Green Roofs in the Domestic Environment

now available

This is a guidance note on Living Roofs in the garden, a leaflet published by Natural England in May 2006. It covers not just the why and the how but also what wildlife you can hope to attract to a living roof on a domestic or garden building. Download pdf [1.3MB]

This section provides more detailed information to accompany the leaflet. This is to help provide design guides and case studies of small scale green roofs.

English Nature became part of a new Government body called Natural England on 2 October 2006. The purpose of Natural England is to conserve and enhance the natural environment for its intrinsic value, the well-being and enjoyment of people and for the economic prosperity that it brings.

Livingroofs.org and Natural England are keen to publicise examples of green roofs in the garden. If you take the advice on this page and build a green roof we would really welcome pictures, examples of any innovative technique you may have used and any other information you think might be of interest to others. The number of domestic green roofs is still very small and your experience may be of real value to, and inspire, other people.

The information here is as comprehensive as we can make it. However, we do ask you to remember that we cannot possibly cover every situation and every contingency. What follows is therefore guidance rather than prescription. Most importantly, we strongly recommend that you get relevant professional advice regarding loadings and waterproofing.

We hope that this leaflet will encourage home owners to consider retrofitting green roofs on their sheds and on any flat roof space on other buildings in house or garden. Although the focus here is on sheds and other outbuildings, the same principles apply to flat roofs on extensions, balconies etc.

BEFORE YOU START:-

The first questions to ask are:

Is the waterproofing in good condition?

Can the roof taken the given load?

Then consider local wildlife:

What are the local and regional habitats that could be recreated on the roof and what species might benefit?
What soils and aggregates would be most appropriate and easily available locally? For example, limestone chippings from DIY shops would be good for limestone grassland.
Which plant species would be most likely to flourish in the conditions?
Although sedum species are recommended, do include appropriate flower-rich seed mixes or plug plants [www.wildflowers.co.uk is a good source].
AVOID seeding grasses! They will make their own way anyway, along with rosebay willowherb and other such aerial colonisers.
Add some moss from walls or normal roofs.
Include other elements such as dead wood, larger stones and nesting boxes to encourage invertebrates.
What butterfly food plants could be planted?
Be creative! Don’t worry if some of the plants don’t take or seem not to like the circumstances. Try others and add them instead.

PRINCIPLES:-

The essential components of a green roof are:

TIMBER FRAME to hold the green roof elements onto the roof. In some cases, extra timber supports may be needed to ensure that the building can take the load.

ROOT MEMBRANE – this could be a pond liner or 300micron damp-proof membrane.

FILTER SHEET – this stops fine material from leaving the roof. It is generally a sheet like the type placed under patios to keep weeds out. It holds the fine soils but allows water to pass through. It can be bought at DIY stores.

MOISTURE BLANKET – essentially a woolly fleece that holds water. These can be bought commercial and are referred to as geotextile membranes. Cheap alternatives are cardboard or even old blankets/towels will do.

SUBSTRATE – this is the medium in which the plants will grow and should consist of aggregate such as crushed concrete/brick, limestone chippings, gravels or clay pellets. This should be at the base to free drainage. Above it, you need another layer, consisting of sand or soil [preferably subsoil] or both.

PLANTS – the species selected will depend on the substrate and the substrate depth. They could be seeded or plug planted.

A Manifesto For Gardens, People And Nature

The Forum for Gardening with Wildlife in Mind, of which this organisation is a member, has produced a document entitled Let Our Gardens Live! A Manifesto For Gardens, People And Nature. The Forum (see * below) began in April 2005. It brings together a wide variety of organisations including Government agencies, horticultural and scientific bodies, nature conservation NGOs and commercial businesses, all with some interest in gardens and gardening, though from very different perspectives.

The manifesto was launched by the Minister for Biodiversity, Joan Ruddock MP, on 18th July 2007, at Roots and Shoots in the London Borough of Lambeth.

The manifesto has several aims. It will:

draw public attention to the importance of gardens for wildlife, for people and for the urban environment generally and to the threats that gardens currently face, from paving and development especially
set out an agreed agenda for future action
act as a rallying flag under which many different and disparate organisations can gather

At the time of the launch, some 31 organisations had signed the manifesto and in so doing pledged their support for what it seeks to achieve. However, it is hoped and expected that many more bodies will signal their support over the coming months and years.

The list can seen at

http://www.naturalengland.org.uk/campaigns/breathingplaces/manifesto.htm

The full text of the manifesto is at

www.naturalengland.org.uk/campaigns/breathingplaces/Docs/garden-manifesto.pdf

or can be downloaded in pdf format here.

* Purpose, objectives and Terms of Reference of the Forum for Gardening with Wildlife in Mind

Purpose

“To inspire people to manage gardens for their own enjoyment in ways which also benefit wildlife”

Objectives

To cultivate a responsible attitude to the natural environment on the part of gardeners and the garden industry
To gather evidence supporting the benefits, to people and biodiversity, of gardening with wildlife in mind
By relaying this evidence, to assist people to make well-informed choices about their gardening activities
To help link people and nature, through their gardens, thereby encouraging a wider and deeper appreciation of biodiversity and sustainability

Terms of reference

To provide opportunities for information exchange, facilitate mutual assistance, avoid duplication of effort and help develop partnerships among members.

SHED DESIGN

This diagram shows the basic principles for two types of garden shed

	Please note that the pitch shed will need a timber grid to hold material in

OUTHOUSE BRIGHTON

A simple green roof on an outside toilet in Brighton


The growing medium was chalk and sub soil and the idea was to create chalk grassland habitat for the Brighton and Hove Biodiversity Action Plan. Seed mix was a calcareous flower mix.

BICYCLE SHED, PETERBOROUGH

Eventually seeded with Sedum acre (Biting stonecrop) and Thymus serpyllum (Breckland or creeping thyme)

The bike shed in its unadorned state

A frame was constructed on top of the bicycle store.
It was not attached to the roof but merely placed on it

A root membrane was made using plastic compost sacks split open
and laid across the roof in between the timber borders

root membrane made of empty compost bags opened out

A moisture blanket made of six old bathroom towels laid between the timbers

moisture layer for green roof made from towels

Six battens were screwed between the timber up stands to hold the root
and moisture layers in place and to support the substrate

Expanded clay granules were placed in the compartments to a depth of 4 cm

clay granules / pellets used as substrate

with 3cm of soil [this was a blend of a 35kg top soil
and 25kg sand in bags bought from local garden centre].

soil and sand mix as top substrate layer

View a Domestic Green Roof Video courtesy of Groundwork Sheffield

View a Photo Gallery of Small Scale Green Roofs in Berlin

Cal's Green Roof shed in High Barnet.
Visit the Flickr website for photographs showing the construction

Mark Eccleston's green roof for his shed was made with the help of the Livingroofs domestic PDF guide that was funded by Natural England.

American Domestic Green Roof Case Study

An example of a domestic green roof in Raleigh, NC, USA can be found at these web addresses;

http://www.greenroofs.com/projects/pview.php?id=455

http://www.ncgreenbuilding.org/site/ncg/public/show_project.cfm?project_id=238