Tag Archives: biodiversity

Marlow green roof update

Not all my green roofs are in London, you can see one of my early ones in Welwyn Garden City and this magnificent roof on a garage in Spring Gardens in Marlow

Shows edge detail and flowers
Lots of wildflowers growing here

The roof was installed early this year using Shire substrates and materials from Optigreen. I used expanded clay for the drainage layer and large cobbles to create a more natural looking border.

Wildflowers and sedum

The roof had loads of really nice seeds in it and was also planted with some sedums, aliums and stipa grasses and it has really blossomed tremendously.

the long edge of the roof

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.

Roof before adding the greenery
Roof cleaned and prepared 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.

The team lay out the substrate

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.

Planting, workers grass
Roof ready to be planted

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.

Low impact green roof in Marlow

Lots of green roofs going in recently and I need to spend more time documenting them. This one in Marlow on a garage was a new design that I am quite pleased with.

I have been working for a while to reduce further the plastics going into a green roof. I used to work with SUDS (Sustainable Urban Drainage Systems) a lot in the past and one thing I always noticed was the number of pipe manufacturers trying to shoehorn more plastic into natural drainage systems. Roofs obviously need to be waterproof so I can’t change that bit and we need something to protect it from sharp objects etc. Then comes the drainage layer which is lots of plastic sheets, this is important to hold a bit of moisture but also to makes sure it drains effectively. So drainage is important for weight but maybe we can make it of something else. For this roof we used aerated clay balls wrapped in a filter sheet that is held in place with some extra large cobbles. So the plastic is at a minimum.

The cobbles add a really nice touch to the edge of the roof and enhance the appearance considerably especially on a roof like this where there is no parapet. The soil is also held in place by the cobbles and I guess some of it may wash between them but not off the edge of the roof.

The roof has been planted with about 15 different plants, some sedum and ornamental, seeded with 30 different wildflowers and also bulbs planted to come up later in the year. I am monitoring progress and plan to pick up some crocus bulbs in autumn to plant.

Finished roof

If you like the look of this, drop me a line or give me a call 020 8133 0190 and I can see what we can do for you.