.

"I got little donations from people I don't even know," he says, in a tone of amazement. "It's humbling, really, to realise that people actually do care."

Contributions to the John T. Davis Fund can be made to ACC Bank. Sort Code 90-90-11. Account No: 62167279