Covert House

Deborah Saunt and David Hills of DSDHA set out to design their family home as a testbed for their ideas on sustainability. Their experiments, carried out under restrictive Conservation Area planning conditions, resulted in an unorthodox, semi-underground house that challenges what it means to design a contemporary domestic space close to the city centre.

The project began when an old house with a large overgrown garden were purchased in 2007. Two applications and an appeal later, in 2010 DSDHA won permission to build. Covert House is indeed a case study on the potential for unlocking backland sites and create architectural opportunities that might ease the urban necessity to build more homes in cities.

The two-storey house is a box-like form of two colliding white cubes, which is entirely shielded from street view, set behind a terrace-lined residential block in Clapham, south London. Due to planning constraints the house was limited to a single-storey height, as such DSDHA decided to partially bury the structure within its garden plot.

The exterior presents itself as a low-rise, lightweight architectural element. It is clad in white render with chamfered mirror reveals to the openings that camouflage the house within its verdant surrounding, while simultaneously dissolving the bulk of the walls. By contrast, the interior appears as a two-storey solid volume, whose exposed concrete walls and ceilings are mostly left raw and unfinished.

The pavilion-like exterior belies its spacious interior, resulting from generous ceiling heights and an open-plan ground floor that distributes the kitchen as well as the dining and living room areas. These spaces are flooded with light and connected to the outside through skylights above and full-height glazing that carves out a sequence of varied perspectival openings onto the garden. The brightness of the interior is further enhanced by the polished white resin floors that bounce light upwards onto the poured concrete soffits.

On the contrary the lower level is embedded in the earth and hardly visible from the exterior, yet visually connected to the garden from every room via two courtyards. This floor, accessed via a white concrete stair, is divided into smaller private bedroom and bathroom spaces, which can all be all entered off an informal living room area.

The challenge with Covert House was that of building next to a very old house close to other homes, on a site that had been completely overgrown with self-seeded trees. As such a careful analysis of these constraints proved necessary in order to devise a design solution capable of preserving the site’s inherent qualities whilst also testing new sustainable design solutions.

After examination, we found that very few of the trees were worth keeping. This allowed us not only to partially clear the site for the new intervention, but also to salvage their timber and use it on the project: one small room has been lined with sycamore and we are developing a series of elements of furniture made from air-dried cherry, pear and walnut.

The exact position, extension and height of Covert House were dictated by its relationship to the nearby old house and its neighbours. Being constrained to a single-storey height inspired to build a semi-underground structure that sits well within its setting.

This solution might also serve as a socially sustainable model to subtly densify our residential areas and respond to the contemporary demand for more housing close to the city centre. Covert House follows some very strict rules in terms of not encroaching on the amenity of existing gardens by being for instance set back from its boundary fence on all sides. Seen from the neighbourhood around our site, Covert House is not overbearing and does not generate any overlooking.

Allowing for more well designed houses to be built in existing private backland sites may be a way for people to develop the assets they own while also releasing some of their equity. In a way, this is how all mews work: they encourage a pleasant neighbourhood feel and a sense of built-in security having neighbours near at hand.

DSDHA worked with Max Fordham on the environmental strategy to exceed Code 4. As a result the house is designed almost to Passivhouse standards and needs very little heating. This is due in part to the thermal mass built into the finished fabric, which responds extremely well to the thermal fluctuations typical of our climate. Moreover the structure is wrapped in a thick layer of insulation that guarantees minimal heat loss. High performance triple glazing allows for better heat retention and avoids the typical associated discomfort of using large expenses of glass. Moreover by having a whole house ventilation system we recycle heat that builds up in the kitchen and bathrooms to use it for both underfloor heating and hot water. The latter are also served by the solar thermal panels placed on the roof and by an air source heat pump that transfers heat from outside into the house. The ventilation system guarantees that a constant supply of fresh air is drawn from outside through the house, therefore maintaining a comfortable ambient temperature.

The self-compacting concrete that was chosen is made with 30% PFA (pulverised Fuel Ash). The use of plaster and paint on the walls has been avoided in favour of a simple fair-faced/exposed concrete finish that renders the house incredibly robust in terms of wear and tear.

In designing the house we have paid great attention to the sense of wellbeing created by connecting each space to the outdoors, though lightwells, clerestory glazing and full height windows. These also provide the lower floor rooms with access to verdant courtyards: outdoor microclimates in their own right that are shielded from wind and flooded with sunlight, therefore obviating any fears of living partially underground.

/21

×

Previous Next