Green roof in Wood Green

This is one I did last year that has been growing really well. The roof was on a new extension so the clients were able to design in extra big joists so we could support a good depth of soil on the green roof.

They managed to get a 5m extension so we had a good size to work with even with the skylights. It was waterproofed by the contractor ready for installation.

The team and myself laid out a protection fleece made from recycled material on the roof, then we added a drainage layer and put a filter fleece on the top to stop roots growing into it. Then we added the substrate, a special mixture of soil, lightweight aggregates, brick chippings etc, this is designed to keep the weight down, drain easily and also stop the plants growing too tall and need maintenance.

We put a gravel barrier round the edge of the roof and the skylights to assist drainage and add a firebreak. We also put extra gravel under the downpipe from the main roof of the house so the roof can absorb all the water from the roof rather than have it fill up the drains.

Moving materials is always a problem in London and we had to carry all the green roof substrate through the house and up on to the roof. Luckily Ecoalex has some good strong assistants so I didn’t have to do too much lifting. Once we had put out all the green roof substrate at varying depths we were ready to plant.

For this roof I had a mixture of mature plants and seeds. I included some Stipa tenuissima (the grassy stuff in the foreground) for the first time to see how it would grow and although it browns a bit in the dry periods it seems to be thriving. We also put in a few varieties of sedum to get some ground coverage including house leeks. Other plants included sea burnet and Sempervivum. I picked up all these plants at New Covent Garden Flower market in the morning a great place to pick up plants in London. But these are just to start the roof, the main coverage will develop over the next three years with all the green roof seeds we have planted I used a couple of mixes of native wildflowers including this one from Scotland that has 20 wildflowers and 3 grass species in the mix . Not all these will thrive initially but over time they should each find their own niche on the roof and grow nicely. Gary Grant likes to describe these seed mixes as an orchestra with all the instruments waiting for the conductor to call them in at the appropriate time in the green roof’s own symphony. Below are some pictures of the roof planted and how it has developed this year. More will be added over time.