small green roof project

Small-green-roof-project-growing media-copyright-waparchitects

The existing in-situ concrete slab was being fully refurbished to include insulation and a fully waterproof roofing layer and once completed, we decided it was a good location for a small green roof as it is overlooked by bedroom windows and is relatively easily accessible from a level area in the garden. The roof faces South West and is 2600mm long x 900mm wide.

At the outset, we wanted to source all our materials locally, but it soon became apparent that this would not be feasible in the small amounts we wanted.Therefore our project combines a mixture of proprietary green roof materials from specialist suppliers and locally sourced materials such as peat-free organic compost. It took a couple of weekends to build the green roof structure, apply the growing media and plant the roof up.

he roof is a test bed to try different types of planting. In October 2016 we decided to plant chives and sempervivums, both of which we already had in the garden, to give us some immediate interest and UK-sourced wildflower and grass seed for green roofs which we pre-mixed before applying.  Although we understood we may not get any wildflowers for 18 months, there were visible signs of small plants and grasses before Christmas. Logs cut from a fallen tree in the garden are used to encourage insects. By May 2017, the chives were flowering and the sempervivums thriving and a month later, some of the wildflowers and grasses had grown substantially. At this point we introduced several alpine plants, including erodium and armeria.  By July 2017, the chives were dying back, the sempervivums and alpines were still going strong and the wildflowers starting to flower.

We have seen robins, great tits, jays and goldfinches on the roof; one small issue has been jays pulling up the shallow-rooted sempervivums. Bumble bees are frequent visitors.  We're very happy with the results so far and will record the successes and failures over the coming months.

Please contact us if you would like a specification for a similar roof; we would be happy to talk it through with you.