Kevin McCloud meets Rosa and her partner Craig who are turning a century-old, family-owned, decommissioned steam railway reservoir into a home. Their radical plan to reinvent the reservoir into a unique living space involves punching huge holes through the walls to allow light to flood in, a mezzanine with views across the valley and a concrete extension with four bedrooms. Along the way they encounter a pandemic, numerous money crises, pregnancy and a schedule that grows from 12 months to over three years, is it worth it for Rosa to have the reservoir home she has dreamt of since childhood?

Kevin McCloud returns to Gloucestershire to visit Jon and Noreen who, in 2013, planned to build a three-bed treehouse on a half-acre patch of woodland. Their stacked three box design was to be almost gravity-defying to avoid harming any tree roots and a mirror glass ground floor to reflect the surrounding trees but their £250,000 budget didn't seem to match the project's high ambition. Despite having worked hands-on for long hours with help from friends and family, by 2016 the house was barely ready enough for them to move in and the money had run out with the project not finished. Seven years later, Kevin returns to see their progress.