British practice Ström Architects has updated a period property in Surrey, England, with a large yet discrete extension built from fair-faced concrete and lime-washed brick.

The project, called The Pines, rationalised the floor plan of the traditional-style house and created modern facilities including a combined kitchen and dining room, a home office, and a gym and sauna.

Ström Architect's design provides these new spaces in a contemporary single-storey extension that is markedly different from the existing architecture but sits comfortably alongside it.

"We did not want to detract from the overall scale and massing of the main house, which is substantial," explained architect Magnus Ström, founder of Ström Architects.

The clients are a couple with three grown-up children. Like Ström, they are originally from Sweden, which informed the choice of light-toned building materials.

The pale concrete and brick were designed to complement the existing palette of white-painted pebble dash, black-painted timbers and terracotta roof tiles.

"We wanted some difference," Ström told Dezeen. "The palette complements the existing, yet has a Scandinavian touch."

A key aspect of the brief was to bring in more light and create a better connection with the garden. The clients were also keen for the main living spaces to be separate from work and utility spaces.

The new layout relocates the garage to the south of the property, closer to the entrance, freeing up space at the rear for an L-shaped extension that surrounds the swimming pool.

The new kitchen and dining space is located in the centre, set 60 centimetres lower than the main house, with sliding glass doors that lead out to the poolside terrace.

"Lowering the floor allowed us to increase ceiling heights and step the extension along with the natural, gentle slope of the site," said Ström Architects.

New doorway openings on either side of a retained fireplace create a natural flow between the kitchen and a snug located behind.

Kitchen cabinets and appliances are all contained with a storage wall, for a clean aesthetic. One of these white doors also conceals the entrance to the corridor leading through to the new office, gym and sauna.

The interior design of The Pines echoes the pale, warm tones of the exterior with details including oak cabinetry and pale porcelain floor tiles.

The result is highly minimalist, much like previous Ström Architects projects such as Island Rest, a holiday home in the Isle of Wight, and The Quest, a contemporary retirement home in Dorset.

"The remodelling completely changes the feel of the house and invites light into the spaces," added Ström.

"The garden, which was redesigned as part of the works, is now an integral part of the design."

The photography is by Richard Chivers.