In Devon, Joe and Claire hope to create 'one of the greatest homes on the planet' that looks like a huge piece of art. But from the start, the expensive build faces mind-boggling problems.

Kevin McCloud meets master carpenter Olaf, who is facing the biggest challenge of his career - creating an oasis for himself and partner Fritha on a small slice of land in West Sussex, which happens to be surrounded by a mainline railway and a busy A-road. Not only that, but half of the plot can't even be built on due an underground mains sewer. All they're left with is a very small triangle on which to build their future life together. With £190,000 in the bank, Olaf and Fritha must use all the ingenuity they can muster to make their triangular three-bedroom house come to life.

Kevin McCloud meets architect Iain and his wife Jenny, who intend to build an enormous black minimalist house right in the middle of a 19th-century Scottish country estate. Their grand vision also involves connecting the new rectangular block to a dilapidated gardener's bothy - and the neighbours are watching.

Kevin McCloud meets widowed teacher Gretta, who is making a fresh start in rural Cambridgeshire with a Malaysian-inspired burnt wood and glass home being designed by her nephew Carlos and project managed by her brother-in-law Fernando - despite his lack of building experience. However, as site clearance begins, so does the Covid-19 pandemic - and family harmony is tested when an apple tree much loved by Fernando is condemned for removal by Gretta.

Kevin McCloud meets architectural designer Dan and interior designer Nina, who want to build a sleek, unique family house. But the plot they have bought, near a beautiful estuary in West Sussex, is dominated by a swampy pond that they are unable to fill in. Instead, they plan to make it central to their design, turning the pond into a biodiverse waterscape, and then floating their house above it. It's a challenge for anyone - but to save money, Dan is doing it largely himself, despite his limited experience with new builds.

Kevin McCloud meets Cumbrian couple Rob and Ruth, who have bought a 200-year-old former blacking mill and plan to slot in an entirely new, timber-clad structure within its walls, giving the impression that it is peeping out from the original ruins. But the original building is a scheduled monument and Historic England inform them it is too dangerous to repair, giving them no choice but to painstakingly rebuild the ancient mill around their new structure.

Kevin McCloud follows the progress of ex-advertising man Geoff, who is selling his luxury villa in Spain and moving into a caravan while he project manages the construction of a dramatically cantilevered steel-framed house on the Essex coast, costing a total of £700,000. But after the anchoring steel has been drilled into the ground, he runs into the double trouble - Covid-19 and a collapse in the Spanish property market. Will he ever finish this complicated - and expensive - construction?