Kevin McCloud looks at the transformation of a derelict mill cottage in Northumberland into a contemporary family home, the longest-running project ever featured on the programme. Stefan Lepkowski and Annia Shabowska began work in 2006, and their ambitious plans involved restoring the Georgian building, reconstructing a watermill and adding a steel-and-glass atrium, but their budget of £250,000 was completely inadequate.

Paul and Penny are tearing down their million pound home in south London to build a contemporary mansion. But the challenge of building a complex home soon starts to bite.

Kevin follows the progress being made as Tim and Philomena O'Donovan, convert a lifeboat station in Tenby, Pembrokeshire, into a contemporary home.

Kevin McCloud follows the conversion of a large, Grade II-listed timber-framed barn in Essex into a family home and work-space by artists Freddie Robbins and Ben Coode-Adams. Their plans involve few interior walls to display their collection of toys, but at seven times the size of an average three-bedroom house, the transformation of the 500-year-old building proves extremely challenging.

Kevin McCloud meets estate manager Ed Waghorn and his wife Rowena, a couple living an almost self-sufficient life with their four children on a smallholding in Herefordshire. They have been constructing a timber-framed house using recycled materials, wood from nearby forests and stone from around the site, but as construction becomes a way of life for Ed they seem to have lost sight of their goal.

Ever since he was a child, stonemason Adam Purchase has loved the old silver mine engine houses that characterise Cornwall's landscape. When he and his partner Nicola Brennan chanced upon a dilapidated Grade II listed engine house with planning permission to turn into a home, it was a dream come true. But converting this important historic ruin into a place to live was never going to be easy. The building itself was little more than a shell, with crumbling plant-infested walls and no roof, windows or floors: a challenge for even the most experienced builders like Adam. Meanwhile the banks refuse to lend them more than £100k, which Adam and Nicola both know is barely enough to get them through. Still, driven by their passion for old buildings, Nicola agrees to support Adam while he takes a year off work to complete the project.

Claire and Ian try to build a home big enough for a disco on a small plot at the end of a London mews. But as angry locals begin to object to their plans, things start to go awry.