A landmark restoration
In April 1904, Manchester’s rapidly-growing Co-operative Wholesale Society (CWS) opened their nine-storey, New Drapery Warehouse (aka ‘E Block’) in response to an acute shortage of storage and showroom space. Three years later, Hanover House – a continuation of E Block’s design concept and materials – provided the Society with the Mitchell Memorial Hall, dining and smoking rooms, committee rooms, and a suite of offices. Quality design, innovation, and a pride in the organisation’s impressive buildings, were priorities for the Society and all work (apart from tiling, roof steel, and decorative glass) was undertaken by CWS employees, exclusively.
Over a century later, working closely with architects, Sheppard Robson, BuroHappold Engineering’s multidisciplinary team has delivered a sympathetic refurbishment of Grade II listed Hanover House. Now a prestigious city-centre destination, it offers 8,310m2 of Grade A office accommodation and 2,905m2 of premier retail and leisure space. The project is spearheading the development of the wider NOMA-listed estate and attracting start-ups, established businesses, and dynamic new investors.
Refurbed and refreshed, the incomparable Hanover House, with its with unique features and substantial heritage appeal is set, once again, to become one of the city’s architectural jewels.
The conservation of a Grade II listed structure is a major challenge in itself. Especially in this case, as we had little historical information to go on, and the buildings are situated on a busy city-centre road network. Consequently, all construction work had to be detailed so that full access could be maintained for site delivery vehicles, pedestrians, and cars, without encroaching on the adjacent tram lines.
In 2015, E Block’s roof and mezzanine floor caught fire, however, proposals for reinstatement work were absorbed by the refurbishment programme.
At the heart of the redevelopment is a new lightweight atrium, spanning the courtyard between E Block and Hanover House to improve access from Hanover and Balloon Street, as well as to lend a complementary contemporary air to the design.
Incorporating a new mezzanine floor together with a mansard roof over the existing building required a careful assessment of the structural capacity of legacy floors installed over 100 years ago in this historically sensitive building. The two buildings predated any form of co-ordinated industry-standard defining superimposed loadings, so the structural assessment had to be based on the previous loading regime. The existing structure has been assessed, working to permissible stress methods and load compensation, to compare past use with likely future use.
The loading assessment took a qualitative approach (supported by targeted surveys) to investigating the building fabric in isolated locations, and to avoiding excessively intrusive opening-up works. This also minimised damage and kept our conservation intentions honest, while providing an opportunity to substantiate our design principles.
The new roof slab added a certain robustness to the original structure, laterally restraining the facade and perimeter columns.
In addition to the link bridge spanning the central atrium, four 21-person lifts rise to encourage circulation and connectivity between Hanover and E Block. The building can also count on passenger goods and fire-fighting lifts. Working within site constraints, the bridges were developed around a steel-frame to minimise weight, and constructed within the atrium. Steel beams form the primary bridge structure in support of the lightweight floor.
The roof is made from ETFE. Essentially, ETFE is a plastic polymer related to Teflon. It’s strong, with exceptional light transmission and structural properties, weighing in at around 1% the weight of glass. Transparent windows are created either by inflating two or more layers of foil to form cushions, or by tensioning it into a single-skin membrane.
Accordingly, the introduction of a new lightweight ETFE roof supported by new steel beams to span the previously open courtyard space was a valuable addition to the design.
The conservational approach to these two excellent buildings avoided demolition and any unnecessary site stripping. It also preserved a whole host of historical building features while creating a cost saving for the client.
A lot of the work relied on a site strip to expose the existing building fabric. We worked with the site team to incorporate temporary works items as part of the permanent design, again, saving money and delays to the construction programme.
A building services contractor wasn’t appointed until construction and refurbishment were already underway. This meant we had to be flexible, dealing efficiently with out-of-work sequencing and finding engineered solutions for late changes from the building services sub-contractor.
We pooled our knowledge of the building with the contractor’s temporary-works designer, helping with site logistics and finding effective solutions to working with listed buildings and a constrained city-centre site.
The vertical and horizontal building services worked within the primary structural bays to avoid the extensive structural strengthening works to the primary frame. Vertical services were accommodated by creating local floor openings to form dedicated service risers.
Similarly, the horizontal distribution was co-ordinated with the building services work to take advantage of existing openings in the building elevations.
Services and approach
When we integrate our specialist teams around an approach, the benefits to the client multiply