Dutch architect Christian Müller has overhauled the interior of a chalet in the Swiss Alps, creating a pair of apartments that combine exposed stone walls with raw concrete and distressed wood.

Christian Müller was approached by the two owners of Casa Sur Ual, a 350-year-old house in the Swiss village of Vella, and asked to divide it into two family apartments.

The residence features timber and stone walls as well as a traditional pitched roof with overhanging eaves, and is surrounded by picturesque properties of the same style.

To remain in keeping with its neighbours, this traditional shell was preserved. But inside, existing stone and timber walls have been updated with the addition of new materials and furnishings.

"Villages in the Alpine region are threatened with being turned into ghost towns," said Müller. "This is being caused by a number of factors."

"The present building stock has a large portion of second homes, which are hardly being used."

"The amenities offered do not live up to modern standards and there is preciously little room to build new houses," he added.

The two families each own one third of the property outright, while the remaining third is co-owned. Children's bedrooms, a sauna and storage spaces are located in this part-owned section of the building, which can be adapted as the families' needs change.

"The result resembles something of a three-dimensional puzzle," said the architect. "It is like a scheme of 'pay half, use two-thirds'."

Pale wooden floorboards, integrated furnishings and doors contrast with the craggy stonework and ageing timber. A new cast-concrete staircase provides access to the upper floor in one apartment.

Openings were cut into the tops of some of the original timber walls to produce mezzanine sleeping areas.

Bathroom windows are set behind the building's gappy timber cladding, which allows light to filter into the space.

When not in use by the families, the two apartments can be opened up to each other and rented out to groups of holidaymakers.

"The Alpine regions are an important part of the Swiss landscape and the Swiss artful way of life," said the architect. "The flexible use of existing buildings not only reinforces the local economy but can be, as this conversion proves, ecologically meaningful as well."

Photography is by Susanna von Känel.

Project credits:

Architect: Christian Müller
Local architect: Lukas Egli, Projektierbar
Clients: Kühne and von Känel, Müller and Müller-Züger
Engineering: Ingenieurbüro Walter Bieler