VM Zinc (Umicore) Ltd - Zinc roof for house development on quarry edge

In the heart of suburban Kent, Munkenbeck and Marshall’s design of Quarry House in Sevenoaks is unusual in that the structure is built on the edge of a disused quarry. The design had to accommodate the unusual manmade topography while blending with homes nearby, so linking of quarry floor and ground level was achieved using a stepped construction. The innovative use of otherwise unusable land contributes much to the four storey building’s credentials. A long-term environmental problem has been turned into a visually impressive design, and enhanced by careful and extensive landscaping.
Several types of timber were considered while concepts were being drawn up, but a combination of larch, from an FSC accredited source for the structural elements and zinc for the roof was chosen to provide materials with similar natural ageing properties. The larch’s silver grey will blend with the gradual patination of the dramatic, curved zinc profile. Zinc was chosen for the practicality it offers with complex shaping and detailing and the low level of energy used in its manufacture. From ore, it uses the lowest energy level of the non-ferrous metals - less than half that of copper, and a quarter that of aluminium.
The existing house is being retained, and with other homes having an outlook onto the site, the new building’s overall roof height was restricted by planners. Even so, while giving the impression of being single storey viewed from ground level, the curved roof in fact incorporates two floors.
At 5100 sq ft, the design uses the environment to assist cooling of the building by drawing air over the cliff face. The roof structure, while providing a major breakthrough in contemporary design, also provides shading for natural cooling. An internal box gutter has been used to take rainwater away through the balcony areas via hoppers and 80mm rainwater pipes, also of zinc. Two shallow recess gutters were formed at the verges to prevent water penetrating end panel seams, with weathering slates soldered to 4 flue outlets on the roof. Fascias and soffits on the north and south elevation of the building were also clad in zinc.
Zinc’s attraction in designs of this nature stems in part from its recycling credentials, 90% of rolled zinc recovered from roofs and rainwater systems (around 100,000 tonnes each year) now being reclaimed in Western Europe, for use in galvanising as well as manufacture of brass and zinc oxide. Though not yet in widespread use as a roofing material in the UK, zinc’s sustainable credentials have already established it in common use for cladding.
All involved feel enthused by the project and feel they have contributed to a highly innovative, environmentally sensitive design solution which the client has singled out for particular praise. Use of terms such as unique are much abused but perhaps this home within its unusual landscape might lay more claim to the term than most.

Email: vmzinc.uk@umicore.com