Contemporary Architecture in a West Hampstead Conservation Area

Scenario were approached by a couple who had purchased a run down office building tucked behind a large red brick apartment block in a West Hampstead Conservation Area. The property had an existing planning permission for use as a house as well as to extend down to provide a new basement level. Our proposal builds on this to add a partial storey above and rethink the external envelope in order to accommodate the needs of a family of four.

The design of the scheme has been developed with the intention of improving the contribution of the site to the West End Green Conservation Area through the provision of high quality residential accommodation that is sustainable and modern. 

Although it is not visible from the street, the existing single storey, L-shaped building is of poor quality in terms of both design and construction and is not considered to represent a heritage asset. In fact, it could be seen to actively detract from the prevailing character, appearance and significance of the Conservation Area. The site therefore presents an opportunity for enhancement of the built fabric in the area.  

The characteristic of the Conservation Area which is considered most significant is the brick faced Arts & Crafts (itself a subversive movement in its day) influenced Edwardian buildings, which comprise the street frontage of Crediton Hill. The proposal is located on a tight backland site set back 34m from this building line. Given its lack of prominence and distance from the public highway, the site is ideally suited for a contemporary house which is minimal, lightweight yet durable.

The alternative approach would be to replicate the predominant style of the immediate surroundings. These houses were constructed nearly 100 years ago and reproducing their style, detailing and method of construction would be unsuitable for a low slung backland development and result in a pastiche. We respect historic architecture but do not believe, especially given the advances in building methods and technology, that we should be producing it in the 21st Century.

Instead, the basis for the design is the interaction between the needs of the client and the constraints of the site. In particular, the mediation of light and the management of views both in and out of the property. A further major consideration was the level of access to the site and limited space in which to work, meaning that delivery, storage and removal of material would be extremely challenging. Therefore the design was conceived in such a way that off site construction could be maximised.

The proposed massing takes advantage of the substantial difference in level between the street and the cricket ground (circa 3.5m), which allows accommodation of the lower level in such a way that is completely hidden from Crediton Hill. 

The clients both spend a significant amount of time working from home. This meant that as well as living accommodation, the brief included workspace for each of them. This was provided in a partial mezzanine level sitting above the master bedroom. The tallest part of the volume containing this mezzanine was located along the Northern boundary which has an existing tall fence. This allowed the additional height to be incorporated with minimal visual impact on both of the adjacent properties.

Consequently, despite an increase in floor of nearly 200m2, the resulting structure above ground is only one storey plus the partial mezzanine.

The envelope is designed to optimise the environmental and visual performance of the spaces within. The existing building and granted basement extension include large areas of glazing, particularly facing East over the cricket field. These are retained in order to take advantage of all available natural light reaching the site.

Mindful of the potential for poor privacy levels, perceived additional overlooking of users of the sports field and excessive solar gain, the proposal is wrapped with a system of thoughtfully designed bespoke louvre panels. These selectively mediate the relationship between the internal spaces and the outside. The vertical fins are finished in light grey and set up a regular unifying rhythm across the facade.

In contrast to the walls, the roof is largely solid. This solidity is exploited to introduce expanses of green roof which aid the sustainability levels of the project. This treatment reduces the impact of overhead sun, acts to attenuate any rainfall and increases opportunities for biodiversity.

When designing, we always consider neighbouring properties and the wider context. The fact that all our design is carried out in a geolocated 3D environment brings immediate understanding of the effect on the proposal’s surroundings. We have carried out careful studies and analysis to ensure that loss of light, visibility and other impacts are kept to an acceptable level. As an example, the loss of sunlight in the garden of number 20 Crediton hill was assessed. The additional shade (blue) created by our proposal is minimal and this allows it to easily meet the BRE guidelines on overshadowing 

“BRE guidelines recommend that at least half of the garden or open space can receive at least two hours sunlight on March 21″

Given its siting right at the rear of the neighbouring gardens, the building does not create overbearing impacts or impinge on the outlook of the properties they serve. Views from these properties are altered but in general views themselves are not afforded protection and this is not a material planning consideration.

The existing building on site is almost fully glazed on the side facing the sports field, in combination with the granted basement, a large degree of overlooking has already been permitted by Camden. Our proposal should not raise significant overlooking concerns beyond what has already been allowed. 

The proposal uses modern materials and technologies in order to provide a highly sustainable development. External consultants were engaged to input their expertise, the design team went through several design iterations which resulted in the reduction of the amount of glazing, the increase of openable areas, as well as the introduction of the bespoke system of louvres which, among other things, regulate the solar gain.

The project also incorporates solar panels and an air source heat pump to reduce the electrical demand. The operable windows and skylights promote natural cross ventilation and the green roof previously mentioned promotes biodiversity. 

The design takes account of all relevant planning policy, which is set out in order to ensure that development is carried out in a considerate and sustainable manner. Working within these constraints with a detailed and expansive client brief has resulted in a building that is fit for purpose, optimises the use of the site and sits within the context without aping outmoded construction techniques and  historic styles.

Overall, the proposed development delivers an improved building to the area without removing anything that positively contributes to the locality. It represents a significant upgrade to the existing structure both aesthetically and in terms of sustainability. It also embodies what we believe to be the correct approach to development alongside historic fabric.