Kevin McCloud follows the progress of 37-year-old Angelo Mastropietro, as he transforms a damp, dark and abandoned cave in Worcestershire. Having recently been diagnosed with multiple sclerosis, Angelo wants to create a retreat to help him cope with the news and become a 21st century caveman. He has a budget of pounds 100,000 and plans to almost single-handedly carve, cut and drill into the hillside to make the cave comfortable for contemporary living. However, there is no manual for a project of this kind, and the unique challenge soon becomes an obsession.

Identical twins Nik and Jon build near identical houses in Sheffield. Raised on steel stilts, these two extraordinary properties pay tribute to Sheffield's industrial past.

A young farmer and architect in Northern Ireland hopes to make a home out of four large shipping containers welded together to form a giant cross. Patrick Bradley has come up with a pounds 100k house design to be built out of four 45-foot shipping containers, welded together to form a giant cross and cantilevered over the top of a stream at a beautiful secluded spot on the family farm. His mum is hoping his new home will get Patrick a girlfriend. But his tiny budget is soon under threat.

In 2019, Olaf and Fritha set out to build on a tricky slice of land in West Sussex, boxed in by an A-road and trainline. Kevin McCloud returns to see how their triangular triumph is faring.

Kevin McCloud meets Clinton Dall from Sussex, a self-made businessman and father of four aiming to build one of the largest homes ever featured on the show. Dall wants the end project to be perfect - from the finish of his mirrored cruciform steel columns, to how the floor tiles line up with the dining room table, and is willing to spend whatever it takes to achieve his vision. However, the construction represents a huge risk, as down one road lies abject failure and financial ruin, while down the other, is the creation of something sublime and almost heroic.

Boat enthusiast James Strangeways invites Kevin McCloud to survey progress on the construction of his new home, which his architect nephew Ben Hebblethwaite has designed to be as 'un-houselike' as possible. James has spent the past 35 years travelling the canals and waterways of Britain, and despite never liking houses, has decided now is the time to put down roots on dry land. Ben hoped a home standing on stilts above a marsh, and incorporating ship-like qualities such as a keel-shaped roof, will be enough to satisfy his boat-mad uncle. However, Ben's contractor goes into liquidation a few months into the project, taking pounds 87,000 of the pounds 300,000 budget, and when James decides to make a few tweaks to the design, alarm-bells begin to ring for the young architect.

Kevin McCloud follows the progress of teacher Michele Long and architect Michael Howe, who want to restore and transform a 100-year-old blacksmiths in County Antrim near the coast of Northern Ireland. With virtually no practical experience, Michael wants to do as much of the project as possible by himself. However, the weather on the coastline is fierce, and the freezing weather coupled with a tight budget of 150k means the build is stretched from one to three years.

Kevin McCloud follows the progress of private chef Ed Versluys and pilates instructor Vicky Anderson, who want to convert a concrete cowshed in the Somerset countryside into a three bedroom home. With the help of one young builder and the knowledge they can learn from the internet, the couple plan to project manage the conversion themselves. However, they have only eight months and a budget of just over pounds 200k to make a warm and comfortable home with straw bale walls and wide expanses of glass.

Kevin McCloud follows the progress of Stephen Yeoman and Anita Findlay, who want to build a cutting-edge, post-industrial house covered in rusty metal. However, their prominent riverside plot in the traditional and architecturally conservative area of South Downs means everyone will be watching. The project proves to be a real rollercoaster when the fitting of the rusty steel cladding goes wrong, cash flow problems threaten to bring work to a halt, and the couple announce that a baby is on the way.

Following the work of Ed and Rowena Waghorn as they continue to build a handcrafted, five-bedroom house on an eight acre smallholding in Herefordshire, 10 years in the making. Progress on the build was slow as Ed decided to do most of the work himself, and after four years the house was still a shell. Now, years later, is it possible this house may finally become a medieval masterpiece?

In a leafy spot in south west London, Elinor and Born want to build Britain's first 'healthy' house, to alleviate their sons' life-threatening allergies in a race against time.

Richard and Felicia almost singlehandedly turn an underground water reservoir in the Humber Estuary into a family home. It's an epic task. And then a life threatening illness strikes.

After recovering from leukaemia, Toby is driven to build a complex home around an old oak tree. But can he balance high architecture and health with a comfy family place?

On a nostalgic revisit to the first ever Grand Design, from back in 1999, Kevin finds out if Tim and Jules are still flying high in their timber-framed home on the cliffs above Newhaven

In November 2001, Tom and Judy demolished a bungalow and started building an infinitely more ambitious house. Designed on different levels, with glass walls and exposed steelwork, it was to be a miraculous piece of engineering, giving the couple and their two young children a beautiful, technologically advanced home. Tom appointed himself project manager—a job that proved to be more challenging than he had expected. Grand Designs 3 followed the first 16 months of the build. As Grand Designs 4 goes on air, how close is it to completion?

Kevin McCloud marks the 100th episode with one of the programme's most ambitious projects to date. Leigh Osborne and Graham Voce want to convert and extend a landmark 150-year-old water tower in central London into a luxury home. Grade II-listed, derelict and with 6ft-thick walls, it's a huge challenge for the pair, who also plan to build two structures at the base - a lift shaft connected by a series of glass tunnels, and a modern living space. The result will be a four-bedroom property over nine floors, complete with a room at the top offering spectacular 360 degree views across the capital.

Kevin McCloud meets Tom and Danielle Raffield, whose lifelong passion has been steam-bending wood. They've used the technique to create extraordinary furniture and lighting, but now plan to use it on a larger scale. In an attempt to escape the confines of their tiny gamekeeper's lodge, they have decided to build a wavy wooden house in South Cornwall, completed with curved cladding, twisted furniture and interior walls covered with weathered timber. With a £100,000 budget, the pair have decided to do a lot of the building themselves, and Kevin is on hand to discover whether they're up to the challenge.

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The 1930s derelict water-works Chris and Leanne fell in love with was huge and its design had clearly been inspired by Gilbert Scott's Bankside power station, now better known as the Tate Modern. But nothing would deter the couple. 'We looked at it,' said Chris, 'and saw our home.'

Kevin meets a pair of civil-partnered university professors, Celia Brackenridge and Diana Woodward.  They have enlisted the services of industrial designers who have developed a new computer-assisted method for cutting precision-engineered building blocks, however although the technique may be clever, its creators have never created a building before

Justin plans to restore a neo-Gothic cemetery keeper's lodge and convert its toilet block into a luxury extension complete with a moat and swimming pool. But can he keep his budget under control?

Kevin McCloud meets Greg and Georgie who are taking on the highly ambitious task of converting a dilapidated, 35-year-old barn in Kent. The build will be a huge challenge involving the painstaking conservation of the existing rotten structure, building a new two-storey internal steel frame and recycling everything they can to stretch their £250,000 budget.

Master carpenter Olaf faces the biggest challenge of his career: creating an oasis for himself and his partner Fritha on a tiny slice of land in Sussex near a mainline railway and A-road

Furniture maker Lucinda wants to construct a beautifully crafted, two-storey, highly insulated timber home in the woodland of South Herefordshire on a very modest budget, and without using heavy machinery.

Does good architecture have the power to heal? Kevin revisits Elinor and Born, who built a clean-aired, hypoallergenic house, motivated by their two boys' extreme allergies.