Sun Slice House and Spa

Our brief was to extend and restore a Victorian semi-detached house that had fallen into disrepair in South Cambridge. Our clients also wanted to add a new-build outdoor leisure space to the end of their garden to house a gym, sauna and spa area.

Some of the essential requirements were to create a homeschooling area for the client’s children as well as a home working space for the parents, both of whom work from home.

The original house, although in poor condition, had a great deal of character which we wanted to preserve. We worked closely with our clients, running design workshops, building physical and digital models to test spatial ideas, and exploring atmospheres created by different materials. We also produced full scale mock-ups of the various components throughout the process.

We wanted the extension to feel like it was enveloping the existing home, creating a new layer around the older volume, so they could be read together. The eye follows the line of the original house through the skylights in the dining room.

We searched for a material and massing concept connecting the retained parts of the house to the new extension. We achieved this through using Petersen Brick – a slender handcrafted brick which harmonises with the yellow stock brick of the original house. We were also able to salvage for re-use most of the bricks when we demolished the existing outrigger.

Through a series of solar studies and physical models we worked out that if we arranged the skylights on the diagonal running south-east to north-west, we could bounce daylight into the home, without the light blocked by the mass of the existing house.

The two rows of linear skylights create a visual link between the old house and the new extension. A vaulted roof planted with sedum forms the connection between them.

We set a horizontal datum level based on these co-ordinates, with the lower part made in Petersen Brick and the upper levels formed in white plaster reflecting late afternoon light into the house. Time is measured by shafts of lights moving in a pendulum fashion throughout the day.

The single-storey side extension is visible from the main road. The handcrafted bricks echo the tones of the original weathered Cambridge clay brick in the street.

The form of the extension was carefully designed, through our solar studies and models, to create a naturally illuminated north-facing rear extension, maximising light through a rear glazed façade and carefully positioned skylights. Utilising daylight analysis software, we shaped the sloped roof of the rear extension to minimise the impact on the light of neighbouring properties, while maximising natural light internally.

The vaulted roofs are planted with a large sedum bed, allowing views of greenery out of the first-floor windows and encouraging biodiversity.

Design Challenges:
One of the key design challenges was to pay homage to the character of the existing property whilst at the same time bringing it up to date and providing additional space with a sympathetically designed extension and interior that reflected the personalities of the new owners. This was achieved through the use of many visualisations, testing materials insitu and mock-ups of various elements being fabricated.

Project Team:
The professional team engaged to carry out the project had worked successfully on other projects together in the past and this was our third and largest collaboration to date. This ensured the project ran smoothly and was delivered to a high level of finish, despite our office being a fair distance from Cambridge.

Material use:
The existing stock bricks of the existing house were carefully stored during demolition and re-used to construct the new extension, preserving the memory of the old house in the new design. We made the decision not to clean the bricks above the extension and to re-use all the existing sash windows but infill with specially designed insulated glass panels. We retained and refurbished much of the original structure and fabric of the building.

Orientation:
We orientated the two rows of double-glazed skylights to maximise the solar gain and reduce the amount of mechanical heating needed during the day, cutting down on the need for artificial lighting. This made the most of the north-east facing garden facade.

Insulation:
We upgraded insulation levels in the entire envelope, improving U-values by using insulated plasterboard to the walls and a combination of rigid insulation and Rockwool to the floors and roof. All windows are high-quality thermally broken double-glazed argon gas-filled units. We used careful detailing to minimise heat loss through the envelope.

Energy use:
Underfloor heating runs throughout the house with every room being its own zone. We used a central MEV unit, plus 3 x dMEV fans, for ventilation, allowing for a constant feed of fresh air from the outside. All the heated air is recycled back into the house before it is exhausted outside. We used low-energy LED lighting wherever possible, as well as eco-rated appliances and an eco-rated boiler and hot water storage tank.

Landscape measures:
In the centre of the garden, there is a vegetable garden next to a natural meadow. The meadow planting creates a foreground screen to the new-build outbuilding made of charred timber. Both the extension and the new-build spa have green roofs promoting biodiversity. We provided an allotment space and greenhouses in the garden for the clients to grow their own fruit and vegetables.
The entire property was carefully considered and through working with landscaping designer, Jane Brockbank we were able to make best use of the garden which includes a lawn, greenhouse, allotments and a meadow garden.