Construction began last week on a partly below-ground 278m² house in Hampstead, with plans to feature a basement gym and cinema room.

The 3000sqft new build at 30a Thurlow Road has been designed by Square Feet Architects for a music lawyer and his family and replaces what was a dowdy bungalow with a 3-storey house.

The architect’s decision to build partly underground was prompted by a lack of space due to nearby buildings.

Daniel Leon, director at Square Feet Architects said: “The site is in a conservation area and close to adjacent buidings so to built tall was not an option without affecting the neighbours daylight and privacy. With the necessary increased densification of London, expanding downwards in a responsible way, is a practical option.”

A combination of rough sawn stained timber, polished plaster and large expanses of retractable glazing make up the palette of materials. Internally, exposed concrete and timber will be used.

According to the emerging practice, the “unquestionably and unapologetically modern” home follows in the footsteps of the many “iconic one-off” Modernist homes in the area, including Wells Coates’s Isokon flats, Max Fry’s house in Frognall Way and Michael and Patty Hopkins’s own home in nearby Downshire Hill.

Although building underground is “twice as expensive as building above ground” according to Leon, this project comes at a time when partly below-ground houses are becoming more commonplace, especially in London.

Leon said: “In London it’s so commonplace that many contractors are well versed in the suitable methods of below-ground construction, both with regard to structure, and understanding and managing the underground water levels and flows in a correct manner.”

“But its not new of course - how many Victorian houses have cellars that have been converted into kitchens or playrooms? Maybe we just reinventing the wheel?!” Leon added.

Although the project is inspired by many of the Modernist examples in Hampstead, it also benefits from Modernist architecture from across the pond.

“We’ve always been interested in the Modernist houses in Los Angeles and California, such as the Richard Neutra and Rudolph Schindler style houses, so it’s taking that and bringing it in with an appropriate and sensitive view to London and Hampstead.” .

Despite struggling to obtain planning permission for the basement design initially, Leon said: “We are extremely excited to finally see this project materialise after a long gestation period, but soon we will see the fruits of our labours. The house will look great we think and hopefully, in due course, add to the panoply of Modernist classics in Hampstead,” he added.

“I think architecture like this helps to keep Hampstead vibrant. It’s a beautiful place with a village feel to it but these new modern additions keep it exciting and relevant.”

Work is expected to be completed in September 2018.