Andy and Nicki Bruce try to build an experimental flood-proof floating house on an island in the River Thames. But building such a complex design on a site with limited access is not easy. Andy and Nicki Bruce's amphibious house, the first of its kind in the UK. Their architect has come up with an ambitious, experimental design that has never been tried on a river bank in Britain and no one knows whether it will work. The Bruces decide to build on a site on a small island in the river. But it's not long before the project becomes bogged down in the logistical challenges of building such a complex design on a small island that is only accessible by a narrow footbridge.

Peter Berkin and his wife Chard have decided to build a new home at the bottom of their garden. Problem is, right from the start they can't agree on any part of the design - even the basic shape. Peter wants the new house to feature a workshop where he can build a plane. He wants the house to be round. Chard however wants it to be square and practical. Peter aims to spend pounds 400K, Chard wants to keep the budget around pounds 200K. With Peter building as much of the house as he can himself, helped by his mates, and Chard taking control of the money and schedule, it looks like a recipe for disaster.

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.

Kevin McCloud returns to a remote part of France and a restoration project of a dilapidated manor house started back in 2003 by Denise Daniel and Doug Ibbs. When Denise Daniel and Doug Ibbs gave up everything in the UK to start a new life in a remote part of central France, they couldn't have known what was ahead of them. Most people would have regretted falling in love with a massive, dilapidated manor house with just four crumbling walls and half a roof, but not Doug and Deni. This impressive, extraordinary and utterly determined couple rolled up their sleeves and slogged away day and night, doing everything themselves, year after year, until slowly but surely they created a magnificent edifice out of the ruins they bought off the internet.

Rob Hodgson and Kay Ralph plan to build an architectural monument high on a cliff top. They want to build a sleek glass-fronted house inspired by the cliff-top villas of California. Their plot overlooks a beautiful National Trust beach in North Wales, but to have their jaw-dropping panoramic views will mean taking the biggest gamble of their lives. Access will be incredibly difficult and expensive because of a low bridge over the narrow track to the site. Erosion specialists predict their stunning new home could one day fall into the sea. Prohibited by the local council from reinforcing the cliff face, they decide to build anyway, believing at least the house will outlive them.

Rebecca Sturrock has returned to her family home in Cornwall with her partner Gregory Kewish and a highly ambitious plan. Together they will transform a small, damp, single-storey bungalow into a cutting-edge home on a budget of just pounds 80,000. With rain and wind hammering the site, however, it soon becomes dangerously clear they may have bitten off more than they can chew.

Tracy Fox and husband Steve want to build an 'urban shed' out of industrial materials in an old milk yard in south east London. But the choice of unorthodox materials proves challenging and costly. The build will feature two studios, three bedrooms and a double height space with walkway, with materials including corrugated cement fibre board and 20 foot panels of polycarbonate sheeting. Work on the build stalls until they meet Romas and Remi, a young firm of builders, who boldly decide to take on the challenge of building it for just pounds 300k.

Kevin McCloud returns to Devon for an update on one of the most inspirational builds he has ever witnessed. Marine Captain Jon White and wife Becky were living happily in a small cottage in Devon when in June 2010, while serving in Afghanistan, Jon stepped on an improvised explosive device. Jon lost both legs and his right arm. Every part of his and Becky's lives had to change - starting with where they could live. Their architect came up with a cutting edge, semi open plan building with a dramatic wing-like-roof; but crucially it was to be without noticeable adaptations for Jon's disabilities. It was an ambitious design, and despite the help of a number of military charities and a capable team of builders, Jon was already under severe pressure to finish the house, when news came that Becky was pregnant. Has the new home proved as enabling for Jon, Becky and their expanding family as they'd hoped?

Natasha Cargill wants to build a home shaped like two enormous periscopes in rural Norfolk. But a limited budget and tight planning restrictions start to take their toll. To get planning permission for her build, Natasha Cargill has to ensure not only that the materials used are sustainable, but also agree to measure the amount of diesel used to deliver them. The planning controls are so rigid in fact that even details like the type of portaloos the builders use and the size of her bath have to be monitored. Natasha has just pounds 330k to spend on construction and just six months to complete.

Kevin McCloud returns to a unique Japanese-Welsh fusion home in the Wye Valley to see how the improvised building weathered one of the wettest winters on record. Tamayo Hussey has missed Japan ever since she moved to the UK 15 years ago with her husband Nigel. To stave off the homesickness they decided to transform their home into a one-of-a-kind Japanese house - complete with Japanese roof bath, tatami room and paper sliding walls. Kevin finds out if it has brought the calm and tranquillity Tamayo remembers from her childhood in Japan.