Housing New Zealand has embarked on an ambitious plan to increase residential density on its under-utilised suburban lots, in response to the growing New Zealand housing shortage problem. Inherent in the plan is the commitment to utilise prefabricated building construction with its attendant benefits of economy, speed of erection and safety.
The Otara, Manurewa and Papatoetoe apartment buildings in Auckland are amongst eight similar HNZ projects in train, all utilising full XLam Cross Laminated Timber structure. Three-storey walk-up developments, the modular design is expandable to suit site capacity. The Clayton Avenue site is typical, accommodating eight one-bedroom apartments which have replaced a single two-bedroom home built in the 1960s. Each apartment has a floor area of 55sqm, with a 9.7sqm balcony. Compact in size, they are intended to provide transitional accommodation for young people, run by the charity Lifewise, which battles homelessness.
From the ground floor slab up, all primary building structure is XLam CLT, utilising 3-layer preservative-treated Pinus Radiata panels. Each upper floor spans directly onto the transverse walls of the level below, providing an immediate working platform for the next level. The pitched roof panels span across the building to facilitate cantilevered eaves at the long edges. Wall panels are connected with engineered timber screws, and proprietary metal brackets and straps provide wall-to-floor anchors.
Balcony panels are set down to accommodate surface waterproofing and drainage, and cladding is fixed over a drained and ventilated cavity. Inter-tenancy walls incorporate plasterboard fire protection which also enhances acoustic separation.
Accurate off-site manufacture by XLam meant that on-site construction was very rapid. For the Otara apartments, the CLT site installation took only three weeks. It required one crane and a small workforce using mainly hand tools, minimising traffic and noise impacts on the residential neighbourhood.
Post construction evaluation
In line with its policy of continued research and improvement, XLam had comprehensive acoustic testing carried out on the completed Clayton Avenue apartments by consultants Norman Disney Young. Analysis of the results enabled a refinement of design details which will maintain acoustic performance while delivering cost savings for all future XLam-Housing NZ projects. Future projects will also embed other design efficiencies such as bluetooth, temperature, moisture, and movement monitoring devices.
“CLT is made from sustainable New Zealand timber. This is housing of the future and it is here, now. The new (Clayton Avenue) apartment building took less than six months to complete, which is around half the build time of a comparatively sized conventional building. That’s important when we’re trying to house people and families into warm and dry homes quickly. Housing New Zealand will increasingly look to use these building technologies as a way to deliver healthy, efficient homes more quickly to meet the growing demand for housing.”