Wainuiomata High School | Lower Hutt

Wainuiomata High School redevelopment was a challenging yet rewarding project. The project was challenging due to the number of concurrent work packages and designs being progressed internally under a single coordinated design direction. This was complicated further with the detailed design being substantially progressed during the first covid lockdown while we grappled with these challenges through computer screens. The designs are varied responding to the Architectural, School and Ministry guidance and accommodating a combination of strengthening retained buildings and new construction. Mass Timber LVL timber portal frames features prominently in the new learning hubs, specialist building and support wing with structural steel construction in the Performance building, Gymnasium and various additions and strengthening. Geotechnical constraints necessitated designs to minimise weight and consideration of performance of adjoining existing buildings with varying existing foundations.

The school is located in an ancient valley that has been naturally infilled with approximately 30 metres of very soft alluvial and organic soils. Existing structures had visible signs that are consistent with foundation settlement. Geotechnical optioneering included deep foundations and ground improvement and shallow ground improvement options. To manage the geotechnical challenges most of the new concrete floors adopted shallow ground improvement consisting of lightweight aerated concrete and geogrids to load compensate for the new building. Some buildings such as those with timber floors were considered more tolerable to estimated movement and for extensions to existing concrete floors similar performance to the existing foundation was desirable. In these cases driven timber friction piles were adopted.

Photos: BCD Group & Stephenson & Turner

Disciplines involved:

Due to liquefaction and settlement concerns on the site the Geotechnical team proposed a modern solution of utilising aerated concrete. By placing the structure on the aerated concrete the weight of the building was no greater than the weight of the ground dug out avoiding initiating static settlement. This approach protects against liquefaction issues and limits post-construction relevelling required on this challenging site.
With the school located in the flooding zone the team provided site specific full flood hazard assessments and worked on improving secondary flow contours through the school to improve storm water drainage during extreme events. Additionally the team also provided full Three Waters design for the site.
Provided structural design from master planning through to construction for all new builds and strengthening works. The team initially provided both steel and timber designs to the client for consideration. The economic timber designs utilised spaced out portal frames to wide spans in conjunction with coldform steel purlins and was the clients design preference.
Provided the client and contractor with full 3D BIM modelling for the site for the works documented by BCD coordinated with the wider design team. BCD also modelled the services teams ducts and pipework across the site in the civil works modelling.