Kevin McCloud returns to Graven Hill in Oxfordshire, the UK's largest mass self-build site, to witness the trials, setbacks and successes of those who are designing and building their own, highly individual homes. First up are Carlos and Maite, who have ambitious plans to build a bold, Spanish-inspired home. But Maite does not just want to live in it, she is also designing it - without any professional qualifications. Meanwhile, co-presenter Natalie Huq follows the birth of a new street in Glasgow, where the local council have given six families an opportunity to construct their own homes on a small plot - beginning with an American-style ranch.