James Alder takes a layered approach to Victorian extension

Who is the project for and what was the brief?

The brief was to create a new kitchen and dining room for a young couple, who wanted to extend and open up their existing flat to the lower levels of an established garden beyond. The result created an intricate, single storey, rear and side extension to the ground floor flat of a substantial, semi-detached, Victorian villa in Willesden Green, London.

Describe the original building and what you have done to it

The new kitchen and dining room was designed as a vaulted garden room for the home. Key to the project’s context was the retention and extension of a substantial brick party wall that had historically supported a symmetrical pair of pitched garden outbuildings and lavatories. These were already semi-demolished and had been heavily neglected in recent decades. Victorian glasshouses and ancillary garden buildings, built as appendages to the boundary walls of formal gardens, formed a particularly strong inspiration for both the formal language and the materiality of the project.

What was the planning context/situation?

Any demolition to the host property was purposefully kept to a minimum. In addition, the formal language and material sensitivity of the proposal led the planners to agree to a significant volume that extended far beyond the rear elevation of the existing property and rose to a significant height. This configuration also allowed for the retention of a rear bay window and door, characteristic of all the large Victorian villas in the area. A significant brickwork party wall was reused to support the reinterpretation of the outbuildings it replaced.

Explain the external treatment of the project?

The external façade is outwardly expressed in clay, with a continuous masonry plinth to all of the outwardly exposed elevations of the proposal. The tiling of the roof extends down, across the upper portions of the garden-facing elevations, and projects proud of the brickwork plinths, to create depth within the layered build-up of the façade components. Aluminium windows and bespoke trims to the reveals, all in a tone to match, ensure a strict continuity to the language of the façade. This approach ensures that the extension be read as a continuation of the material language of both the existing house, and the site’s former outbuildings.

Explain how the interiors have been designed?

No plasterboard was used within the extension, and all of the internal surfaces are purposefully left exposed and are tightly controlled. A horizontal internal datum, derived from the elevated floor level of the existing house, determines a reorientation of the internal blockwork, and defines the internal paint line. The exposed structural steel framing of the interior is the only element that breaks through this datum.

The internal volume of the extension rises and falls with the internal circulation requirements of the scheme, allowing the extension to manage the transition from the high level of the existing property’s ground floor to the lower level of the garden beyond.

Describe one challenge and how you overcame it?

Budgetary constraints demanded that an extreme rigour be applied to an informed use of cheap, standardised building components. This led to developing two contrasting skins that externally and internally formed linings to an ambitious structural steel framing configuration. This challenge helped to define the architectural language of the proposal, becoming a driving focus of much of the scheme.

What is your favourite detail/moment in the project?

The logic of the project is best characterised by the internal staircase, which is formed only from concrete lintels that span the space between an internal wall and a newly formed, stacked spine wall and bookshelf. It expresses a deliberate material honesty and is a celebration of the stark, layered construction employed throughout.

Which aspect would you do again next time, and what wouldn’t you?

The process furthered my interest in the layering, sliding and setting out of constructional logics, an interplay expressed in many aspects of the project. I will certainly take this area of exploration into subsequent work – though I would try to be less concerned with the minutiae of esoteric setting-out challenges and ensure  a more sustained focus on the expression of the whole.

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IN NUMBERS

Total contract cost £93,900
Area 28 m²
GIFA cost per m² £3,354