Tracy Fox and husband Steve want to build an "urban shed" featuring two studios, three bedrooms and a double-height space with a walkway, made out of industrial-style materials including corrugated cement fibreboard and 20ft panels of polycarbonate sheeting. Having discovered an old milk yard tucked away behind some flats and shops in south-east London, their long-held desire to build a highly unconventional family home and workspace begins. But their choice of unorthodox materials proves challenging and costly.

Kevin McCloud follows software executive Andy Bruce and garden designer Nicki Bruce, who are planning to build a "floating" house on the River Thames, which would be the first of its kind in the UK. Their architect has come up with an ambitious, experimental design that would see the whole property magically rise up with the flood waters. However, no one knows whether it will work, and the project soon becomes bogged down in the logistical challenges of bringing to fruition such a complex structure on a small island that is only accessible by a narrow footbridge.