May 2004 Jacklyn Johnston & John Newton

Building GreenA guide to using plants on roofs, walls and pavements

Greater London AuthorityMay 2004

Published byGreater London AuthorityCity HallThe Queens WalkLondon SE1 2AAwww.london.gov.ukenquiries 020 7983 4000minicom 020 7983 4458

ISBN 1 85261 637 7

This document is printed on 75 per cent recycled paper, 25 per cent from sustainable forest management

Originally published by the London Ecology Unit, 1993. TheLondon Ecology Unit was abolished in 2000, and absorbed intothe Greater London Authority. The text has been reprinted here,but not revised. Some images have been replaced.

Jacklyn Johnston is a principal ecologist with the London Ecology Unitresponsible for project development. Previously, she has been communityliaison ecologist for the Greater London Council, worked for a firm ofarchitects and planning consultants, and been a partner in an ecologicalconsultancy. She specialises in the community aspects of urban ecology,and gives advice on establishing nature parks and ecology centres andintegrating ecology into the built environment. She has written manypopular articles about nature in cities, including a book Nature Areas forCity People, published by the London Ecology Unit.

John Newton has worked on environmental issues for over 20 years. Hehas managed nature reserves in both Norfolk and Suffolk, been DeputyDirector of London Wildlife Trust, and Environmental Manager for theproperty company Rosehaugh. He now runs his own consultancyspecialising in ecological and environmental research and assessment.

copyright

Building Green A guide to using plants on roofs, walls and pavements 1

PREFACE

INTRODUCTION 7

1 THE NATURAL LANDSCAPE OF THE CITY 9Opportunities for greening the ecological city

2 BENEFITS OF GREENER CITIES 10Cleaner airImproved climateSlowing down stormwater runoff and absorbing pollutantsProvision of wildlife habitatsGood investmentsProtection of building surfaces

3 TREES AND BUILDINGS 13Amenity valueEnergy conservation and wind-loadingImprovement of climateWildlife benefitsTree sizeSuccessful plantingRetaining existing treesTree management

4 COURTYARDS 23Forgotten potentialMicroclimate Light, wind, moisture, temperatureSuitable plants

5 BALCONY GARDENS 27Linking indoors and outdoorsVisual benefitsOpportunitiesChoosing suitable plantsManagement

6 GREEN WALLS 31BenefitsLiving conditionsPlanting techniquesChoosing suitable plantsManagementAlternative green walls

contents

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7 BUILDING FOR BIRDS AND BATS 41NestboxesAdapting the buildingUsing plantsSome urban birds and their nesting requirements

8 GREEN ROOFS 45Visual appeal Environmental benefitsLiving conditionsIntensive and extensiveEarth shelteringTechnical considerationsAppropriate substratesChoosing suitable plantsPlanting methodsFauna and floraManagementCosts

9 GREEN BUILDINGS: A VITAL PART OF SUSTAINABLE CITIES 75Broader green schemesPrinciples of sustainable developmentBlock 103, BerlinTorsted West, Denmark

CONCLUSION 81

TECHNICAL INFORMATION 82Tables of Plants Suitable for Different Situations

Trees for urban areasPlants for containers on balconies and terracesClimbers, ramblers and fruits for wallsPlants for extensive green roofs

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SUPPLIERS OF EQUIPMENT 95Tree guards and grillesPlantersGreen walls and fencingRoof systemsPavingBird and bat boxesTreesClimbing plantsAlpine/rockery plantsWildflowers and herbsSoil conditioners and substrates

USEFUL ORGANISATIONS 99

REFERENCES 103Please note that numerals in the text refer to numbered references listed in this section

FURTHER READING 107

INDEX 112

PICTURE ACKNOWLEDGEMENTS 120

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Southwark Crown Court

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This book is a significant new departure for the London Ecology Unit. Forsome years the Unit has been providing an advisory service on ecologyand nature conservation in the urban environment. Much of our work hasbeen concerned with protecting important natural habitats, which areincreasingly under pressure for development. Local groups regularlycampaign to save particular wild areas simply because they are the onlyplaces in the neighbourhood where anything resembling the natural worldcan still be seen, especially in the densely built-up areas of inner cities.We frequently argue for the protection of such places, many of whichhave developed entirely by chance, not by design.

I am constantly made aware that if we were to design cities to includenature the picture could be very different. The Ecology Unit has alreadybeen successful in creating new habitats, where people can experiencewildlife in their local neighbourhood, and this has led us to appreciate theconsiderable opportunities for creation of new habitats presented by thebuilt environment itself. It is for this reason, therefore, that the EcologyUnit has produced Building Green in an attempt to encourage morewidespread use of plant life within the built environment, whether in newdevelopments, or within the existing fabric of the city.

In embarking on this project we were fortunate to establish a partnershipwith John Newton whilst he worked with Rosehaugh plc, and he was ableto bring his considerable experience from the viewpoint of major newdevelopments. We have also capitalised on our links with the EuropeanAcademy for the Urban Environment in Berlin, a city where the concept ofgreen roofs is now well established, as well as drawing directly onexperience from Toronto and several Dutch cities.

I hope that this book will provide a useful starting point and a source ofideas on the greening of the urban environment, not only in our capitalcity but in towns and cities everywhere.

Dr D A GOODE BSc FLSDIRECTOR, LONDON ECOLOGY UNIT

preface

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The Toronto skylinefrom a roof-top garden

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What sort of image does the word city conjure up for you? Tomost people it suggests a hard, abrasive environment. Isolatedpatches of green space offer welcome relief, but these usuallyturn out to be sporadic refuges. Cities need not be like that

Creating more enjoyable cities by greening them is a realistic objective. Itis the concern of many politicians, planners, and environmentalists:greener cities would bring immeasurable benefits to the people who liveand work in them all over the world.

But however desirable, greening the city is a complex undertaking. Ittouches upon transport systems, water management, air pollution, energyconservation, the recycling of waste, nature conservation and many otherinterconnected issues. These issues have been the subject of numerousreports, papers and books, notably the European Commissions GreenPaper on the Urban Environment and Friends of the Earths Revivingthe City. They are crucial matters, requiring urgent action, but they arenot the subject of this book.

Building Green concentrates on one key aspect of the greening process:the use of plants on and around urban buildings. It goes without sayingthat this can only be part of any overall greening strategy. However,green buildings and greenspaces together define an integrated approachto plant life in cities that is central to any green programme. At the end ofthe first pat of this book we examine how green buildings fit into abroader based green approach to urban development and redevelopment.

Now is a particularly appropriate time to be addressing the subject ofplants on buildings. Interest in the environment has never been greater.The provision of urban green space is receiving much attention both inEurope and North America. Many local authorities in Britain currentlyhave plans for incorporating nature areas into the urban environment.

However, relatively little attention has been paid to the valuableopportunities represented by buildings and the spaces which relate tothem courtyards, terraces, balconies and so on. This is a great pity,because even in those cities relatively well endowed with green space,many areas can justifiably be regarded as deserts in biological terms.Sealed surfaces of brick, concrete and tarmac are inhospitable to all butthe most opportunistic plants. Each new road, car park, officedevelopment or housing estate results in a further loss of vegetation.Progress equals development is an axiom which shows no sign of beingabandoned, and so we cannot pretend that the impetus of urbandevelopment is likely to slow down in the foreseeable future. Therefore

introduction

We can make choicesabout the surroundings inwhich we live and work.Prosperity and beautyneed not exclude oneanother.

H.R.H. THE PRINCE OFWALES

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we need appropriate development which incorporates an ecologicalapproach to building and landscape design. This means replacing land lostbeneath buildings and roads with a layer of plants on hard surfaces. Bystrategically adding green skins in this way, it is possible to create a newnetwork of vegetation linking roofs, walls, courtyards, streets and openspaces. This is particularly important in the city centres where vegetationmay cover only about one third of the land surface, compared with 75%-95% in the outer suburbs.

It has to be stressed that growing vegetation on hard surfaces shouldnever be viewed a