University College Of London Hospitals: Centre For Ear, Nose, Throat and Dental Services
A unitised façade system, comprising brick-faced precast cladding, glazing and aluminium, was central to the design of University College of London Hospitals’ new Centre for Ear, Nose, Throat and Dental Services.
Set in a conservation area near Euston Station opposite a Grade II-listed Georgian terrace, the façade design faced rigorous scrutiny by planning authority Camden. The ingenious offsite solution devised by main contractor Mace, architect Pilbrow & Partners and precast specialist Techrete, not only met the design criteria, it ensured high quality standards and slashed months off the programme.
The Huntley Street façade features rows of wide bay windows which mimic the scale and layout of those on Gordon Mansions opposite, while the use of red brick evokes the largely brick-built surroundings and industrial heritage.
The modular approach required extensive pre-planning with Pilbrow modelling each of the 248 panels in BIM (The architects model was for an insitu brickwork façade, we developed the panelised approach).
The sections, which weigh up to 11 tonnes, use 160,000 handmade bricks supplied by Charnwood in Leicestershire, with the aluminium from curtain walling specialist Fleetwood and the units assembled in Techrete’s yard in Brigg outside Doncaster.
The complex bays on Huntley St include a perforated brick element, to increase solar shading, and triple-glazed windows. Each panel on levels one and two is around 5.5m wide by 4m tall, while slightly taller panels feature on the upper levels.
Spaces in the perforated areas reduced the contact area between the bricks, which increases the propensity for traditional mortar to crack when put under strain. An alternative solution was devised using ceramic spacers and a special adhesive to increase strength and flexibility. This required rigorous testing (defined by the Centre for Window and Cladding Technology’s technical notes TN 75 and TN 76) involving a 50kg bag being swung at the mock-up, which caused it to wobble significantly. Steel fixings had to be introduced into the backs of the bricks to increase rigidity.
The panels for the bays are supported on the reinforced concrete frame using billets which sit in pockets cut out of the edge of the concrete slab and restrained by torpedo brackets that screw into halfen channels cast into the concrete. These were designed in BIM and allow final millimetre adjustments to get the panels plumb vertical.
Other panels on the building include corner balcony units cast into the RC structure at the intersection of Huntley Street and Capper Street, while the largest elements are 9m-high curved chimney sections at the base of the Capper Street elevation, also inlaid with brick. The large size minimises the number of mastic movement joints in the brickwork.
Because of the irregular weighting of the bays, Techrete designed a bespoke lifting attachment to stop the panels tilting when craned into the air. This steel frame fits to the top and down one side of each panel to help keep it level and rigid when lifted from the back of the trailer.
Prior to installation, two test panels were assembled by Techrete and transported to the site for approval by project stakeholders, including hospital staff.
Up to five panels were installed each day, meaning the entire envelope could be completed and made watertight in just 13 weeks – a considerable saving on traditional build methods and with zero impact
on design and construction quality.