Space House (now Civil Aviation Authority House)

Space House, now Civil Aviation Authority House, is a speculative office development built between 1964 and 1968 by Richard Seifert & Partners, with George Marsh as partner-in-charge, for developer Harry Hyams.

The complex comprises two linked buildings: an eight-storey rectangular slab block at 45-59 Kingsway to the east, and a 17-storey cylindrical tower at 1 Kemble Street to the west. These are connected at first and second-floor level by an enclosed bridge. Both buildings use in-situ concrete construction combined with a structural outer grid of precast units, an approach that allowed rapid construction without scaffolding.

The Kingsway slab block follows an 'end core' plan, with circulation and services confined to the north and south ends, leaving the central two-thirds of each floor as uninterrupted office space. The tower contains a circular concrete core 67 feet in diameter, with six floor panels of 28 feet 6 inches span and pre-stressed beams extending to the external grid. Beneath the entire site lies an underground car park with curving entrance and exit ramps around the tower base; this formerly contained both public and private parking sections and a filling station, now removed.

The external treatment emphasizes the contrast between the two forms. The Kingsway block features a long rectangular profile that echoes surrounding Edwardian office buildings, while the tower's cylindrical form becomes fully visible only from Kemble Street or Wild Street. Both employ an external grid of tapered cruciform precast units, but handled very differently.

The slab presents flat-faced units clad in polished grey granite, with aluminium-framed glazing and dark spandrel panels set flush to the surface. Solid granite end-walls feature tall stair windows recalling an outsize Greek key pattern. At street level, large tapering concrete pilotis mark the circulation cores at each end. The south end was originally open but has been enclosed with aluminium and glass screens; the north foyer has been remodelled and enlarged with original shop units infilled for office space. The bridge connecting the two buildings mirrors the slab's treatment but has glazing recessed to form narrow galleries on each side.

The tower's concrete—a polished white Capstone aggregate resembling Portland stone—is left exposed. The precast units have sharply angled profiles with emphasised joints and glazing set well back, an arrangement designed both for visual drama and to shed rainwater and act as a brise-soleil. At ground level, the grid sits on massive Y-shaped pilotis, modified and enlarged versions of the units above. A raking zigzag canopy cantilevers from the western side where the filling station once stood. The Kemble Street foyer originally lay within the pilotis ring but has been modified and enlarged.

The interiors were never elaborate and have undergone substantial alteration. The Kingsway block's principal surviving feature is the south staircase, whose lower flights are a striking construction with floating concrete treads and white mosaic soffits. The north lobby has been remodelled, though original elements survive including the floating entrance canopy (since extended) and black marble wall revetments with a gilt inscription naming the original architects and builders.

The tower lobby has been heavily altered with the main staircase to the former first-floor showroom removed and all surfaces renewed, though the secondary stair with terazzo floor and white mosaic cladding survives behind.

The underground parking features sinuous entrance and exit ramps curving around the tower pilotis, supplemented by dramatic angular flying access stairs. Two air conditioning system features remain: an intake unit at the junction of Keeley Street and Wild Street, encased in a kidney-shaped sculptural feature clad in white mosaic, and an extractor unit further along Keeley Street, concealed beneath a polygonal concrete bench. The original landscaping scheme has been renewed.