A GUIDE TO ROOFTOP GARDENING

Gardening is no longer confined to the backyard. As cities become hotter and outdoor spaces dwindle, more people are reclaiming their rooftops. Across Brisbane, rooftop bars are popping up, hotels are turning their roofs into valuable assets and new apartment complexes now feature sky-high communal living areas. With a bit of clever thinking, you too can transform your rooftop into a lush outdoor living area.

Benefits of rooftop gardens

A rooftop garden has many advantages for your lifestyle and for the health of our cities. They add value to your property, clean the air and give you a chance to reconnect with nature – all with beautiful views in the background.

On a wider scale, rooftop gardens are one way to reduce the urban heat island effect that has led to rising average temperatures in built-up areas. With more than 65% of Australians living in our capital cities, just imagine the difference we could make to our cityscapes if more people put their rooftop to good use.

Here in Queensland, the Brisbane City Council has recognised the value of green roofs and recently added them as a key priority in the City Plan. Other benefits of a rooftop garden include:

·       More outdoor living space

·       A source of thermal insulation

·       More space to grow fresh food

·       Sound insulation for your property

·       Prolong the lifespan of your roof

·       Stormwater capturing

Types of rooftop gardens

Strong structures such as apartment complexes, larger homes and office buildings are generally able to support bigger gardens, but even the most humble rooftop can accommodate a few plants. The two main types of rooftop gardens are known as intensive and extensive. 

Intensive rooftop gardens

Outdoor living areas suitable for buildings with strong structures, intensive rooftop gardens are the type of garden that springs to mind when you imagine a lush rooftop space. They can support a soil depth of up to 1 m and heavier additions such as furniture, water features and shade structures. These types of rooftop gardens are also ideal for growing herbs and veggies, as fewer pests and insects make their way up that high.

image via: dspacestudio.com 

Extensive rooftop gardens

These gardens are a more modest option that are often referred to as green roofs or living roofs. They are easier to install and suitable for almost any rooftop. While they do add to the design of a home, they are most popular as a sustainable source of thermal and sound insulation. Because these gardens are lightweight, you can also consider planting them atop structures such as cubbyhouses, garages or garden sheds. Opt for plants with shallow roots such as succulents and grasses.

Chicago City Hall Green Roof image via: greenroofs.com

Cover your roof in plants to clean the air and naturally cool your building in summer. 

Design considerations

There are a number of challenges to consider when creating a rooftop garden, but the end result is always worth the effort. Choose plants that will handle the exposed conditions and remember safety considerations such as balustrades. More importantly, though, you need to think about how you can make the space liveable.  

Design

Consult an expert to assess how much weight your building can accommodate, as well as a landscape architect who specialises in rooftop gardens. They’ll be able to provide advice on how to get the most out of your space.

When designing a rooftop garden, consider the drainage and irrigation requirements of the space and incorporate obstacles such as solar panels, clotheslines or antennas into your plans. Depending on the scale of your design, council approval may be required. You’ll also need to ensure your roof’s waterproof membrane is intact and fully sealed before construction begins. 

Plants

Choose plants that can tolerate sunny and windy rooftop conditions. Use a high quality potting mix when planting and ensure the garden bed has adequate irrigation and regular fertiliser. When planting in containers, choose thick membrane planters and pots that will insulate plant roots.

Hardy plants such as succulents and agave respond well to exposed rooftop conditions.

Liveability

Wind and exposure to the sun are your biggest obstacles when designing a rooftop garden, which means that shade structures are essential if you want to make the space liveable year round. Shade options include fixed structures, retractable awnings and vergolas, which allow light flexibility. 

Tresarca Residence image via: assemblageSTUDIO

With an outdoor kitchen and a daybed, this is a luxurious rooftop living area.  Use curtains and textured structures to add shade that won't hinder your view. 

When it comes to purchasing outdoor furniture, invest wisely. Quality furniture may cost more initially, but will save you money in the long run. Furniture designed specifically to withstand outdoor elements should have UV-resistant paints and finishes, and waterproof fabrics and foam. When positioning furniture, place it next to a wall or structure that will act as a windbreaker.

By choosing pots and furniture that are on wheels, you’ll have the flexibility to rearrange the space to suit the best aspect of each season. You can add even more visual appeal with sculptures and water features. 

image via: denisebarretto.com.br

A well-designed rooftop garden features shade, wind-tolerant plants and quality outdoor furniture.  Choose sculptural plants and large pots for added visual appeal. 

Crunching the numbers

While rooftop gardens can be more expensive than those down on the ground, they can also be penny savers. They protect the waterproof membrane of your roof, which prolongs its lifespan by up to 20 years, and their shade and insulation saves on cooling costs in summer. With the added value an outdoor space brings to your home, rooftop gardens can become a sound investment.