A glazed facade to match an original 1930s facade Although regarded as an early curtain wall, the original listed facade consisted of panellised steel window frames fixed at head and sill, with black 'Vitrolite' glass spandrels fixed to cast in-situ concrete upstand and downstand beams. The architect faced the problem of maintaining the original appearance while upgrading thermal performance by means of insulation, doubleglazing and thermal breaks.
The new bespoke facade by Scheldebouw is dimensionally identical to Williams' original and achieves the required performance standards.
The original steel sections have been matched in extruded aluminium. The original very slender intermediate mullions are sleeved with ss rod cores, post-tensioned to achieve the required strength.
Double-glazed units in extruded aluminium frames are fixed to a series of aluminium brackets which are in turn fixed back to the original concrete beams. At the head the frame is fixed to an aluminium sheet bracket, deep enough to give a consistent level against deviations in the line of the original beam. At sill level the frames are bolted to aluminium brackets anchored to the top of the concrete upstand beam.
Anodised aluminium sills face-fixed with ss dome-head screws match the original 'Birmabright' sills.The main window mullions are sealed with a zipper gasket to achieve a shape similar to the original sections.
The spandrel panels act as a rainscreen.They are framed with anodised aluminium extrusions and fixed through insulation to the concrete face with weathertight joints.
The vertical joints are covered with aluminium cover plates and dome-head screws.