Timber beats steel in a feat of 'Imagineering' by Futurebuild.
Outside of Gisborne near Woodend, is the site of the new Fletcher residence. The home, built in the style of the traditional
American barn, was entirely prefabricated off-site. The owner, Darren Fletcher, wanted an all timber structure but the original
engineer had designed the building in steel and had told Fletcher it could not be done economically in timber. Fletcher still
preferred a timber structure. After discussions with a number of engineers, the owner chose Tim Gibney & Associates to do
preliminary design and a cost comparison versus steel. The design and supply budget was prepared and it was significantly
cheaper than steel.
Tim Gibney and Associates are specialist consulting engineers marrying structural and geotechnical engineering. They do a wide
variety of engineering projects, including those in concrete and steel, and have set up Timber Imagineering, which specialises in
design and fabrication of timber buildings. The Woodend barn style dwelling is just the kind of project they are set up for.
The two-storey house is 12 metres wide by 24 metres long, a modular design with portals at 6 metre centres. The portals are Hyspan
Structural LVL sections and the floor joists and roof purlins are Hybeam Engineered I-Joists, both manufactured by futurebuild. The
entire structure was prefabricated in a warehouse. The timber portals were fabricated in sections and then transported to the site and
assembled on the slab and lifted by crane into position. The portals were rebated to allow for hidden steel gusset plates that occur
at the junctions where the timber changes directions. The base plates were fixed off to the cast in plate holding the timber to the
footing. Using an engineered designed footing system the portal frame size was minimised.
Robert Nestic of Timber Imagineering explains why the futurebuild engineered building products were chosen: "We used the
futurebuild LVL because of the guarantee of supply and material properties. LVL has high strength and reliability, suitable for these
types of structures and is available in long lengths and in a large range of sizes."
After prefabrication, the lower sections of the portals were sent for LOSP treatment, as the region is a termite prone area. The
timber building system allowed the owner to complete the construction with conventional carpentry techniques. This led to the
significant cost savings.
Timber construction was not only possible but was a cost advantage, resulting in a timber structure Fletcher had originally imagined.
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