Weathered Radial Timber Complements Aussie Garden

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The Australian Garden at the Royal Botanic Gardens Cranbourne features a number of exhibition gardens, sculptures and displays that showcase the beauty and diversity of Australian plants and their landscape.

The $5M Visitor Centre, located at the entrance to the Australian Garden, provides an information service, toilets, indoor/outdoor café and retail space. The weathered timbered building has been designed to give a tree top experience for visitors, offering glimpses of both the remnant bushland and the Australian Garden.

The complex was completed in two stages, the first in 2005 and the second in 2009. Architect, Kerstin Thompson, did not want to overwhelm the gardens. A pared back design, simple construction methods and the use of low key materials has allowed the gardens to stay the primary focus. By specifying recycled and sustainable timber products, Kerstin has maintained the site's environmental integrity and the Visitor Centre sits modestly, as an extension of its landscape.

Many key principles of sustainable design were employed and these environmental systems were kept obvious and simple enough that the public could replicate them at home.

Architect: Kerstin Thompson Architects

Engineer: Arup Australia

Builder: Behmer and Wright Pty Ltd.

Client: City of Cranbourne, Victoria

Careful consideration was given to levels and construction methods to minimise disruption to the site's ecology. Not just a solid mass on the landscape, the integrated design produces a prism - a series of interior spaces connected by timber decks and ramps. The monochromatic use of timber appears to make walls and decks as one, carrying the visitors along through the entrance.

The use of passive design principles, orientation and screening and glazing configurations maximised natural light, minimised solar gain and provided cross-flow ventilation. The Visitor Centre does not rely on elaborate mechanical systems for its high level of environmental performance. The use of slatted timber eaves and screens to control sunlight is delightfully simple. The architect proudly boasts the use of recycled local hardwood (Ironbark) for the doors and windows due to its low embodied energy and rustic character. The richness of timber meant the structure could be left unadorned and at one with its environs. Weathered grey cladding looks at home against the brilliant red Aussie dust.

The architect's challenge was to provide a way of apprehending the Australian landscape's diversity and richness. The buildings were to be a means of experiencing the topography and ecology of the site. Kerstin Thompson, the architect, said, "Our palette of materials consolidates this vision - weathered timber boards both allow the buildings to recede and provide a canvas against which to see the changing shape, colours and shade of the plants that are unique to an Australian sense of place."

The Visitors Centre is clad with the highly durable and economical Radial Timber Square Edge Weatherboard cladding system. Radial Timber ticked all the right boxes; sourced locally, sustainably harvested and low on wastage. The timber used for this project is class 2 durability Silvertop Ash, which is also a bushfire resistant timber. Screens were used as architectural highlights as well as for sun screening.

In keeping with the architect's vision the interiors enable maximum interface between inside and outside. High thermal mass and cross-flow ventilation keeps the interior spaces breathing and porous, responsive to climatic variation. Open and protected, the building can change with the seasons and provide a healthy environment for staff and visitors. The slatted timber ceilings create a warm and intimate ambience. Dappled light from the external pergolas filters gently through to the interior.

Acoustic performance

Timber performs strongly in the acoustic arena - whether the objective is to enhance sound or reduce sound. Its network of small interlocking wood cells converts sound energy into heat energy by frictional resistance within these cells and by vibrations within their sub-structure.

Because of this internal friction, wood has a stronger sound dampening capacity than most structural materials. While a concrete wall will also reflect sound, it does so in a much harsher way, resulting in stronger echoes. The natural acoustic properties of timber control this excessive echo, or reverberation, by reducing the transmission of sound vibrations. These properties of timber are why many public buildings, clad walls and ceilings are lined with acoustic timber panels or spaced timber battens.

Plywood and wood fibre acoustic products are used in theatres and auditoriums to provide low-frequency reverberation control. Timber acoustic paneling will often use holes or slots to increase the amount of sound absorption, essentially breaking up the energy of the soundwave. By breaking up the sound, the echoes are reduced.

A classic example of what can be achieved with timber acoustics is the Sydney Opera House. The interior walls are lined with Brush Box acoustic panels. Brush Box being chosen for its strong acoustic capabilities and durability. Ceilings in the Opera Houses' Concert Hall and Opera Theatre use white birch plywood panels with an acoustic plasterboard substrate. This world-class and iconic public building serves as an architectural and acoustic benchmark to this day.

To learn more about the acoustic performance of timber, see the following reports available for download:

Timbers used in this case study:

Structure

Framing: 

Ceiling battens of Silvertop Ash radial timber

Poles Beams: 

Laminated recycled Ironbark

Exterior

Decking: 
Windows: 

Stage 1 recycled Grey Ironbark

Stage 2 new & recycled Red Ironbark

External Cladding: 

Radial timber Radcon weatherboards in Silvertop Ash

Interior

Doors: 

Recycled Ironbark

Joinery Cabinetry: 

Armour Ply plywood

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