Kevin returns to Devon to meet Kevin McCabe, who wanted to build one of the biggest houses ever on Grand Designs, out of mud. Seven years after it began, the cob castle is complete.

Kevin meets a couple converting a listed mini-castle in Buckinghamshire into a family home. The Saxon burial ground the folly is built upon throws up some macabre surprises.

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.

Harry and Briony are relocating and building an American modernist house inspired by 80s teen comedy Ferris Bueller's Day Off. The project is big and proves challenging.

Steph Wilson and husband Alex try to build a contemporary farmhouse on her grandfather's old farmland. But lack of money leads to a long spell in a caravan and a total re-design.

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.

Deep-sea diver Adrian Corrigall and wife Megan want to build a concrete family home that Adrian hopes will prove the ultimate 21st-century country house.