After seven years of hard work, the redevelopment and restoration of the iconic Takapuna Grammar School main block and hall has been revealed. We talk to lead architect Natasha Cockerell and principal structural engineer Cathy Thomas about whatâs gone into this massive project.
Prendos and Respond Architects were commissioned to complete the design for the redevelopment of Takapuna Grammar Schoolâs main block and hall in August 2013 and construction began in April 2016. Natasha worked on the project from the beginning, and says it was a real balancing act between remediation, restoration and preservation.
âTakapuna Grammar is one of the oldest secondary schools on Aucklandâs North Shore. The main block, built in 1927, is a beautiful heritage building and a well-known, much-loved feature of the school and wider community. Unfortunately, because of structural and weathertightness issues, parts of it hadnât been used for more than two years. Weâve not only upgraded its structural and seismic standards, but delivered an upgraded, modern learning environment â all while preserving the buildingâs history.â
Recently unveiled to the public at the grand opening on 16 October, the schoolâs main block now houses an upgraded administration block on the ground floor and modernised teaching spaces on the top floor, complete with new heating, lighting, ventilation, sprinkler system and huge stacker doors to separate or open spaces as required. The external face of the building is even more impressive, as Prendos and Respond went to great lengths to restore and retain its striking heritage features.
Â
Â
âAt 17 metres tall, the historic main block was constructed entirely from 90-year-old bricks,â says Natasha. âThese were quite battered and damaged, so each brick was removed, individually cleaned and restored where possible, before being relaid. Where the bricks were too damaged, they were replaced with new matching âheritage redâ bricks.â
The cast iron rainwater hoppers that ran down the buildingâs exterior were original and had to be removed, repaired and resprayed. Because two additional hoppers were required, a mould was made of the originals so that exact replicas could be created. The buildingâs 130 original steel windows were also reused â each one carefully extracted and sent away to be refurbished, zinc sprayed, painted and double glazed before being reinstalled.
âWe added tinted double glazed glass to the windows,â says Natasha, âas the rooms previously got to 35 degrees during summer. The Quality Assurance process for each window required us to come to site and complete three separate staged inspections, so it was a painstaking process!â
Â
Â
One major heritage win is the buildingâs roof, where the entire parapet â made of lightweight precast concrete panels cast to match the original â was reinstalled to its original height (after being cut down in the 1980s in an attempt to reduce seismic risk).
âWith no plans to work from, we researched old photos of the original building. We could see the original parapet was taller, so weâve reinstated it to its previous height, which is more in line with the traditional architecture of the time.â
Heritage features aside, possibly the most complex part of the project was the buildingâs structural and seismic strengthening. This was a task given to Prendos structural engineer, Cathy Thomas, whose specialist knowledge of seismic strengthening made her perfect for the job.
âThe building was previously strengthened in 1993,â Cathy says. âToday we have a far greater understanding of earthquake strengthening and whatâs required, particularly when it comes to brick buildings. We looked at the overall bracing, reinforcement and connections. Because itâs a heritage building, we needed solutions that would last for the next 100 years â not just for a few decades.â
The team found that the buildingâs original concrete beams were rapidly deteriorating due to water ingress. Up to 120 beams went through a Quality Assurance remedial process, where they were remediated using a specifically developed process. Three engineering inspections were required for each beam.
âThe original beams had been made from concrete mixed using sand from Takapuna Beach,â says Cathy. âOver the years, their high salt content had caused them to degrade. Each beam was therefore reinforced and the building restrengthened so that they were no longer load bearing.â
Nearby steel beams were individually wirebrushed back and resprayed. New steel bracing beams were manoeuvred in through the buildingâs windows, with the biggest ones coming in through the roof. Each beam and junction was different, so each required a different steel plan.
âBecause Takapuna Grammar is close to the beach and is therefore exposed to salt air, the steel had to be adequately protected. When steel corrodes it can expand to six times its original thickness â essentially pushing out anything in its path. To avoid this we had to ensure the steel had a decent concrete cover to protect it.â
Floor by floor, the building was meticulously strengthened. Brickwork was repointed, new ceilings were installed, floors replaced, plywood bracing spread across the building, and timber framing installed between the steel beams.
Â
Â
âWe worked a section at a time,â explains Cathy, âremediating beams, installing lead cavity trays to catch water and reinforcing and reinstalling bricks. It was time consuming work!â
New bracing and connections were installed throughout the entire building, running vertically from the top through to the ground to transfer any seismic load to the foundations. New portals were also added diagonally to reinforce the building in that direction and better allow for earthquake movement. The buildingâs bricks, too, were connected and strengthened. âHelifixâ stainless steel ties were retrofitted by drilling them into the bricks to hold them together.
âIt been a constantly changing project and a real labour of love!â says Natasha. âWeâve collaborated with so many contractors and suppliers and had to work around all the buildingâs services â water, sprinkler systems, heating etc. The buildingâs age has thrown us a few curve balls too! During construction, for example, 100-year-old clay pipes were discovered under the floor. We had to stop work so we could design a pile- bridging solution to span over the pipes.
âThe job has challenged us in so many ways, but itâs something weâre all extremely proud of â a stunning heritage building that will deliver a really innovative learning environment for future generations.â