If you’ve seen the visitor centre at Arbroath Abbey, you probably noticed that it has a living green roof. In other words, there are plants growing where you wouldn’t normally find them on a building.
Green roofing is a wonderful way to make the most of every single part of the building. Those plants not only pump out oxygen for us to breath, they help to insulate the building, prevent rainwater runoff and provide habitat for wee wild things.
This green roof was created by Bauder Ltd but you could easily do something similar on your garden shed, your front porch or even on a bird feeder.
Here’s how to make a simple, living green roof using the Enviromat sedum matting you can buy from Stewarts Turf in Edinburgh.
First make sure the building is strong enough
The Enviromat green roof build up we’re talking about is probably the least heavy way of building a green roof. But it is still quite weighty. The materials will weigh 40-45Kg per square metre. Then you need to factor in live loading. Live loading is temporary extra weight on the roof – for example snow. Or you. Walking on the roof to install the matting or check the plants.
You need to be confident that the roof – and the building as a whole, can support an extra 120Kg per square metre.
This green roofed summerhouse was designed and built by Edinburgh Based Caroline Grohmann of Secret Gardens Garden Design
Next the waterproofing
A green roof sits on top of the waterproof layer. It is not waterproofing. Make sure your roof is watertight BEFORE you add any of the green roof components.
If your roof is covered with a bitumen-based waterproofing – as many garden sheds are – protect it from root damage by covering it with a layer of thick polyethene.
Sedum plants – which are what grow in Enviromat – absolutely hate to have wet feet. Make sure your roof is well drained before you add your green roof layers. Look out for puddles that sit on the roof for ages after it’s stopped raining. They’re an indication that the drainage needs attention.
You will need an edging to stop your green roof layers drying out or being lifted up in high winds. Some roofs have a lovely upstand. On others, you will need to install a timber or a metal edge. Whichever materials you choose for your edging, don’t fix them on by nailing through the waterproofing. Make sure too that the edgings allow rainwater to drain away quickly and easily.
Green roof edgings are available online – just do a quick search on the internet to find your nearest stockist.
The green roof
Now the fun begins.
Hopefully you are confident that your roof is well drained, watertight, strong and has suitable edgings.
Your first job is to supplement the drainage by adding a layer of drainage matting. This is a really lightweight mat that literally just rolls out onto the roof. If your roof has a pitch of over 3 degrees you don’t need drainage matting. The slope on the roof is enough to make sure water doesn’t sit around for too long.
Next comes the sedum matting. Again, it’s simple to install. However, it is heavy. Lifting this stuff onto a roof is not a one person job. Makes sure you have help on hand.
Finally. Give everything a really good soaking with the hosepipe. Keep sprinkling until water runs off the roof. In hot dry weather, water daily for at least a week to help the plants settle in. In normal Scottish weather, just keep an eye to make sure the plants don’t dry out.
Here’s a video to show you how it’s done – there are some nice practical tips on here so watch it through to the end – it won’t take long.
If you have any questions about green roofing, Stewarts Turf are here to help. Call us on 0333 456 0019 for advice and costings.