The existing two storey structure is a steel frame encased in concrete with timber floors at the front and concrete beam and block at the rear. The first floor will be removed and two storeys will be added on top to provide nine flats in total and keep the ground level for commercial use.
The flats are either one or two bedrooms and include a terrace. The terraces are fully open with no balustrade or parapet going across at roof level – this creates vertical cuts providing a striking elevation and allows daylight within the internal private courtyards.
The new structure is a steel frame 350mm deep in parts but mostly 250mm deep with timber posijoists at first, second and roof levels.
Transfer beams will be provided as the upper level columns do not sit above the existing columns. The cantilevers will be achieved at each level with beams and back-props supported by new columns landing at the corner of the proposed glazing and by the existing columns.
The floor zone is 600mm deep and allows for services by having holes in the web of steel beams and by spanning the joists parallel to the proposed services. Timber joists 150mm deep will be provided with the main corridors to allow further services to be created in the ceiling void.
All the walls will be kept lightweight as well as the floor and its finishes. Brickslips for the cladding will be considered in order to reduce the added weight to the existing foundations.
The loads will increase considerably on the internal columns position, requiring strengthening on the columns and their foundations. Based upon further site investigations, the steel columns can be strengthened with new steel plates or channels welded to the existing. The foundations bearing capacity could be improved by mortar injection within the clay underneath the foundations.
Images by Barefoot Architects.