From loading bay to loft
The loading bay and courtyard was the last unit to be sold in ‘The Ziggurat’, a warehouse lofts scheme in London’s Kings Cross developed by London Buildings and designed to shell-and-core stage by Harper Mackay. There was little to recommend this gloomy undercroft space and roofed- over courtyard (400m2 in total); for a product designer in search of a one-bedroom flat with as much daylight as possible, purchasing Unit C was a brave act of faith. On top of the design challenge - transforming a service area into a contemporary home - there was a time constraint: the building had to be made watertight within 12 weeks to comply with the client’s funding arrangements.
Originally London Buildings had intended to put a new roof over the courtyard, but by confining living accommodation to the undercroft, Reading +West, architect for the refurbishment, was able to offer the developer the prospect of a landscaped courtyard as an alternative, thereby cutting the purchase price and construction costs - the dwelling would need no new foundations, walls or roof. Removal of an external roof had the added advantage of maximising daylight to the interior.
The building was conceived as a lightweight frame and transparent facade, contrasting dramatically with the massive concrete structure of the former warehouse. Prefabricated materials were specified to speed up on-site construction, and wet trades restricted to the rendered ‘bookends’ at either end of the glazed screen, the mauve end containing the entrance, the red end a bed deck and bathroom below.
The existing structure is used to support a new lightweight deck at the level of the old loading-bay dock, providing 7.5m-deep living quarters. The deck is insulated with 200mm of semi-rigid Rockwool batts and finished in birch-faced plyboard flooring panels. The glazed facade is supported by steel columns bolted on to the existing concrete floor on spreader plates and restrained at the soffit by ‘lollipop’ connections. The top of the W20 screen is secured by a continuous line of back-to-back channel sections, which also supports the upper band of butt-jointed glazing; the channels are supported by bolted outriggers from the columns. All screens are double-glazed and use low-E glass. The steelwork cantilevers 2m over the garden area to support an external iroko-clad deck. Landscaping plans for the courtyard are still being discussed. To achieve necessary U-values, the concrete canopy over the old loading bay and partly external back wall have been lined in thermal board. Elsewhere, concrete surfaces were repaired and painted. The entrance to Crinan Street has been transformed: an exposed steel channel punctuating the yellow-painted rendered blockwork infill.