Kevin McCloud follows plumber Jon Martin and ceramicist Noreen Jaafar as they transform a neglected half-acre site in Gloucestershire. However, they are unable to cut down the 27 protected trees on the plot, so their solution is to build a big, modern treehouse with stilts screwed into the earth and balconies that will have views for miles.

Kevin McCloud follows Matt and Sophie White from Sussex as they build a giant family house of fun for themselves and their children. Going against the norm of designing a serious and practical home, the couple's property features a revolving bookcase door, secret dens, hiding places, one-way mirrors, and a fireman's pole. Matt uses a steel frame system to allow them to change the layout of the property, and other changes include amending the window shapes and sizes, and adding a half floor to create a James Bond room.

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.

Kevin McCloud meets Michelle Parsons, an artist and teacher who decided to seize the day and build her own private hideaway in a woodland environment in Essex after she recovered from a serious illness. Together with her architect husband David, Michelle planned to construct a sleek, black-clad, three bedroom house complete with an art studio. However, torrential rain and a potentially disastrous gas leak stalled progress on the build, and as construction gets under way, Kevin wonders whether the couple's decision to eliminate windows on two sides of the property may leave them living in a gloomy bunker.

Bolton-based bricklayer Paul Rimmer, who has spent his career restoring and renovating Victorian terrace houses, sets his sights on constructing a state-of-the-art home on a budget of £350,000. However, instead of using the construction materials he has spent the past 40 years mastering, he has opted to build his new home from wood. Roping in his wife Carol, daughter Abby and a selection of favoured workmates, Paul and his team begin work on the ultra-modern, five-bedroom build, and Kevin McCloud reveals how extreme weather, exhaustion, and rapidly dwindling funds place the entire project in jeopardy.

Simon and Jasmine Dale take on the challenging task of building a 21st-century, low-impact three-bedroom family home with a budget of only £500. As part of a pioneering, government-backed, sustainable village called Lammas, the couple must adhere to their fierce planning conditions of self-sufficiency or risk losing everything.

Kevin McCloud meets Mark and Candida Diacono, who have set about building a home in the shape of a plough on their 17-acre smallholding in Devon. With its complex curved roof, timber-clad exterior and steel-framed working barn, the ambitious project presents a unique technical challenge for a local builder and his team of employees, and the task proves even more intimidating when considering Mark and Candida hope to complete work on the build within seven months.

Stuart and Rosie Treasurer from the Wirral plan to transform a small bungalow from a 1960s dormer into a slick piece of 21st-century architecture. The couple decapitate the building and balance a new floating timber box on top to create five bedrooms, spending as little as possible on plumbing, electrics and insulation, but stress levels spiral when neighbours grumble at the ultra-modern creation.

Kevin McCloud returns to Somerset to see Ed and Vicky Versluys and their cowshed conversion. Within two years of meeting, Ed and Vicky had got engaged, abandoned their city lives, and bought an ugly, derelict 1940s cowshed. They decided to project manage and convert the cowshed into a home and business with the help of just one young builder and what they could learn from the internet. With a wedding to plan, no access to mains power or water, it's no surprise that they didn't manage to finish within their ambitious eight month schedule. A year after his last visit and with the house finally complete, Kevin finds out what it's like living in an off-grid home designed for animals.