Despite what companies would have you believe, they don't install green roofs because they love biodiversity and the environment.
They love the tax incentives that they get from government and other local agencies!
In a recent talk by Nigel Dunnett of the Green Roof Centre he mentioned that in central Stuttgart, Germany (where modern green roofs originated) up to 60% of the roofs have some form of planned vegetation on them.
I checked this out on Google Earth and the picture below of a random section of the city shows it to be broadly true.
Image from Google Earth of Green Roofs in Central Stuttgart
The reason behind many of these tax incentives is that a green roof absorbs and delays water runoff from going into the main drainage network and overloading an already heavily burdened system. So a small investment by the authorities in green roofs delays a much larger investment in extending and improving the drainage system.
So why are homeowners installing green roofs on their sheds and garages in ever increasing numbers? Here are three good reasons that you might want to consider:
From a distance commercial green roofs can appear a bit of a messy brown smudge. However the sedum plants that are used for these roofs are quite attractive close up. In addition to the sedums you can introduce other species of green roof plants for year round interest. These plants include bulbs, ornamental grasses and meadow flowers. Also herbs can be grown in a roof type environment.
The hot, dry, exposed conditions of a green roof are good growing conditions for plants such as Thyme, chives, oregano and rosemary. If you do decide to use a roof as a herb garden you will want to include safe access as part of your design. One way to incorporate safe access to a shed roof was been demonstrated by Nigel Dunnet. He built his shed on a sloping site and this meant that the roof was easily accessible from the 'uphill' side of the shed without using any steps or ladders.
Lawns and flower beds in a typical suburban garden are very controlled spaces. A green roof can add a new type of space that is attractive to many new insects and birds that add interest to the rest of the outdoor space.
Sedum plants are a rich source of nectar and attract many types of bees. The dry plant environment attracts spiders and beetles who in turn catch flies. Birds are also attracted by all these insects. So in addition to the new plants that you have in your garden you have just made a welcome home for many species that have been struggling to find somewhere to live in our increasingly controlled urban habitat.
However you may be asking questions such as how often do I need to get up there to pull out weeds?
Some maintenance is required and each green roof is different, but in general only drought tolerant species will thrive in a roof environment. Some wind borne seeds may germinate but they will often not survive due to the dry and windy environment. So in general an abundance of weeds and unwanted plants is not a problem.
The occasional hardy specimen may survive though make allowance in your plan for safe access for the occasional spot of weeding. But as most green roofs have a wild untended look the odd weed will not look too out of place in the gap between maintenance visits.
The plants to watch out for are trees that grow root. They will start to grow taller and once established will get blown over due to lack of anchorage in the shallow soil. However an annual maintenance session is more than enough to sort out problems such as this.
However there are many other benefits that make installing a green roof a very interesting proposition. They will add beauty, variety and a great source of tasty herbs all within reach of your back door.
Keep in touch with our monthly newsletter
Shed Building Monthly