“In the very first series of Grand Designs we only made eight episodes, and frankly I was surprised when we got into double figures, never mind reached the hundredth programme,” says Kevin McCloud, when asked how it feels to have spent the last 13 years on buildings sites in Britain and Europe.

“So much work goes into each programme – more than 200 hours of filming on location, then many more hours writing and editing. I thought by now we would be running out of ideas, but I’m surprised all the time. I’m fascinated by the fact that everything is so different.

“The biggest change I have seen over the years is that people’s ambitions are much less grand. Because they can’t spend their way out of a hole the way they could before the recession, it’s been good for their ingenuity, and ultimately that makes good television. So I think this is our strongest series yet. I’m really excited.

“Television is a short-term world, but we plough on. In the lifespan of Grand Designs we’ve had 24 directors, five series producers, three executive producers and we’re on to our sixth commissioning editor at Channel 4. I’ve been on the back burner all this time, in the shadows, under trees, pootling along. I’m very happy to continue to do that.

“It’s not a job; it’s a way of life for me. It’s what I do.

"Here are my favourite Grand Designs..."

The 100th house, Lambeth Workhouse Water Tower, London, 2012

A derelict, Grade II nineteenth century water tower that was built for a former workhouse and infirmary in 1877. The tower is 99ft tall with 5ft-thick walls and topped by a huge steel water tank.

“How would I describe this? A domestic version of the Tate Modern meets Venetian Gothic, like the tower of St Mark’s in Venice or the law court in Mumbai. The tower belonged to a workhouse where Charlie Chaplin had once lived, and it combines everything we’ve ever done into one project. It’s about conservation versus new build, and the junction at which they meet. Half the film is about the restoration project, because it was in a state of advanced dereliction and disrepair, while the other half is about the new build that sits beside it.

“The tower will house four bedrooms and 360 degree views across London, with a lift shaft alongside the tower, while at the bottom is a new, cube-shaped modern living space.

“It all comes together in the way the guys – Leigh Osbourne and Graham Voce – treated the water tank at the top of the building. It’s a big, black, windowless box sitting on top of the gothic tower. They cut big holes in the walls, into which they put black glass. I think it’s been very successful. From the ground you can hardly discern any difference.”

The Woodsman’s Cottage, West Sussex, 2003

Using techniques harking from medieval times, woodsman Ben Law built a sustainable house using materials growing in his surroundings.

“Over the years I’ve had favourite people, favourite builds and favourite films. Sometimes you get a lovely confluence where all three come together and I think Ben’s project - a sustainable house using materials growing in his surroundings - fits that. His is a lovely, light-filled home that is beautifully made. He found the process taxing, but not horribly stressful. The only jeopardy in that project was the approach of autumn and the worry that the weather might turn.

“I’ve been back twice and I think we could easily film a third revisit. I’ve watched his life change because of that house. He’s running courses and has written a book, all grown out of that project. It’s wonderfully empowering.

“My shed project was very much inspired by him. I bought a piece of land in the Mendip Hills in Somerset, a couple of acres, upon which I built a shed made from two oak trees that I felled. It’s kind of Ben Law meets Top Gear. I made a beautiful chair from an old tractor and skin from a culled deer, a stove out of an old jewellery safe and a willow bed. I love it. I get to spend my weekends there.”

“The house was always designed to be flexible and adapt to changes and the need for family," explains Ben Law. "It changed when I built an extension for my children, but it has stayed the same since. My eldest son Rowan, 16, has spent the last two years living here, too, so it has had to work for teenagers as well as toddlers.

“I knew that Kevin had been affected by the woodland house, and during the winter following filming he planted a lot of trees. I usually see him at Grand Designs Live each year and follow his building projects with interest. I've had quite a few comments from viewers of his current Man Made Home programme that he is starting to dress like me - leather cap and waistcoat! I guess I should take that as a compliment!”

The Modest Home, Woodbridge, Suffolk, 2010

Lucie Fairweather and her husband Nat McBride wanted to build a low-impact eco home for their family.

“Sadly, Nat died during the making of this film and Lucie was left to continue on her own. What she did was build a downsized version of the original. Their architect, Jerry Tate, was a great friend of Nat’s and I thought what he produced was done out of love for him. What Lucie ended up with was a beautiful, three-bed, modern, sustainable chalet bungalow. How often do we get to see that?

“Over the years I’ve seen sustainability become much more ingrained in the building process. Whether you’re remodelling an existing house or building from scratch, you have the same aim – to immunize yourself from heavy bills and make the house low-cost to run. It used to add 25-30% onto the cost of building, but it’s very easy now.

“When I encounter houses with seven bedrooms, a Pilates studio and a home cinema I slightly glaze over. What I love seeing is a relatively modern house; not hugely expensive but typical of houses we live in, that are a wonderful new exploration of the form. That’s when it really takes off for me.  And Lucie’s modern bungalow is a perfect example of that.”

The Eco Arch House, Weald of Kent, 2009

Architect Richard Hawkes built a cutting edge home with green technologies for himself and his wife Sophie, that would provide almost all the energy they required.

“This house had an unusual brick arch that formed the backbone of the building. It was so elegant and clever, a joy every time I visited. Richard was determined to use the minimal amount of material and keep it very simple and super ecological. The idea that such a simple brick arch could support such a load was inspiring and an example of how ideas continue to change. When I look back over the many episodes of Grand Designs, I realise they’re like historical documents, charting the progress of ideas and progress.”

The Contemporary Cedar Clad Home, Stirling, 2006

Theo and Elaine Leijser built a three-story, cedar-clad home on a plot overlooking the picturesque Campsie Fells.

“What a privilege it was to film that episode. It was the perfect example of a modest, clever, beautiful, sustainable house with a very clever device. By sticking a big box on the front of the building, it meant that you couldn’t see to the left or the right very easily. What this did was direct your view to the Campsie Fells, which you could see brilliantly, but you didn’t notice the road.

“When I see a new idea like that it thrills me. I love the expedience of it.”

The 14^th Century Castle, Skipton, North Yorkshire, 2007

Francis Shaw and his wife Karen fell in love with the crumbling ruins of an ancient building and vowed to breath life back into its walls.

“This was a mix of conservation, repair and theatrical reconstruction. What was lovely was following the process. It took four years to film and over that time it marked how English Heritage’s attitude changed to such restorations.  What Francis achieved championed an example of a mixed approach and at the end of the project English Heritage produced a very important document on conservation principles and how we should look after old buildings. It marked a change in attitude.”

The Lime Kiln House, Midlothian, 2008

Richard and Pru Irvine wanted to build a modern house on an industrial site, but were told it had to blend in with the old limekilns.

“In every series we have a nod to the white box, which we think of as being very modern, in spite of the fact that as a concept it is over 100 years old now. It’s almost become a stereotype.

“I have a fondness still for a long box that has been rendered in off-white in Scotland. Richard and Pru wanted a modern building, but it had to fit in with its surroundings. So the house had a hat made out of wooden shingles, rather like a lid, but still achieved the purist white crystalline thing. I liked that, and the way it nodded to the vernacular. It was a resounding happy medium.

“I like how we have moved away from building large boxes to a softer, more contextual approach. People are now veering towards the vernacular, using the materials common to the area in which they are building.”

Two Italian houses, Tuscany and Puglia, 2004

Two very different builds: a thousand-year old castle and a derelict olive farm.

“Both episodes highlight the bizarre rituals of Italian planning. When I saw the castle proposal I thought, this is going to be good, and it was. Janne Hoffe-Tilley and Howard Smythe wanted to build their dream home in Italy and a dream home it was – elegant and luxurious. By contrast, when I saw the Puglia project it looked so minimal I questioned whether we should film it. David Westby and Leonie Witton wanted to build an artists’ retreat themselves on a budget of £25,000. But the level of craftsmanship on very little money was compelling to watch, and it remains one of the viewers’ favourites and mine.”

Don't miss Grand Designs' 100th property - tonight at 9:00pm on Channel 4