90 Carrington Road

Entrant: 
RM Designs and Engco

Category: 
2. Residential design award for multi-unit residential buildings (up to 3 levels)

Kainga Ora, previously HNZ, had worked with the design and build team on the research and development, including the DFMA process , in respect of three level walk up apartments.

Carrington carried this philosophy of timber to the project.

Timber, and more specifically CLT, was opted for as the primary structural building material for this project due to it being seen as the best material when considering several key KPIs. These include but are not limited to; cost, build time, carbon footprint over the project lifecycle, structural performance, acoustic properties, and fire performance. CLT is a great building product when you consider that it is manufactured to high degree of accuracy, and incredibly quick to have a weather-tight building envelope. CLT is a lightweight option when comparing it to concrete saving cost on foundations and lateral bracing.

A significant portion of the CLT had to be enclosed for acoustic compliance. The staircases and the stairwell, and some common areas, were left exposed. This allows the residents to enjoy the natural warmth the timber provided when entering the premise. The staircase is aesthetically pleasing, firm under foot and robust.

Timber, or more specifically CLT, was a great material to use on this project based on its superior characteristics. It adds up financially when comparing against more traditional construction, whilst being a more environmentally friendly alternative. The CLT not only forms the structural system, it also completes the fire system when accounted for by the design (can often govern thickness). As the system is a pre-fabricated system, the whole thing can be assembled on site very quickly and had the roof on within 5 working days (ground to third storey roof). CLT is often preferred by the contractor as well, as it is often safer to assemble, fall protection is easier to manage, and contractors have very little time exposed to weather reducing down days and further increasing construction speed. CLT construction is often said to be 30% faster than most other alternative construction methodologies which means homes can be built faster alleviating New Zealand’s housing shortage.

CLT suited the project fire requirements. The timber structure was designed for a 60min charring. The protection is achieved due to the natural properties of the material in relation to act as fire retardant once charred after contact with fire. Especially for CLT walls were designed specifically for one sided charring.

Load bearing walls exposed to fire from both sides in one unit, were decided to be increased in size to provide natural resistance to fire. This saved additional plasterboard that would have been required to line the wall.

Each of these projects sort continuous improvement. This is particular applied to the façade depth and aesthetic which bore close scrutiny in this neighbour hood by planning authorities.

It is a good example that all DfMA processes, do not look the same.