Since I bought my shed, I've been itching to put a green roof on it, but I've always been put off by how difficult the task looks.
Since I bought my shed, I've been itching to put a green roof on it, but I’ve always been put off by how difficult the task looks. Luckily, a friend asked if she could do the job for me, for a book she's writing. So last weekend, she turned up with some wood, landscape fabric and pond liner, and transformed the dead space on my shed into a wildlife oasis.
High up above our cities, green roofs provide a refuge for endangered black redstarts, wild bees, butterflies and other insects, giving them a taste of what life was like before we built on the land. Green roofs on our sheds and bird tables don't provide such 'wild' habitats, but they do offer an additional source of pollen and nectar, as well as nesting opportunities.
There are other advantages too. London alone, is losing equivalent to two-and-a-half Hyde Parks of land each year. Not only is this reducing wildlife habitats, but it also puts pressure on sewage systems, as there is less land to absorb rainfall. This causes drains to back up, leading to flooding. If every building had a green roof - be it an office block or garden bin store - much of this water would be absorbed before it even hit the ground.
My shed has a tiny, steep roof, so we needed to make sure any soil that was added wouldn't just slide off. We also had to consider the extra weight the roof would place on the shed. First, the shed was reinforced with sturdy wooden posts, screwed to the inside walls. Then a piece of landscape fabric was laid on the roof, followed by the pond liner, which was placed over the fabric and glued to the sides. A piece of water-retentive matting was then placed on top. A frame was built and laid on the roof, then fixed to the wall behind the shed. We fixed horizontal batons inside the frame to keep the soil in place. Finally we added loam-based compost (made lighter by adding perlite and polystyrene chips), and planted it up with shade-tolerant wildflowers.
The day proved that building a green roof is a little more complicated than making a raised bed, as you need to consider drainage issues and the additional weight put on the shed. But it can be done without buying expensive kits. And, while the plants won't put on much growth before spring, I think the roof looks great. The shed has not buckled under the weight of rain-sodden compost, nor the trampling of pigeons. It won't be visited by black redstarts, but I can't wait to see the first bee, visiting a flower that would otherwise not have been there.
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