A roof garden is any roof that is partially or completely covered with vegetation and supported by a mineral-based soil.
There are 2 types of roof gardens:
- Extensive roof gardens. These have a very thin soil profile of between 140mm – 200mm. The soils are specialised mineral based soils designed to be long lasting with minimal degradation over time. The plants range from ground covers up to small shrubs and all require irrigation for establishment and sustaining over dry periods. Often the supporting structure is of lightweight construction, eg 25mm plywood. The extensive green roofs are usually non-trafficable and only accessed for maintenance visits.
- Intensive roof gardens. These have a deeper soil profile of 200mm up to 1-2m depending on structural load bearing capabilities and what is to be accommodated in the plant pallet. These look like parks on the roof and are made out of concrete bases and are trafficable hence require fall protection as part of the design.
Both roof garden types can be sloping up to 45 degree and made up of all shapes and sizes.
All roof gardens require a waterproof membrane that is designed to be used under roof gardens. SRS Group do not supply waterproof membranes, but your architect will be able to guide you on the best solution for their design.
Globally roof gardens have become popular in urban areas, helping to soften our towns and cities and mitigate the effect of storm-water runoff into marine and waterway ecologies. Many cities require large expensive civil infrastructure to handle large volumes of rain water run-off from built up areas. As cities grow rapidly the growth of infrastructure lags behind causing many problems for the city.
Benefits of Roof Gardens
Roof gardens come in all sorts of shapes and sizes. Whether you are looking to create a green space that delivers environmental benefits or you are looking to create a space where more traditional gardening can take place, there is a wide range of benefits to installing a roof garden.
A roof garden helps with the management of stormwater runoff. During a rain event water immediately runs off a hard surfaced roof into a drain system that flows into a city’s stormwater catchment and distribution system. As cities grow the stormwater system will quickly get to a point of overload during a rain event or downpour. When a roof garden is installed the rain water is absorbed into the soil layer until the soil becomes saturated then the water is released down through the soil profile to the drain system. This retardation of water run off reduces the immediate demand of a rain event’s run onto a cities stormwater system. Also as the rain filters down through the soil profile many of the pollutants or smog components are removed from the rainwater.
Expanding outdoor living space within the same property boundaries
We have many examples of where the addition of a roof garden allowed occupants to recreate on the roof making more usable areas for the same property. With a wide range of activities enabled with roof gardens the add on effect is a community evolves with the occupants through contact on the roof. This adds value to the building and generates a return on the initial costs of installing the green roof.
Most roofs are exposed to extremes caused by the weather. Sun, wind, rain and snow all have an impact on your roof, causing the roof layers to shrink and expand which takes its toll on the lifespan of the typical roof. Adding a rooftop garden can help to significantly extend the lifespan of your roof components, helping to save costs in the long term.
This is done in 2 ways:
1. Direct energy savings to the building itself
There are 3 layers to a roof garden:
1.) Drain layer at the base
2.) Soil layer above that
3.) Foliage layer on top.
Each of these 3 layers has a thermal mass and an air content, creating an insulation blanket on top of the building. This enables the roof garden to keep hot air out during hot sunny days and thus reducing the air-conditioning demand.
2. Reducing the effect of the heat island effect.
Caused by the use of materials such as concrete, steel, glass and asphalt these all reflect heat in urban areas elevating the overall immediate area’s temperature during hot seasons.
A roof garden eases the heat burden, helping to keep buildings cooler during the warmer months. Studies show with only an increase of 10% of rooftop areas converted to roof garden has a dramatic effect on the heat island effect.
SRS Group – helping bringing your roof garden dream to fruition
If you are thinking about installing a green roof, talk to the team here at SRS Group. We have experts who have been working here in New Zealand and in Australia, delivering green wall solutions to a variety of commercial and residential buildings.
Our enthusiasm for living foliage structures and roof garden spaces is two-pronged – it offers an edgy, on-trend yet soft design aesthetic, along with proven environmental benefits for both people and Mother Nature.
We combine a passion for creating impactful spaces through the use of foliage, with an unwavering commitment to sustainability.
Installing your roof garden
There are many benefits to rooftop garden spaces, however, it’s important that the installation of a roof garden is undertaken by professionals.
One pivotal component of a rooftop garden installation is the waterproof membrane that sets the foundation. SRS Group do not supply waterproof membranes, but your architect will be able to guide you on the best supplier for their roof garden design and we will work in conjunction with a supplier once they have been appointed.
Using a thin soil profile of an extensive roof garden has advantages in reducing weight but it needs to be a mineral based soil mixture with minimal organic content. This ensures longevity but requires regular feeding and irrigation during establishment and hot dry periods.
Our team botanist will then work with you to ensure the plants selected – and how they are positioned – will be ecologically sustainable and matched to the green roof’s growing conditions.
Talk to us today
Talk to us today about a roof garden solution for your building.