Tel: 0800 061 2835 mark@enviromat.co.uk www.maintenanceforgreenroofs.com

Green Roofs:

Designing for Maintenance

Green Roofs are becoming more mainstream. In some

UK cities, planners are being encouraged to introduce as

many living roofs as possible on to new buildings, from

green roofed bicycle sheds in the gardens of social hous-

ing to vast biodiverse roofs on commercial warehousing.

Enviromat work closely with the UK’s leading green roof

installation company; growing their sedum matting and

helping to research and develop new ways of

establishing plants on to green roofs of all shapes and

sizes.

The knowledge and experience gained in over a decade

of working with green roof plants and substrates is

shared with Enviromat’s green roof maintenance

division who work with green roofing companies and

their clients to ensure that the nation’s green roofs are

performing as well as they possibly can.

Besides a general lack of awareness for the value of, and

indeed the need for, green roof maintenance. By far

the biggest difficulty encountered by the Enviromat

green roof maintenance team is a lack of foresight at

the design stage. This document aims to remind anyone

who designs green roofed buildings of the basic needs

of the green roof maintenance operatives who will be

keeping the roof in good condition for years to come.

Mark Pawsey, Green Roof Supervisor at Enviromat

believes strongly that regular maintenance to keep

green roof plants in robust health really does

maximize all of the benefits of the living roof. More

importantly, he is convinced that maintenance

programs should be affordable...and that careful

consideration at the design stage can keep

maintenance costs under control

A HEALTHY GREEN ROOF IS AN ASSET

TO A BUILDING

Budget:

Clients should be made aware at the planning stage that a living green roof

needs annual maintenance if it is to perform as expected. Many of the

commercial green roof installers do include a period of maintenance in

their contract so that they can ensure plants have established before the

project is signed off; however, on-going maintenance is essential and the

client should include it in their annual buildings maintenance budget.

Maintenance costs vary according to access, planting plan, size of the roof

and it’s condition but a ballpark figure can be obtained from Mark Pawsey

at Enviromat. Email mark@enviromat.co.uk

An extensive green roof is

“low maintenance” not

“no maintenance” clients

should budget for two

maintenance visits per

annum

Loadings:

When calculating loadings on the building, please factor in the saturated weight of the growing medium, the living plants, any

edgings, fixings and fall restraints and also, live loading for at least two people to walk on the roof twice a year.

Slopes and Drainage:

Two very important factors; Slope affects anchorage, access for

maintenance and also drainage. Good drainage is a must BUT, if it’s too

good (as in a steep slope) water will drain away before the plants can

benefit from it. If your roof slope is greater than 10 degrees, you would

be well advised to install an irrigation system and budget for at least

three maintenance visits per annum.

Be aware that water directed on to a green roof from other buildings can

potentially damage plants and if your design includes paths or walkways,

please ensure that these don’t adversely affect the drainage.

A steep slope is visually attractive but can be

a challenge to maintain.

Designing Green Roofs with maintenance in mind:

Budgets and Buildings

E n v i r o m a t

Well designed drainage outlets do not

allow debris to fall into the gutters and

are easy to clear Inadequate drainage will damage plant

populations

Health and Safety:

Health and Safety is not just for the installation stage of your green roof. It’s for

maintenance too. Safe access points and fall restraints are essential please;

Enviromat’s green roof maintenance team have our own safety clothing but we

do appreciate having anchorage points for our harnesses and lanyards.

Access:

This is one of the most common challenges for our operatives. People and equipment need to get on to the roof, and,

depending on the aspect and the planting plan, there may be debris to be carried down from the roof. If at all possible, an

internal staircase, or a fixed external ladder with fall restraints would be superb. On a large roof, operatives are required to

carry bags of plant food on to the roof…a winch system makes life much easier for them and also makes the job quicker…

ultimately saving on labour costs.

Water:

Green roof plants will need to be watered in the first few weeks of establishment, and may also need irrigation during ex-

treme drought and immediately after feeding. Choosing drought tolerant plants and the correct depth of growing medium

will considerably reduce the need for irrigation once the roof is established but please include a functioning water tap

somewhere in your design.

The result of inadequate maintenance on a sedum

roof.

Plant coverage has been lost...probably due to

lack of nutrients.

With no foliage to shade it from the sun, the

growing medium has dried out and will not be

effective at cooling the building in hot weather

Without the plants’ roots to stablilise it, growing

medium is easily washed into drains during a

rainstorm

Poor plant coverage or unhealthy plants are of

little benefit to wildlife; neither are they a pretty

sight

Designing Green Roofs with maintenance in mind:

Budgets and Buildings

E n v i r o m a t

Designing Green Roofs with maintenance in mind:

Plant Choices

E n v i r o m a t

Plant Choices

A green roof is a marriage between engineering and ecology. These are two disciplines

that don’t necessarily join forces in any other situation and so green roofing is a bit of a

learning curve for both.

Choosing green roof plants is a juggling act between the client’s expectations for

aesthetics, speed of establishment, budget and ability to care for the plants; planning

requirements such as local biodiversity action plans; local environment and growing

conditions on the roof.

If the conditions created by the engineering of a building are wrong for a particular plant species, it will be very difficult to

keep those plants in good health. If the plants are inappropriate for green roofing, the building may be damaged.

When choosing plants think of a green roof as a giant container garden and consider the following:

Depth of growing medium:

This will affect loadings on the building, but it is also vital that the chosen plants have enough growing

medium (substrate) to support them.

Sedums can survive in just 20mm of growing medium; a wild flower meadow will need at least 150mm.

Bear in mind too, the method of establishment…sedum blankets need no extra growing medium,

sedum plug plants will need to be planted into at least 100mm depth of substrate.

The deeper the substrate…the more likely it is to support unwanted plant species…so more weeding

for the maintenance team.

Mixed sedum plants

Aspect:

Some plants detest shade, others embrace it. If you have an area that’s likely to be in permanent shade – eg behind PV pan-

els, either make sure there is enough growing medium to support shade loving plants OR plan to have a plant-free area here.

In a sunny spot, make sure you choose plants that can tolerate intense summer heat as well as winter cold. Never forget that

the temperature on a roof is usually and exaggerated version of the temperature on the ground. Hotter in summer, colder in

winter.

Surrounding area:

If your green roof is in close proximity to deciduous trees, you will need to remove fallen leaves in the autumn time. Please

budget for this annual task and ensure debris can be removed from the roof safely.

Height of the building:

Altitude will have a bearing on wind speeds and ambient temperature; remember that even a slight breeze can dry out plants

in a remarkably short time. Look for low growing drought tolerant plants that are not likely to be buffeted about or scorched

by strong winds.

Mode of establishment:

Green roofs that are seeded or plug planted are likely to need more maintenance in the first 2-3 years than green roofs

created with vegetation mats: this is because gaps between the plants are a great place for weeds to establish. Where there is

complete plant coverage it is more difficult for unwanted plant species to invade.

Plant vigour:

Some plants are just too vigorous for green roofing, avoid anything with invasive root systems as they may damage

waterproofing. Be sure too that no one species is likely to out-compete everything else on the roof.

Mixing species

Wherever possible incorporate a mixture of plant species and varieties.

Even if biodiversity is not the primary reason for installing a green roof, it

is an important feature of any green space.

Incorporating several different species will mean that there is less risk of

all plants being wiped out by pests, diseases or bad weather; it will also

mean (hopefully) that there is a longer flowering period offering greater

benefits to pollinating insects and of course, more visual interest.

Mixed native species are an excellent choice for green roofing. Ideally

look for perennial plants (not all annuals will seed themselves successfully

year after year) that flower at different times of the year and provide a

source of nectar for as long a period as possible. Avoid really grassy

meadow-type mixes unless you are able to cut them back once a year and

remove all the clippings from the roof.

Low maintenance plants

Generally speaking, if a plant is happy in it’s situation, it won’t need a lot

of TLC but some types of planting will always need more maintenance

than others. If you are using your green roof to cultivate food crops, grow

shrubs, exotic plants or tender perennials, be prepared for extra

maintenance.

Meadow saxifrage; an early flowering native

plant ideal for use on green roofs.

This grassy roof is great for insulation, rainwater

management and biodiversity but at least once

a year it will need to be mown and have all the

clippings removed. OK on a single storey

structure like this but no so convenient on a

very tall building.

Designing Green Roofs with maintenance in mind:

Plant Choices

E n v i r o m a t

A stitch in time saves nine:

Nine compelling reasons to look after your green roof

1. Regular check-ups can spot problems with the visible

roof structure before they get expensive

2. Each layer of a green roof interacts with the other

constituents to form a dynamic system. A seemingly small problem in one area could

be detrimental to the whole roof if it is not addressed quickly enough.

3. It’s cheaper to spend a little every year to keep the green roof build up in good order

than it is to replace the whole thing when it fails.

4. A well maintained, healthy green roof will reduce the buildings’ energy usage, saving

money and reducing carbon emissions

5. A neglected green roof is unattractive and gives a bad impression.

6. A vibrant and well functioning green roof soon becomes a mini wildlife sanctuary. Our

experts can give you tips on developing your green roof to increase biodiversity.

7. A well functioning green roof could improve productivity by reducing sick building

syndrome

8. Unwanted plants such as tree seedlings establishing themselves in the growing

medium could damage the structure of the building if they are not removed as part of

a regular green roof maintenance regime.

9. A healthy, attractive, well functioning green roof can increase property values.

Designing Green Roofs with maintenance in mind:

How Regular Maintenance Maximises Performance

E n v i r o m a t

Designing Green Roofs with maintenance in mind:

Troubleshooting

E n v i r o m a t

Sedum matting on a green roof has not established

because of lack of water. This can be remedied in one

or two maintenance visits but it would have been

cheaper to ensure that it is easy to irrigate the roof

at the

Weeds will establish themselves if the desired

planting is not in the best of health. Choosing robust

plants that are well adapted to the microclimate and

then keeping them in good heart will help keep

weeds at bay.

Expect a healthy green roof to change its

appearance with the seasons. This cherry red

colour is normal for a sedum roof in winter.

It’s important to get drainage right before the green

roof build up is installed. Be wary of drains

discharging on to the roof. In this instance, the sedum

plants are not tolerating the wet conditions.

Designing Green Roofs with maintenance in mind:

Useful Contacts

E n v i r o m a t

For help and advice with designing a

large scale or commercial green roof:

Please contact Bauder

http://www.bauder.co.uk/green-roofs

Tel: 0845 271 8800

For information about Enviromat’s

Green Roof Maintenance Service

Please contact Mark Pawsey on 07787 288736,

Email mark@enviromat.co.uk

Or visit our web site

www.maintenanceforgreenroofs.com

For help and advice with designing a small scale domestic green roof:

Please contact Enviromat

www.enviromat.co.uk

Tel: 0800 061 2835

Or visit our blog at http://greenroofsforordinaryfolk.blogspot.co.uk/