Extending upwards or out into a garden is the usual route to adding more space to a property. However, in the case of this 19th-century home in a conservation area of Hampstead Heath, London, the solution required thinking outside the box and going underground.



“The client certainly had ideas about what they wanted the building to contain, but it was left to us to arrive at the layouts,” says David Snaith, co-founder and director of STAC Architecture, who was brought on board to modernise, restore and extend the house. “The key to unlocking the site was to remove the 1970s link building between the main house and the coach house and put this below ground. This doubled the size of the garden for their young children and created a new cinema space, extra bedroom and storage at basement level.”