Hoete Whanau Papakainga

Entrant: 
Anthony Hoete / Anthony Hoete

Category: 
4. Mid-rise building design award

Photographed by: 
Manuel Rodríguez Fernández (Nivelarte)

Project overview

1. Our five-storey whanau project utilises Cross-Laminated-Timber (CLT) as its means of construction because it provides:

Innovative residential long-term security of tenure through a Build-To-Rent papakainga development

Innovative interior décor treatment where the CLT superstructure is expressed in the ceiling and wall finishes, eschewing the ‘fakeness’ of plasterboard, yielding greater affordability

Innovative carbon sequestering with smallest carbon footprint when compared to metal or RC frames

Innovative CLT construction programme requiring ten days, one 55-tonne mobile crane, and five articulated lorries, minimising traffic, and neighbourhood noise disturbance

Innovative offsite digital fabrication with 2mm CNC cutting tolerances facilitating pre-ordering of Schueco double-glazed windows before superstructure erected

Innovative and distinctive 'leaning mansard' form

Innovative lightweight structure reduces loads on RC substructure and ground disturbance to neighbouring three-storey boundary property

Innovative CLT superstructure costs allow for more expensive RC substructure – the waterproofed and tanked naturally-lit subterranean living spaces dug to provide for additional living accommodation

2. Various engineering challenges were overcome.

The structural challenge of the leaning mansard was met by the diaphragm / shear action of CLT walls. This allowed the upper floors of the top two apartments to lean out towards the neighbouring garden, intensifying the living relationships with nature, the trees, the birds, and the bees.

The acoustic performance of CLT housing can be a serious challenge. Horizontal airborne sound transmission was however attended to by dividing the inter-tenancy party wall into two vertical 120mm thk CLT walls separated by a 200mm wide cavity (then partially filled with 70mm thk 40dBA Rockwall acoustic slabs affixed to the inner surfaces). Vertical impact sound was also diffused using high load bearing (10,000kg/m2) dense Regupol 6010SH rubber at the junctions of the (230mm thk) CLT floors and the (120mm thk) CLT walls.

The fire engineering challenge was resolved through calculating the wall thickness required to achieve 60min fire integrity to untreated CLT. For our project, this requires a 90mm post-charring thickness. However, three intumescent coatings were also applied to delay the onset of ignition by a further 22 minutes as extra precaution.

3. The use of CLT was expressed to the exterior through the iconic leaning mansard form and expressed to the interior via the visual grade exposed timber aesthetic.

By leaning the upper two floors out towards the neighbouring park, no internal floor space is lost as with a standard mansard seen elsewhere along this terraced street. Like the mansards of Paris, roof space becomes 100% utilisable, rather than with the tin-hat void common to many NZ residential roof spaces.

4. Visual grade CLT made the project more affordable as no window linings, architraves or skirtings were required. Nor any plastering or painting. This meant the housing was more affordable without reducing floor area with a natural, more honest material expression to the interior spaces.

5. The superstructure is pinus radiata CLT.

6. The project was design-led by a Maori architect who functioned as developer and contractor, offering an exemplar for future NZ housing.