“I thought I was too old for this,” says Les Leahy, 87, as he brandishes a half finished table lamp and a toolbox. “When I first came here, I hadn’t touched my tools in 25 years. I thought I couldn’t use them anymore – I was planning to throw them all away.”

A retired woodwork teacher, Leahy is part of a growing project to improve the mental health of older men through a simple solution: sheds. Three months ago, Les joined a local group in Camden, north London, who meet to mend and create woodwork in a communal space.

Men’s Sheds first started in Australia in 2006 to provide support to men who have experienced mental health issues, problems with the transition to retirement or a lack of social interaction. There are now more than 1,200 sheds in Australia and the scheme has gone global. On Friday, leaders from Australia, Ireland and the UK will gather in Havant, Hampshire, to discuss and celebrate the growth of Men’s Sheds across Britain. A shed is opening every week; there are now more than 100; three in Havant alone.

The first thing I notice about the shed in Camden is that it is not a shed. Yet it certainly looks – and sounds – like one. Tucked away inside a community centre, I hear the saws before I see them. Under low ceilings, planks of wood, reels of tape and tiny plastic boxes full of screws sit surrounded by red wood shavings and half-sanded fruit bowls; evidence of the week’s work. Saws 3ft long hang on cupboard doors and hidden under the worktable are boxes of finished goods: plates, bowls, candlesticks, jigsaw puzzles and “bee hotels” ready for winter. On the walls hang pictures of the group’s communal projects: bird boxes, a gate for the local park and a wooden castle for children at a nearby archery club.

Mike Jenn is carving a sculpture in tribute to The Scream, a painting by Edvard Munch. Jenn is chair of both the UK Men’s Sheds Association and the Camden Town Shed, which he started in 2011 after retiring from a career in the voluntary sector. Although the first Men’s Sheds were launched here by Age UK, Jenn’s project was the first to be led by the community.

“I saw there was a social need and I wanted to demonstrate you could do something about it without money,” says Jenn. The Camden shed costs £5,000 a year to run and is 95% self-sufficient, funded by members’ donations, product sales and by running training for the local community. Almost all of the wood and tools are either scrap that has been found or donated by closing businesses and local people.

“At the beginning, when we needed tools, all it took was four lines in the Camden New Journal. We received six car loads – almost all of it from widows, who wanted their husband’s tools to ‘go to a good home’.”

Jenn thinks the 20 or so people who use the shed, which is open two days a week, roughly fit into two groups – those who come on occasion to get a job done, and those who come regularly for the interaction. He remembers one member who came after experiencing suicidal thoughts.

“He was 54, he couldn’t find a job and his benefits had been cut; he was losing weight. When he came along he just talked and talked and talked – he didn’t do much mending of anything! After eight weeks, he told one of the men who used to be a GP how bad things had become,” remembers Jenn.

According to a 2014 survey by Age UK, more than one million people over 65 in the UK are often or always lonely, an increase of 38% on the previous year. Two-fifths of respondents said that their main form of company is the television.

The project in north London is open to women one day a week, but only one woman comes regularly. Jenn believes that men are less likely to recognise their need for social interaction and are less well provided for by the community sector.

“The offer is wrong and made in the wrong way,” he says. “Men are programmed to believe they can look after themselves. They don’t directly see that their life could be enriched by being with others so they end up hiding away watching TV. If you want a man to do something, don’t ask him to volunteer, tell him there is a problem and it needs fixing.”

Ray Caplan first came to the shed after he was struck by lightning on a golf course six years ago, an accident that forced him to retire from his career as a dentist. He still struggles with his memory but says it is improving. He says he comes for the simple reason that it “is something to do; something to think about”.

Leahy is the oldest member of the group. He lives on his own and has no children. He tries to see his niece once a fortnight. Although adamant that he “absolutely does not believe in the good old days”, Leahy is convinced that people now interact less with their neighbours than they used to. “Forty years ago I knew everyone on my street. Now I don’t know any of the people in my block.”

The UK is among the most socially isolated countries in Europe, according to research published in June 2014 by the Office for National Statistics. Asked whether they feel close to people in their local area, 42% said they did not – the highest proportion after Germany.

Jenn nods: “There has been a huge trend in society in recent decades towards individualism – it’s the result of affluence and commercialisation. Companies want us to live in one-bedroom flats, with our own washing machines and computers. We are boxing off people and sticking them in open plan offices to stare at screens. On the factory floors there was banter, there was interaction. That’s what the men miss here.”

The Campaign to End Loneliness, a national network set up in 2011, believes the issue is a “public health disaster” waiting to happen. Scientific research shows that for older people, loneliness is twice as unhealthy as obesity, as it is linked to high blood pressure, strokes and a weakened immune system.

Laura Ferguson, the director of the campaign, says: “This needs to be a top priority for every local health and care service. We need national leadership and investment on this issue or we may end up pushing already stretched services to breaking point.”

With two hearing aids, Leahy struggles to hear me, but it is obvious he is happy just to talk. “If I didn’t come here I would just be sat at home watching the TV on my own. But here, I have made friends.”