Roof Gardens

Roof Garden Terrace for Seniors Living

July 1984, Victoria

A long, long time ago, I can still remember when (to pilfer a Don McLean line) roof gardens were relatively rare and primarily on top of underground car parking servicing office blocks (almost exclusively fronting St Kilda Road) or on podiums. They were proper gardens. My interest was so piqued by these that it led to my thesis in Landscape Architecture (this was back in 1984 - yes, I am that old), becoming my research project on this topic.

My thesis was to research nine established roof gardens in Melbourne. Each of these had its own particular issues; they were all relatively successful, and they used the essential ingredients in all roof gardens to establish vegetation on top of concrete, which is still the case today: effective waterproofing, free-draining soil, enough soil to support the long-term health of the plants, and, critically, a structure that is capable of supporting this load. All follow this same construction process.

There was plenty of optimism for the future of roof gardens back in the olden days. All large buildings could have vegetation on their roofs, which would green the city's appearance and mitigate the effects of the dreaded heat island. No surprise this hasn't happened, primarily due to the cost. To establish a well-vegetated environment on top of a suspended concrete structure requires a lot of structure, which becomes prohibitively expensive. This is all very logical; everybody loves the idea of roof gardens until the cost is mentioned, then they run for cover.

Courtyard terrace breakout space, but not a garden

One answer to building a full-fledged roof garden is to scatter plants in lightweight structures across a building. This gives the appearance of green without the investment, but, and it is a big but, it is prone to failure and is not for the long term. It looks good at first, but fades fast. This approach has become a go-to for cheaper builds - the roof garden you have when you aren't having a roof garden. Everything is in lightweight planters that can be moved around or replaced; there are no difficult-to-find leaks, and they are undersized, which leads plants to become root-bound and soil to dry out. The developer is happy, garden looks good on real estate photos - yet it is all temporary, akin to decorating with cushions in interior design. To my mind, these cannot be called roof gardens and have zero environmental benefit.

Native Australian wet sclerophyll forest garden was established in 2020 garden theme was changed by the developer in 2024 to a ‘Singaporean’ style garden.

MEMLA has undertaken both the ‘Elcheapo’ roof gardens and those that are the real deal. Their success depends on design, construction quality, and ongoing maintenance. A good roof garden should function like a garden on the ground. With regular maintenance, it should be trouble-free and long-lived, provide shade, protect from wind, offer seasonal interest, and be a place people enjoy. Trees and shrubs should grow to maturity, and planter boxes should be properly sized to support mature root development. The garden should have time to develop, with a regular maintenance regime as part of the body corporate service. It should be designed for the long haul, not simply dressed up to sell. Care also needs to be taken with soil type, as some lightweight mixes usually promote rapid plant growth but are not as good over the longer term (they dry out, and organic components decompose, leaving few nutrients). They primarily consist of composted material, sand, and scoria, with little true loam. This means they initially drain very well and support quick plant establishment, but they break down quickly. Soils with less composted material and more true loam are a little heavier, drain a little worse (which means you need good waterproofing), and growth isn’t quite as rapid; however, they hold up over the long haul, just like a garden on the ground.

Townhouse's and Tree Canopy Cover

AUTUMN 2025, VICTORIA

Due to Victoria’s population bursting at the seams, the Victorian state government introduced a new Townhouse and Low-Rise Code for Victoria.

In an attempt to streamline and ‘fast-track’ smaller developments, the Townhouse and Low-Rise Code for Victoria Clause 55, laid out in the 2023 Victorian Housing Statement, affects Townhouses, second dwellings on a lot and developments under four storeys in height.

Relating to Landscape Architecture Clause 55.02-7, encourages townhouse developers to meet the tree canopy cover objectives for their site early in the project. This approach aims to enhance shade coverage, improve the streetscape character, and reduce the heat island effect.

Local councils are increasingly treating canopy cover as a “pass or fail" metric, often scrutinising percentages down to the decimal point (transforming landscape architects into soft-core accountants). To avoid compliance issues, it’s crucial to incorporate canopy coverage and deep soil requirements into the design during the early spatial planning phase.

This process starts with a clear understanding of the specific percentage targets for your site. Once you’ve identified the percentage, the focus shifts to selecting the right tree species (Boroondara has a reasonable list) and locating them strategically. The final, and perhaps most critical, step is ensuring each tree has enough dedicated deep soil to reach maturity. By locking these requirements in early, the rest of the landscape and garden can be designed around these requirements, and your planning application won’t get Pollice Verso’d by your local bureaucrat.

Now that you’ve located the Canopy Cover and Deep Soil areas, the next step is to try not to compromise them.

This can be done by providing as many permeable surfaces around the site (granitic sand, permeable paving, decking, garden steppers, etc.) and locating all site services outside of Deep Soil areas. These site services include water tanks, AC units, stormwater infrastructure, bins, and storage sheds. However, if you’re going for more of a Mallee scrubland garden theme, perhaps the right plants may enjoy the fully ducted experience of being blasted by hot air humming out of a Mitsubishi INVERTER M Series.

What to do with Existing Trees?

Although existing trees within the site boundary can be included as part of the canopy cover percentage, we’ve had a few issues, especially with poor specimens. Removing existing trees with poor arboricultural or ecological value allows you to propose suitable replacement trees that align with the site’s long-term development, providing flexibility to the design of the external garden areas and improving the garden's ecological function (on a micro scale).

Removing an existing fruit tree of poor health with be better positioned new tree has allowed for a larger lawn and deck space.

After all this work, are we improving the streetscape character, shade coverage and reducing the heat island effect?

Hard to say. It certainly gives clarity to developers, town planners, and architects to allow for tree placement and landscape input early in projects. It also provides rigour for landscape architects to justify the location, size, and type of trees in a development.

This clause’s main outcome, for what we can ascertain, increases the likelihood that canopy trees in low-rise developments are well positioned, the choice of species is well considered and encourages more coordination between consultants. Gone are the days when we saw 50 Ficus hillii in a 500mm wide by 5m long planter boxes and 20m high Eucalyptus trees planted 1m away from a mains water meter. 

Considered implementation of Clause 55 Standard B2-7 tree canopy standards will ideally lead to long-term viability and mature life for urban trees in private developments, less hassle and maintenance for the eventual lot owners, and improved streetscape design outcomes for suburban Melbourne. 

Emmanuel College, St Paul's Campus

Stage 1-entry- 2001

When we first walked the grounds of St Paul’s campus, the landscape told a story of neglect and indifference. The site was defined by expanses of broken asphalt, compacted gravel, and paddock grass: humanity was missing. There was no sense of arrival; no shade, no plants, no paths, no landscape.

The recently appointed school principal, Chris Stock, was a breath of fresh air, bringing with him a clear and compelling vision for the future. Grounded in the values of Catholic Marianist education, the vision extended beyond buildings to the formation of the whole person, whole school and whole Landscape. It was a match made in heaven; we were a young firm full of ideas and enthusiasm, and he was the man in place to make it happen.

The first project to address was the woeful entry and parking situation. The corraling of parking allowed the school to separate vehicles from pedestrians and move them away from the front of the school pedestrian entry, improving safety while creating the opportunity to create a purposeful entry sequence. The new main pedestrian approach established clarity and order, guiding students and visitors through a structured landscape that signalled a journey to the school front door.

Hard surfaces were rationalised and refined. Edges were clearly defined. Circulation routes were legible. The previous ambiguous frontage became a formalised entry.

Planting played a critical role in this first stage. An avenue was introduced to define the entry corridor and provide long-term shade. Structured planting beds softened the built form and began to establish a campus identity grounded in permanence and care. The former neglected industrial landscape was now one of interest and beauty.

Importantly, Stage 1 was about setting direction. The relocation of parking and redefinition of the entry created the spatial foundation for future stages of development. It marked the beginning of a broader master plan vision for St Paul’s, one that would unfold over subsequent years. This first project signified more than new paving and planting. It represented a cultural shift. The landscape began to reflect the leadership and the values of the school community. The campus was no longer a collection of leftover spaces; it was becoming a coherent educational environment.

Shoreham Site Cut

Spring 2021, Shoreham

Arriving on site to meet clients during a wet spring in November 2021, we were greeted by a steep site cut akin to the trenches on the Western front in WWI.

We were engaged by the clients on the builder's recommendation, with building works already underway. Early in the project, the builder and clients discovered an obvious gap in scope. After undertaking the site cut, it became apparent that a 1.8m high solid clay wall—just 2m outside their rear terrace area—was not the ideal outcome everyone had envisaged.

The clients were understandably shocked and upset. They had expected a flat rear yard with views to the existing eucalyptus trees. We walked around the site, checking the extent of the cut, the proximity of existing trees, and access pinch points around the house.

Given the list of consultants they had already engaged for the lengthy town planning and building permit process, the clients were frustrated this issue hadn't been identified or communicated. We reassured them that a landscape solution existed (though we were admittedly a little shocked ourselves), through a design process that included 3D modeling, we could develop a landscape design that would suit their needs.

Design Process

The Design process was tangled but effective.

The Brief was to provide a flat lawn area outside the terrace, create bushland vistas from all main windows, and ensure safe access around the property so the clients could move confidently as they aged.

The landscape design took around 12 months to develop a solution that satisfied all parties. This process involved considering planning constraints and overlays (such as Bushfire, Significant Landscape, and Vegetation Protection), reviewing and integrating civil engineering plans, and re-engaging the project arborist to determine how close we could work to the existing eucalyptus trees while retaining them.

Initially, the clients wanted to remove all the clay and install concrete sleeper retaining walls to maximize the flat lawn area. We disagreed, advising that this would look too harsh and clash with the bushland setting they'd requested. However, the clients were persistent. To maintain the relationship and keep the peace we undertook this design exercise and engaged a structural engineer to design the wall.

After further meetings, site visits and walking the surrounding streets with the clients, we proposed the the softer approach of using locally sourced rocks with terracing to assist in retaining the land. These elements along with native planting would we insisted would harmonise with the existing Grassy Woodland (EVC 175) and significant remnant Eucalyptus pryoriana (Coast Manna Gums).

November 2022

After almost 12 months it was time to engage and Landscaper and start works on site.

From our earliest consultations with the builder, and client given the access challenges on site and the previous Geotechnical Engineers advice there was not going to be a ‘cheap fix’. The boreholes undertaken as part of the building permit, indicated the topsoil and subsoil was highly reactive silty clay soil which is a challenging medium that is notoriously difficult to excavate and costly to export off site.

The client prioritized a swift post-handover transition. After reviewing two comparable quotes, Centred Landscapes were selected as they were able to mobilise quickly breaking ground in early December 2022.

April 2023

The first priority was a privacy buffer along the northern boundary. We specified Acacia melanoxylon (Blackwood) for its rapid growth and deep green foliage. Highly adaptable to Shoreham’s fluctuating wet and dry conditions, these trees provided an instant, soft-textured screen against northern neighbours.

During the removal of 300m³ of soil, the delivery of oversized local boulders prompted a design change. By utilising these large rocks, we steepened the garden batters and eliminated a terrace level, resulting in a significantly larger, more fluid lawn area. Minimal root interference during the NW excavation allowed us to extend lawn even further, maximising the site’s usable footprint.

To manage stagnant surface water, we integrated sub-surface Ag drains into the existing civil infrastructure, ensuring the site remains traversable year-round. We also faced off against the local rabbit population. After an initial overnight grazing of the plant stock, we installed core-flute tree guards to ensure the plants species could reach maturity.

The result is a landscape that anchors the building to the site and blends structural boulders with the natural beauty of the surrounding bushland.

Thanks client’s Susy and Dan, Landscaper Paul and Builder Cam.