Last August we built a mini “roof garden” on one of our sheds. It faces west, towards the garden, but could also be positioned to face south or east.

First, we made sure that the roof was sound. The old roofing felt was in poor condition, but instead of replacing it with more roofing felt, we fixed sheets of corrugated, bitumen covered roofing on top. These are very durable and come in a variety of colours – we chose green. The roof should now last for many years, as long as the shed, if not longer. We bought our roofing material from Wickes, but it is also available from other DIY stores, such as B & Q.

Next, we built a wooden frame from offcuts of wood, to hold the “roof garden”. Ours is a rectangle measuring just 760mm by 500mm and about 70mm deep. It is fixed to the roof by a single piece of wood about 850mm long, along its lower edge. 70mm of  soil depth is not very much but it suits drought-tolerant plants; you could make it a bit deeper.

We added an offcut of lightweight permeable weed suppressing fabric to the box we’d built and then filled it with a mixture of garden soil and grit. We planted into this and finally spread a layer of fine gravel on top of the soil as a mulch. This looks good but will also stop weeds from germinating and conserve moisture. The box does not weigh very much, so it is easily supported by the shed roof.

As usual, the planting was the best bit. We chose Houseleeks (Sempervivum), Rock or Welsh Stonecrop (Sedum forsterianum) and Biting Stonecrop (Sedum acre). All are doing very well and are flowering as I write, surviving quite happily on Norfolk’s sporadic, low rainfall. Other species of Sedum, such as White Stonecrop (Sedum album), would do well too.

Why not give it a try?

If you want to do this on a grander scale, The Green Roof Centre website offers advice and case studies and Maddy Harland writes of her own experience of creating a Sedum roof on the Permaculture Magazine website.