Biodiverse green roof in London

Last week I completed a ‘green’ green roof. Not only was it a green roof with plants increasing the amount of green space in central London but we also managed to use it to improve the energy efficiency of the house we were building it on.

The customers were really interested in using a small roof area they had to create a wild area of land to increase bio diversity. They are not far from Roots & shoots the environmental education centre and wanted to recreate some of the wildlife areas there. We planned out the roof to include different heights of soil, a wide range of native plants and areas of logs and brick dust to create habitats for invertebrates.

A week or two before the build I was on a CORE retrofit course learning about different types of roof insulation. This included a method where the insulation was placed above the roof’s waterproofing. This was perfect for this job as the roof already had excellent waterproofing and the plan was to lay the green roof on top of this. A quick call to the customer to ask them and they confirmed that the rooms below were cold so we added this to the project.

The project was planned over two days:

On day one we moved all the materials through the house, erected the scaffold tower and began laying the insulation:

There was quite a lot to move but it all went pretty smoothly.

green roof biodiversity
Green roof substrate

Day two started with us collecting some wood from the previous nights storm to create a log pile for invertebrates on the way to the site, oh and a full English for the guys helping with the work.

Installation of fleece and drainage layer
Installation of fleece and drainage layer

We made short work of installing the water retention


fleece, drainage layer and root barrier, all supplied by Optigreen.

Adding brick dust

Then we got to work laying out a pattern for the green roof, the original roof had been covered with gravel and we saved this to create a border and some patterns in the roof. We also added a couple of piles of brick dust to create some different habitats.  Once this was all laid out we filled the gaps with substrate of varying depths from 100 to 140mm deep, well within the assessed load bearing capacity of the roof.

The finished green roof

Finally we started planting. The Green roof consultancy gave me a list of plug plants, bulbs and seeds to create a roof of native species that will produce lots of interesting plants and flowers flourishing in the different environments created on the roof. We ordered them from Boningale Nurseries and all arrived looking healthy and ready to plant. I wasn’t sure how my workers would take to the plants as they largely do building work but this was

obviously much more interesting as they took the plug plants off me and planted them all in a good spread across the roof along with three clumps of bulbs. I was left to scatter the wildflower seeds an create our invertebrate wood pile.

London, green roof, sedum, biodiverse
Watering the green roof

The owners are delighted so far and we await the spring and new growth with bated breath.


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