Kevin McCloud is a very busy man. So busy, the only time I can catch him is in a cramped edit suite in a Soho backstreet where he is recording voiceovers for the first two programmes of the new series of Grand Designs. Halfway through our chat, a member of the production team pops in and asks him to re-record several lines in his sonorous actor's voice. Immediately after our interview he must jump in a cab and catch a plane up to Edinburgh to film another episode in the series.
When Channel 4 announced last summer that most of its returning factual series would not be making a re-appearance, Grand Designs was one of the few given a reprieve. It is an enduring favourite with viewers: in 2007 it was Channel 4's highest-rated show after Celebrity Big Brother. Each instalment follows a couple, family or individual as they attempt to build their dream house, thus making architecture accessible to the casual viewer. It charts a series of emotional and often life-changing journeys that can prove transcending or plunge those involved into the deepest despair.
"It isn't just telling stories," says McCloud, "but because the stories fit a corner of everybody's imagination. These are real adventures that people go on, selling everything they've got, taking out huge loans, putting their children in a caravan for a year, making families homeless in order to pursue some irrational dream. Although the vast majority of people are never going to do this, it remains one of those activities we can theoretically all do. I'm not going to sail around the world or make a trip to the North Pole, but I might one day build a house. It does stretch people – it pushes them in the way a physical adventure does."
It is 10 years since filming began on the first series of Grand Designs and McCloud is determined to keep the format fresh. With this in mind, he wants to make fewer programmes and concentrate on unique projects. The reconstruction of a ruined Yorkshire castle in the last series was turned into a 90-minute film, and McCloud is keen to pursue schemes of a similar calibre in the future.
"With any series after 10 years it becomes a machine and you start churning them out, so I think it's important that we keep it fresh. I wanted to develop the narrative style of each differently," he says.
The first show in the new series featured a largely underground house built in a dense urban area in Cheltenham, which attracted a huge number of planning objections. Forthcoming programmes include an architect building his own "beautiful white crystalline box" in Bristol that rarely comes in on time and on budget; a designer building an extremely ambitious house in Bath on the side of a moving hill (with the result that they spend a small fortune on the groundwork); a project in Scotland that is a long sustainable box wrapped into a hill in a piece of open countryside – almost unheard of; and a highly experimental house in Maidstone that may not get finished in time.
The timing is nerve-wracking. When McCloud arrived at the edit suite on the day of our meeting, he was not even sure which of the projects would feature in the second programme. Four out of the eight projects in the new series are uncompleted and when I ask what will happen if they are not finished on time, McCloud replies simply: "I don't know."
The programme also faces many legal issues, builders who go bust, planning officers who intervene – "this series for some reason is messier than others", says McCloud. When things go wrong legally, the Grand Designs team maintains a distance. "We complicate matters when things go legally wrong. We're the first people to get shut out, because we do have documentary evidence on our tape and it may not always be in the client's favour, so it's very important that we stand back and make objective films," the presenter says.
Emotions run high during filming, and McCloud has learnt to switch off like a counsellor. "The great mistake is for me to become friends with people. I get to know people and think 'Gosh, they're nice, maybe I could get to know them a little more and go to the pub, have a drink.'
"But if I see people socially I don't want to talk about work, I want to talk about sport, holidays, cars, landscape, gardening... The last thing I want to talk about is that bloody house, and all they want to talk about is their bloody house."
Finding subjects can be difficult. The production team is "underwhelmed" by people volunteering to appear on the show, and spends a lot of time tracking down projects through Riba (Royal Institute of British Architects), Rics (Royal Institution of Chartered Surveyors), architects and planning departments. Then they go on a reccie.
"I'm not quite sure why people want to do it – maybe because they get a very professionally made home-movie of their build," says McCloud. There is no financial incentive, although there is a small displacement fee, which does not quite cover the cost of builders having to down tools during filming.
"I wouldn't want to be filmed if I were building a house. If I were building a house I wouldn't tell my producer," says McCloud.
But in a way he is being filmed building a house, or 180 houses to be precise. McCloud is the brains behind a project to build two sustainable communities in Swindon. Hab – Happiness, Architecture, Beauty – started life as a television project, but although it is being filmed by Talkback Thames for Channel 4, for McCloud it has turned into something much bigger.
"We started out with me pitching the idea as a television idea, and over the course of two years it changed completely to me setting up a company to build houses in a process which will be filmed by Talkback, but in which I'm not presenting, nor am I narrating," he says.
The project is not just about building houses that are environmentally friendly – "everybody knows how to build ecologically" – but about creating play space, considering how car use can be minimised, and planning local networks of organically grown food. "We use the word sharing a lot," says McCloud.
Later this year, McCloud will also present Grand Designs Live, in which viewers can vote for their favourite newly built, converted or restored homes from a shortlist compiled by the architect Will Alsop, the designer Wayne Hemingway and McCloud himself. Viewers who have recently built or restored their own homes can also enter the competition until 10 February at www.channel4.com/4homes.
A passion for creating beautiful architecture and sustainable communities is why McCloud continues to put up with the hectic Grand Designs filming schedule. "I don't make Grand Designs because I enjoy making television, because I don't really enjoy making television – I stand around in a muddy field all day. I make the series because it does seem to excite people and change their perceptions.
"If we can in a tiny way improve the quality of the built environment, get people to build more ecologically, to think more carefully about the statements they're making in the landscape, to think about their environment and their street and their town – that's why I do it."