Entrant:
Callum Dowie / Dowie Architects
Category:
9. Hybrid building award
Photographed by:
Sam Hartnett
Overview
Dowie Rose House
The Dowie Rose house is a 117sqm eco home neighbouring a rail line and cycleway in Avondale, West Auckland. The house was designed and built by Callum Dowie to investigate timber structural systems, prefabrication, and high-performance thermal envelopes.
A simple mono pitch form is used allowing the structural system to be repeated along the length. In addition to the glue laminated half portal frames and beams, the upper floor creates a timber diaphragm integral to the structural system. A concrete ground floor and precast concrete back wall complete the structure.
A hybrid construction has been used an insulated precast concrete wall reflects railway noise and provides thermal mass. A series of exposed Douglas Fir glulam half portals supporting the remainder of the house. SIPs roofing panels, and full height studs with counter battens allow twin layers of insulation, making this north facing abode cosy in winter. Window openings set high and low allow for passive cooling in summer. Multiple bespoke elements such as the timber staircase and kitchen, have been lovingly hand-crafted by the owners from upcycled materials.
The use of timber primary structure allowed for rapid assembly. Prefabricated primary framing took only 1 day to assemble onsite using a mixture of common and bespoke steel bracketry. Walls and windows are located between the primary frame structure and large glazed areas are possible.
The Level 2 floor structure is of European Spruce with two timber and steel flitch beams, 290mm deep, to support the stair well opening and forms a plywood diaphragm completing the structural elements of the building. The stair has been fabricated on site using glue laminated stringers with floor joist offcuts as treads.
The location of the house required a high mass ‘back’ wall to reflect the sound of passing trains, so a precast concrete wall was a good option, the structural and thermal performance offered by this solution allowed the use of a glulam primary frame which ‘leans’ on the concrete and gains bracing from the shear wall. A single bay of steel cross bracing is all that is required to brace the other longitudinal wall. The timber framed plywood clad floor provides bracing to complete the structure. The use of this system allowed windows and wall elements to be placed as desired without the requirement for bracing action by sheet material clad walls. More and larger windows were placed than is a typical NZ house.
The hybrid system allowed for a single morning of heavy craneage on the project (for the precast) all the timber frames could be lifted into place and bolted using simple scaffolding and ropes.
Custom-made steel plates, brackets and cleats were fabricated to allow simple assembly. Connection details were also made using proprietary steel brackets where possible. All glulam members were cut to size and drilled off site for accuracy and efficiency of installation. Structural brackets were painted red to highlight their locations.