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Zinc Roof on Quarry House Development

Tuesday, August 07, 2007 by VM ZINC®

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, and linking of quarry floor and ground level having been achieved using a stepped construction. The innovative use of otherwise unusable land contributes much to the building's environmental credentials. What might have been a long-term environmental problem has been transformed by visionary architectural design and landscaping.

Several timbers were considered while concepts were being created, but a combination of larch from an FSC accredited source 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 provided for shaping and for its sustainability. Of the non-ferrous metals, it uses less than half that of copper and a quarter that of aluminium manufacturing from ore.

The existing house is being retained, and with other homes looking onto the site, the overall roof height was restricted by planners. Even so, while giving the impression of being of standard height when viewed from ground level, the curved roof in fact incorporates two floors. The thermally efficient material is ideally suited to formation in curved panel sections of this type.

At 5100ft², the design uses the environment to assist cooling of the building by drawing air over the rock face of the quarry. The roof structure provides shading for natural cooling, while an internal box gutter has been used to take rainwater away through the balcony areas via hoppers and 80mm zinc rainwater pipes. Two shallow recess gutters were formed at the verges to prevent water penetrating end-panel seams, with weathering slates soldered to four 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 100,000t each year) now being reclaimed in western Europe for use in galvanising and manufacture of brass and zinc oxide. Though not yet used as a roofing material to the same extent in the UK, zinc's sustainable credentials have already established it as a cladding material.

All involved feel enthused by the project and feel they have contributed to a highly innovative, environmentally sensitive design solution. Use of terms such as unique are much abused but perhaps this home within its unusual landscape might have more claim to the term than most.