Can Rooftop Community Gardens Be Retrofitted? 1

Monday, August 15th, 2016
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Some green roofs function as community gardens, and these spaces can be valuable not only for the building occupants (who cultivate the garden), but for building owners and developers, the wider community, and the environment.

Like all green roofs, however, their long-term success depends on how they are managed and maintained, and one of the unique aspects of the community garden model is the way in which maintenance is “outsourced” to the community.

I visited a green roof project at 38 Westbury Street in June and spoke to Sonia Bednar, who is a resident and the leader of the green roof project.

Rooftop vegetable gardening at 38 Westbury Street

The structure at 38 Westbury Street is a 1950s apartment building in St Kilda East with 23 apartments. For the first half-century of its life, the rooftop was a stark, white surface, which was only good as a place to dry laundry. In 2015, the building was retrofitted with a large (646 square metre) and accessible green roof. The retrofit makes this a different situation to a green roof at The Commons, which was crowned with a rooftop community garden from the start.

The green roof project at 38 Westbury Street was initiated and driven by the building’s residents. Bednar formed a committee, and they successfully applied for a state government grant. The grant was part of an initiative about the water cycle, and the primary purpose of the green roof is stormwater management. With funding for the design and installation secured, the committee engaged expert green roof installers and construction was soon underway.

Today, the green roof covers about three quarters of the total roof space. Much of the surface is planted with low maintenance, indigenous plants in a shallow substrate. This makes the roof an important addition to local biodiversity. Residents are also encouraged to use the roof, which includes crushed-rock pathways, stepping stones, decking, and two grassed lawns. It has become a much-loved communal space.

Although a relatively small portion of the roof is dedicated to it, one of the other uses of the green roof is food production. There are four planter boxes measuring two square metres apiece on the roof, and more are planned. Given that this was a retrofitted green roof, the planter boxes need to be carefully placed above structural walls to ensure that the roof can bare their weight.

The residents maintain their planter boxes and share what they have learned, through trial and error, with their neighbours. However, unlike The Commons (which has 46 beds – at least one for every apartment), the planter boxes are in short supply, so letters and emails were sent out to residents to find keen participants. The boxes are hand-watered as frequently as needed, which was almost every day in summer. The installer guided the residents through all of the future maintenance requirements and, like all good rooftop community gardens, there is a chalkboard and tool shed to encourage participation and communication.

The summer growing season (the only complete growing season to date) was very successful. The summer crop included some incredibly productive tomato plants and a lot of basil too. There were also strawberries, corn, chard, and lettuce. At the time of my visit, the planter boxes were being readied for the winter, for a crop that will include kale, garlic, rocket, broccolini, peas, and spring onions. Rosemary and lavender have been planted around the boxes to help attract bees and other pollinators, and warrigal greens provide some edibility elsewhere on the roof.

The planter boxes have been largely trouble-free so far. The only notable damage has been caused by possums, which climb the stairs to the roof, but many other potential pests such as slugs and snails don’t seem to make it this high. Even exposure to the elements has not been an issue here, possibly because the rest of the green roof provides the planter boxes with some protection from high temperatures and high winds.

The rooftop community garden at 38 Westbury Street is a great example of how these features can be successfully retrofitted on an apartment building, and how they can be integrated into a truly multi-purpose green roof.

The key lesson from this case study is the effectiveness of strong project ownership and teamwork, including an excellent understanding of what they wanted the roof to achieve. Under Sonia’s leadership, the residents have worked together not only to initiate and see the installation through, but to ensure that the roof has a very exciting long-term future.

But perhaps the most exciting aspect of this project is to think of how many other stark apartment building roofs are just waiting to come to life like this. It has paved (and decked) the way for the residents of those buildings to unite and make a rooftop community garden happen.

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  1. Roger Jones PEng FEC

    "… the primary purpose of the green roof is stormwater management." Really? I would have thought that it was cutting solar heat load and providing green space for residents.