131 Queen Street rooftop by Bent Architecture

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The central hill, planted with succulents, has a wisteria-covered structure as the central focus.

The central hill, planted with succulents, has a wisteria-covered structure as the central focus. Image: Dianna Snape

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A series of elevated garden beds, seating and barbecue facilities have been incorporated on the rooftop.

A series of elevated garden beds, seating and barbecue facilities have been incorporated on the rooftop. Image: Dianna Snape

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The plant palette was chosen based on its low maintenance.

The plant palette was chosen based on its low maintenance. Image: Dianna Snape

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A rooftop of garden beds and gathering spaces provides a welcoming retreat from the hustle and bustle of Melbourne city life below.

In early 2009, the Growing Up competition, initiated by the Committee for Melbourne’s Future Focus Group, called for design submissions for the roof of one of three selected CBD buildings. The initiative was supported by various government and industry groups and aimed to demonstrate the diverse benefits of retro-fitting existing buildings with green roofs. It attracted thirty-two submissions from professionals and students.

The winning design, Head for the Hill by Bent Architecture, was officially opened on the rooftop of 131 Queen Street in July 2010. With a central landscaped mound surrounded by a series of garden beds and gathering spaces, the design displays a carefully chosen planting palette that allows for minimum maintenance. Traditional garden structures such as a folly, a gazebo and terracing have been incorporated. Rainwater has been collected from adjacent roofs to irrigate the edible gardens while permeable paving containing recycled glass and pebbles facilitates stormwater retention and drainage.

A series of elevated garden beds, seating and barbecue facilities have been incorporated on the rooftop. Image:  Dianna Snape

During the design process, amendments were made to the winning scheme to enable its construction. Originally the design included an accessible hill showcasing a mature tree. The low loading capacity of the existing roof prevented the installation of this tree or any large volume of soil. The hill is instead a low mound constructed of recycled, expanded polystyrene and planted with succulents accommodating a “tree sculpture” covered with wisteria. This departure from the concept results in the loss of greenery, shade and a vertical focal point.

The plant palette was chosen based on its low maintenance. Image:  Dianna Snape

Although it was a valuable learning process in retro-fitting a green roof for the young architecture firm, a sufficient understanding of structural constraints during the competition process is questionable. Although the achievability of the design was a jury principle and the loading capacities of the buildings were listed in the brief, some awarded designs included large trees and structures that could not be accommodated. Considering that loading limitations present one of the biggest challenges in designing and retro-fitting green roofs, this should be surprising.

Another part of the Growing Up brief has yet to be installed – the University of Melbourne’s research roof, part of a wider green roof study for the Australian Research Council (ARC). This could provide valuable data about the performance of green roofs under local conditions. Supported by knowledge sharing from the facility management of 131 Queen Street, the data will inform the local green roof industry, business community and building owners.

Through its enthusiastic work, the Growing Up team has generated invaluable publicity for the burgeoning green roof movement and attracted the interest of building owners by showcasing the design and construction online. Furthermore, the garden is a great asset for 131 Queen Street, enjoyed by a diverse group of tenants.

To maintain momentum, the partnership of public organizations, the construction industry, the design community and research institutions must continue to pursue the greening of Melbourne’s rooftops. The City of Melbourne’s Green Roof Forum, Canopy, is one example of a vessel for these conversations. The next step must be the establishment of green roof guidelines, policies and incentives for building owners to sustain the green roof movement.


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