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Trend alert: Green roofs & living roofs

Save on heating and cooling costs, reduce your rainwater runoff and improve the air quality around your house – all while protecting the environment and fighting pollution. Green roofs and living roofs are not just a nice design touch, they're an environmentally friendly and energy-efficient building solution.

The Scandinavians have been on to this for years – well, centuries, actually. What’s basically a roof with plants growing on it is a common architectural feature all across Norway, for example, and not just in the rural areas, in inner-city urban developments as well. From lush lawn and golden grasses through to water-resilient plants and even small trees, a whole host of different planting styles is enlivening the building scene in Europe and beyond.

Rooftops can represent approximately 40 to 50 per cent of impervious surfaces in commercial and industrial areas, and up to 25 per cent in residential areas according to Auckland Council’s Auckland Design Manual in New Zealand. So there is a huge potential to add green spaces and manage stormwater issues. In Australia, too, green roofs offer a great opportunity to include additional, planted areas that look great while also helping with climate control, says Hashim Nasser from Refresh Renovations in Sydney.

“While living roofs have been primarily used for commercial buildings so far, they’re becoming more and more popular for residential homes,” says Hashim. “And while they are typically more expensive to install than a standard roof, they offer additional benefits such as climate control, lower energy bills for heating and cooling, and improved air quality.”

Terraced houses, which are commonplace in the UK and have started appearing increasingly in dense, urban areas around the globe, can really benefit from living roofs especially when considering an extension that would be overlooked by the upper levels of the homeowners and their neighbours. But even when you are renovating or building a freestanding dwelling in the country, using living roofs to blend the house into the environment can create a dramatic visual impact.

What’s the best way of building a living roof?

Things have moved on a bit from simply adding turf to the roof, and we now have access to quality materials and technologies that allow us to create living roofs with completely different designs. “The look and feel of your living roof can be fully personalised,” says Hashim. “The best roof for you will be the one that works for your lifestyle and budget, and also suits your house and environment.”

The main things to consider when you are building a green roof are weight and drainage. Living roofs comprise a vegetation layer and growing medium over a waterproof membrane. Needless to say that the roof has to be absolutely watertight and structurally sound. “Liquid membranes are more economical than Bitumen sheets, which again are more economical than torch-on sheet,” explains Hashim. “These would be applied on a primer layer.” Drainage cells and geo-fabric layers on top of the waterproofing membrane provide an excellent first line of defence against root penetration and deterioration due to potential localised ponding.

It’s important to work with a team of experienced experts, including architects, structural engineers, drainage engineers and builders, to ensure your living roof will flourish for years to come – and stay leak free. Detailed engineering calculations are necessary to determine the maximum weight the roof can take. During the installation phase, waterproofing specialists need to ensure the membranes are installed correctly and no air bubbles remain.

Legal requirements for living roofs vary across countries and regions, and it's important to check your council’s rules and regulations before you embark on a green roof project. Working with a renovation project management company can take the hassle out of creating a green roof, as a project manager can take care of all necessary permits for you and ensure that your roof is built to the highest standard and fully compliant will all local council rules and regulations. The specialists will also help you plan ahead to include proper drainage systems and soil retention methods.

Which plants should I use on my green roof?

Experts distinguish between intensive and extensive living roofs. Extensive living roofs have lightweight layers of free-draining media to support vegetation. They tend to be more suitable for retrofitting, as they are designed to be lightweight. However, they are generally not accessible except for maintenance.

Extensive living roofs require a special plant palette that is low growing and drought-resistant. “There are a lot of different plants that can work well and don’t have high water requirements,” says a Zones Landscaping Specialists in Tauranga, New Zealand. “You can create beautiful variations with grasses, flowers, succulents and many other types of plants.”

Intensive living roofs have a deep layer of soil to support a wider range of plants and garden features. Designed to be accessible green spaces, these types of roofs usually require additional engineering work and appropriate load-bearing structures. The Landscaping Specialists adds: “Where larger plants and shrubs are involved, the landscaping and gardening design options increase dramatically. For example, your roof could double as an edible garden where you can grow herbs, fruit and vegetables. This also provides a lovely habitat for many species. But bigger plants do have additional requirements, such as irrigation and a higher level of maintenance.”

Where regular roof access is expected, a proper staircase or ladder needs to be included in the design. Wall fencing and other approved fencing materials around the roof perimeters are also required, and it is worth considering a covered area in the roof design as a shelter to provide shelter from exposure to sun or rain.

No matter which type of living roof you opt for, it’s certain that it will add another level of ‘going green’ to your property.