Winner NZSEE Heritage Award
The Edwardian warehouse buildings at 2-12 Allen Street, (formerly known as Stock Exchange House) are in a special character area of Wellington. In light of the 2013 Seddon Earthquakes the owner wished to increase the strength of the structure from 45% NBS up to 70% NBS to ensure that existing and prospective tenants would want to occupy the space.
Numerous strengthening options were considered, but for the project to be economically viable the strengthening works had to be conducted whilst the building was tenanted. Another challenge was obtaining an encroachment licence from The Wellington City Council for extending the new concrete facade and footings into the footpath.
The strengthening solution was an external sprayed reinforced concrete ladder across the front of 2-6 Allen Street. The stiff concrete frame was a compatible strengthening element to complement the existing brick walls at the rear and its position at the front façade off set the torsion effects. The stiffness of the new front frame attracted load away from the rear wall so the brick was capable of sustaining the induced forces. A sprayed concrete shear wall was installed at the centre of the building at ground and first floor level against an existing unreinforced masonry wall. Otherwise strengthening incorporated additional steel straps at the floor levels to transfer load to the new structural elements.
The new concrete facade was formed and detailed to match the existing building which satisfied a peer review from a heritage architect and enabled a Resource Consent to be granted within the Courtenay Place Heritage Area.
To gain an encroachment licence we worked closely with the council to address their concerns, amending the design several times before all parties were satisfied. On the interior of the building the one vacant floor enabled the floors above and below to be largely strengthened without having to gain access and disturb established tenants, which included a bakery and a restaurant.
The construction work was carried out over 4 months with minimal interruption to the tenants. The character of the building, in respect to the Courtenay Place Heritage Area, has been maintained through successful collaboration between Wellington City Council, contractors and the design team.