Thirty-two-year-old London architect Seb has the rare opportunity to build his own house in his grandparents' back garden. His ambitious design challenges many of the conventions of traditional construction, from an innovative roof cladding system he devised himself to a structure made from cross-laminated timber panels imported from Austria. For Seb, this is a chance to create something genuinely original, but it's also a huge personal gamble. He wants the house to be built quickly and to the highest possible standards, on a budget of £420,000. On an awkward, tightly constrained site, every penny and every inch of space have to work hard.

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