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Green Roofing Guide
WHAT IS A GREEN ROOF?

A green or ‘living’ roof is essentially the growing of plants on your own rooftops with vegetation layer covering a roof structure, with growing media and plants taking the place of bare membrane, gravel ballast, shingles or tiles. The insulation properties of soil and plants have been utilised by humans for thousands of years, cooling buildings in Africa and helping to retain heat in traditional buildings of Northern Europe and Scandinavia. Green roofs can be anything from a thin growing layer of sedums and mosses to plants, shrubs and water features. They are installed on top of conventional roofs and properly designed, they are stable, living ecosystems that replicate many fo the processes found in nature.

TYPES OF GREEN ROOFS

EXTENSIVE are lightweight, less expensive and low maintenance. Normally less than 6 inches deep growing medium, and, depending depth, may support a range of plants include Sedums (low-growing succulents), and other succulents, flowering herbs, and certain grasses and mosses such as herbs, meadow grasses and perennials. Suitable for use on slopes with up to 30 degree pitch. Steeper ones can be installed with raised grids or laths to hold plants and growing media in place.

INTENSIVE can be thought of as a garden on a roof with lots of shrubs, flowers, even trees along walkways and flowerbeds, is heavier and needs more support and is more expensive. Deeper growing medium can sustain complex landscapes, including small trees and even small ornamental ponds and fountains. Intensive roof greening usually requires irrigation and maintenance, as the roofs have plants of reasonable size for a traditional roof garden.

BIO-DIVERSE OR BROWN a selection of local growing mediums, aggregates, recycled materials and timber, stones normally distributed around the roof surface. This is either left alone to allow the germination of wind-blown seeds, or alternatively, seeds collected from the local area are scattered over the roof area to achieve the biodiversity and recreate the surrounding wildlife habitats. Over time an ecosystem of plants and animals will develop on the roof similar to the local environment. Buildings would need to be designed specifically for this type of system because of the strength requirements of the structure. Where a habitat is being designed to support a specific species, conservationists with normally be consulted to assist in devising a roof-top habitat that will attract and support the target species.

EFFECTS OF GREEN ROOFS

What are the major advantages of green roofs?

Green roofs provide many ecological and aesthetic benefits, including:

  • Controlling water runoff, erosion and pollution
  • Improving water quality
  • Mitigating urban heat-island effects, cooling and cleaning the air
  • More than doubling the service life of the roof
  • Conserving energy
  • Creating wildlife habitat
  • Improving the aesthetic environment in both work and home settings

How does a green roof effect the conventional roof below it?

By covering 100% of the waterproofing materials protecting it from human activity, windblown debris, UV radiation and variations in temperature extremes this minimises damage daily expansion and contraction.

How do Green Roofs affect the building they are on?

By reducing the temperature inside the building on during increasingly hot summer months and thereby reducing costs associated cooling buildings and the need for air conditioning in the summer results in a reduction of CO2 emissions whilst keeping the building cool.

How do Green Roofs affect the quality of life for people?

Where accessible Green Roofs can be used for social and leisure activities and contribute to a greener urban environment and quality of life for communities, particularly in high density areas.

How do Green Roofs affect wildlife?

Because new developments often result in a loss of habitat and Green Roofs create green space in urban areas, they maintain species vital to local biodiversity. In particular they have been to attract many rare invertebrates found on brown field sites, as well as ground nesting birds such as skylarks.

What effect will the winter freeze and thaw cycles have on the roof?

Because not all green roofs are resistant to freeze and thaw cycles care should be taken in the selection of plants and design of the system.

Is there erosion in the winter when the vegetation dies back?

When designing a green roof system it should include a significant percentage of non-deciduous plants, so that the mature cover is never bare of foliage and the potential for erosion is reduced.

PLANT VARIETIES AND GROWING MEDIUM

Plants will vary by region, but generally, the deeper the green roof, the more complex the type of plants that can be sustained. Where frost occurs, half of the plants on an extensive green roof should be varieties of Sedum. In colder climates grass-dominated covers are recommended and tropical plant is not recommended, but other plants can be incorporated to provide habitat value or visual interest.

Are any green roof plants invasive non-natives that could be spread by wind?

Sedum-sarmentosum, also known as Star Sedum, Gold Moss, Stringy Stonecrop or Graveyard Moss has green spearhead-shaped leaves, lemon yellow flowers and long tendrils could be considered invasion and not recommended.

What kind of soil is suitable? Can I just put top soil on my green roof?

Normal gardens oil is heavy and contains undesirable insects and weeds and you do not know what’s in it. growing mediums need to be lightweight, drain properly but retain a certain amount of rain water.

Are green roofs necessarily green in colour?

Many green roofs appear red, orange, yellow and all colours in between at different times of the year because the fleshy leaves of various succulents change colours throughout the year. This can lead to anticipation with the variation flower colours from whites to yellow, pinks, deep reds and purples and blues creating a virtual living carpet or tapestry varies from season to season.

Can green roofs be combined with other green features?

Green roofs can be designed in conjunction with solar panels and in combination with other ‘low-impact’ development measures, such as infiltration beds, rain gardens, bio-retention systems, cisterns and rain barrels.

How are green roof plants started?

There are several methods for starting green roof plantings. Perennials can be seeded or may be established from fresh cuttings or from plugs planted a foot apart.

Can I plant vegetable garden on my green roof?

Generally, green roof systems are not deep enough for growing vegetables and the tools of traditional gardening would damage the green roof and the underlaying waterproofing. However, incorporating container gardens or modular elements  can accommodate and owners desires.

Where can I buy seeds to plant my own green roof?

We can either supply plants or seed or advise you where to buy them.

What about pre-planted modules

Apart from planting seeds of plugs you can buy ready planted modules that are 500mm x 500mm x 50mm depth with water retaining cuplets, incorporating drainage holes. These overlap with adjoining modules by 100mm and interlock into overlapping cuplets to provide an instant green roof finish.

How long until the green roof will be fully covered?

Generally, a green roof that is planted correctly will reach maturity in two growing seasons, or less. Depending on the level of sun or rain may slow the process. However, pre-grown Sedum mats, can be used for an instant garden finish.

Will ordinary grass or grass sods be suitable for a green roof?

Historically people used the materials close at hand for hundreds of years in many parts of the world. A monoculture of plant species is not considered healthy or desirable for roof garden systems because it could be open to plant disease or insect infestation. Ideally plant varieties should be ecologically diverse, with many types of vegetation to be vibrant and healthy. Grass or grass sod needs to be watered, fertilised and cut regularly, so they would incur greater costs for maintenance.

DESIGN AND CONSTRUCTION

What if my roof isn’t flat?

The term flat roof is a contradiction and it needs to allow water to flow off the surface and therefore should not be actually be flat. Most green systems can be laid to a pitch of 40 degrees quite comfortably with the help of retention bar to prevent slippage with allowing excess water to drain through.

What are the most important factors in designing a green roof?

  • Climate, especially temperature and rainfall patterns
  • Strength of the supporting structure
  • Size, slope, height and direction of the roof
  • Type of underlying waterproofing
  • Drainage elements, such as drains, scruppers and drainage conduits
  • Accessibility and intended use
  • Visibility, fit with architecture and owners aesthetic preferences
  • Fit with other green systems such as solar panels
  • Cost of materials and labour

Are leaks under a conventional green roof a problem?

Leaks in the waterproofing layer are less likely when it is protected from the elements by a green roof. is a leak does occur, it can readily be located by using new and more reliable electronic technology which can quickly and accurately pinpoint problems. Repairs to the waterproofing are quick and disturbance of the green roof is minimal.

Do green roofs cause leaks? 

Only poor installation or incorrect specification of the waterproofing materials can result in leaks on green roofed building. When installing a green roof onto an existing building, care must be taken not to damage the existing roofing material and a ‘root-resistant’ element is installed.

Is attaching all elements of green roof to the underlying structure important?

Plant roots bind the layers of media and fabrics to create a unified cover, and the plants themselves create enough surface wind turbulence to reduce potential wind uplift. If the green roof is to be located in an unusually high wind area, such as a high rise building or coastal area it may be appropriate to use ballast.

How steeply pitched can the roof be?

The maximum slope recommended for conventional green roofs is 30 degrees pitch. If roofs have a pitch greater than 30 degrees, special techniques are required.

What kind of waterproofing do I need?

Many types of waterproofing are compatible with green roofs. Mastic Asphalt, bituminous membranes, single ply and liquid coatings are the most common. With the exception of Mastic Asphalt, which because it’s close texture will not permit penetration it is necessary to have the final layer which is root-resistant for all types of green roofs to avoid the risk of roots penetrating the waterproofing.

What guarantees do manufacturers offer?

Waterproofing manufacturers offer varying lengths of guarantees dependant on products and systems and when it is installed by an approved contractor. There are some guarantees for the green roofs plant element.

How do green roofs effect the life span of a roof?

The lifespan of a standard roofing material in good condition is at least doubled by the addition of a green roof by protecting the membrane from corrosive UV rays and temperature fluctuations which occur throughout the day.

In what climates do green roofs work?

Green roofs have been built most wildly in temperature climates, but special techniques allow them to thrive in semi-arid, tropical and even windy coastal areas, and have been installed from hot, moist to cold and windy locations.

Can recycled materials be used is constructing green roofs?

Recycled materials can be used and their use should be considered in the design to reduce the use of virgin materials. Recycled materials are particularly suitable in Bio-diverse or Brown systems.

Is my roof strong enough to support a green roof?

Green roofs vary greatly in weight, depending on their depth and the materials used. The important measurement is ‘wet’ weight which could be about 60-150kg square metre.

Calculations should take into account the weight of water help in the soil and any snow loading.

Does a green roof weigh more than a traditional roof?

A green roof weighs more than a conventional roof due to the weight of substrate, vegetation and their water and can be easily factored into the structural design of a new development.  Existing buildings can be retrofitted with a green roof, but may need to be reinforced to take the additional weight.

Do I need to consult a structural engineer?

It is always advisable to contact a structural engineer or discussed the design with building control to ensure they are satisfied with the nature of the work.

Does a green roof require planning permission?

It is always advisable to check with the local planning department who will advise you on what steps should be taken.

Can a green roof help me get planning permission?

Green roofs improve the aesthetics of a building, especially when the planted with flowers, with small blooms of yellow, pink, white and red flowers at different times of the year. These aesthetic qualities may help when applying for planning permission for new buildings because it actively removes pollutants from new site whilst disguising or hiding new development.

Do I need building regulation approval?

When replacing an existing roof with a green system you will not normally need building regulations approval with the exception meeting new thermal regulations. If it is a new roof you will need approval.

FIRE

Are green roofs a fire risk? Is there a danger of dry plants catching and spreading fire? 

By choosing plants that store water in the stems and are inherently non-flammable, coupled with gravel boarders and breaks protect against fire to create a better fire rating than conventional roofs if designed correctly.

COSTS AND FINANCIAL IMPLICATIONS

How much does a green roof cost? 

Costs depend on many factors: the size and slope of the roof, depth and complexity of the system, height and accessibility from the ground, cost of labour, and need for specialist elements, such as drains, railings, pavers, slope stabilisation measures etc.

Us there any funding available to install a green roof?

There is currently no government funding or incentives available specifically for green roof installation in the UK. However, it is sometimes possible to win funding for outcomes such as habitat replacement/introduction or urban agriculture, and then apply it to a roof space.

What financial benefits do green roofs provide?

Because years of experience throughout the world have shown that a green roof can be expected to outlast a comparable ‘normal’ roof by a factor or at least two, and often three years, this goes a long way toward tying back the initial investment in a green roof.

Will a green roof reduce energy costs?

Acting as a heat sink, slowly absorbing and holding energy from sunlight and releasing it when the ambient air Colls, this acts as a heat ‘storage battery’ and reduces the heating and cooling demands within the building.

INSULATION AND 'U' VALUES

What is the typical U-Value of a green roof?

No specific thermal value is given to the green roof itself but current regulations must be achieved by using the correct insulation within the roof construction itself. The roof will however benefit from increased protection from heat in the Sumer and some protection from cold in the winter. We can provide you with the appropriate calculations to meet the requirements.

Sound insulation

Green roofs help reduce noise and are good in high noise areas such as near airports or where noise reduction is required for example hospitals, respite homes etc.

MAINTENANCE

Who should maintain my roof?

Whilst maintenance should be minimal for most green roofs, homeowners should check a flat or low pitch green roof if access is good and does not present a danger. Where the project is too large or an intensive roof system installed then a roofing professional should be recruited to provide a maintenance service of at least twice per year.

What kind of maintenance is required and is an extensive green roof really maintenance-free?

Regard how drought tolerant plants green roofs should be monitored and checked periodically for invasive weeds, disease, etc and to occasionally infill of plants. Maintenance visits should be timed to intercept any weeds before they go to seed to maintain the health of plants and protect the underlying roofing materials.

Will I be able to walk on my green roof? Can it be used for recreation?

Where the roof is accessible from the building and it will support the weight of decks, patios and walkway pavers can be integrated into the design of the green roof. Care must be taken with the selection of plants and only turf grass will stand up to regular foot traffic. Alternatively, if more fragile plants are installed then stepping stones or walkways can be used to provide access through green roofs.

Is access to the roof needed?

Every green roof requires some degree of maintenance to ensure it is kept in top condition, so providing provision for access at an early stage is always beneficial. Health and Safety regulations require anyone within 2m of a roof edge to wear a safety harness. Brackets, man safe systems, edging or fall nets can all provide attachment points and protection from falls.

Do I have to mow my green roof?

Sedum systems never grow beyond a few centimetres in height and never need mowing. If you choose a grass or wildflower systems, when strimming is recommended at the end of the growing season once the seeds have self-sown.

Do I have to water my green roof?

Extensive 

If you have chosen the correct drought tolerant plants the there should be no need to water except in extreme periods of drought other than the first year whilst plant systems become established. For large projects some from of drip irrigations which is inexpensive and delivers the correct amount of water to the base of the plats will be ideal.

Intensive

Because an intensive green roof can be a combination of a large variety of plants, shrubs and trees and their watering requirements will be much higher than succulents and herbs. It should be treated like any ground level garden or landscape and watering should take into account the drying effect of high winds. Usually large intensive green roof projects have an irrigation system installed that can be environmentally friendly using a traditional active irrigation system or a solar powered stems and recycled rain water collection system and you’ve go the ideal self-sustainable supplemental water system.

Bio-diverse or Brown

The basis of this type of roof is to allow nature to take over naturally.

Is irrigation required? If so, what kind?

With thoughtful planning irrigation is rarely necessary. When irrigation is required, the water should be delivered deep under the surface – where the roots will seek it and it will not be lost to evaporation. Surface irrigation systems are wasteful and require more maintenance than subsurface irrigation methods.

How do Green Roofs affect water drainage from the roof?

Research indicated that Green Roofs reduce annual run-off roofs by at least 50% contributing to urban drainage and flood alleviation schemes. The rate of release following heavy rainfall is slowed, reducing the problems associated with storm surges.

Should I fertilise my extensive green roof?

There is some argument about whether this necessary for fertilise a green roof. It is probably preferable to encapsulated slow release fertiliser during the first year of establishment in spring and autumn. After that the natural cycle should take over and enough organic material should have composted itself back into the soil substrate to provide sufficient nutrients to the plants.

Green Roofing Guide
WHAT IS A GREEN ROOF?

A green or ‘living’ roof is essentially the growing of plants on your own rooftops with vegetation layer covering a roof structure, with growing media and plants taking the place of bare membrane, gravel ballast, shingles or tiles. The insulation properties of soil and plants have been utilised by humans for thousands of years, cooling buildings in Africa and helping to retain heat in traditional buildings of Northern Europe and Scandinavia. Green roofs can be anything from a thin growing layer of sedums and mosses to plants, shrubs and water features. They are installed on top of conventional roofs and properly designed, they are stable, living ecosystems that replicate many fo the processes found in nature.

TYPES OF GREEN ROOFS

EXTENSIVE are lightweight, less expensive and low maintenance. Normally less than 6 inches deep growing medium, and, depending depth, may support a range of plants include Sedums (low-growing succulents), and other succulents, flowering herbs, and certain grasses and mosses such as herbs, meadow grasses and perennials. Suitable for use on slopes with up to 30 degree pitch. Steeper ones can be installed with raised grids or laths to hold plants and growing media in place.

INTENSIVE can be thought of as a garden on a roof with lots of shrubs, flowers, even trees along walkways and flowerbeds, is heavier and needs more support and is more expensive. Deeper growing medium can sustain complex landscapes, including small trees and even small ornamental ponds and fountains. Intensive roof greening usually requires irrigation and maintenance, as the roofs have plants of reasonable size for a traditional roof garden.

BIO-DIVERSE OR BROWN a selection of local growing mediums, aggregates, recycled materials and timber, stones normally distributed around the roof surface. This is either left alone to allow the germination of wind-blown seeds, or alternatively, seeds collected from the local area are scattered over the roof area to achieve the biodiversity and recreate the surrounding wildlife habitats. Over time an ecosystem of plants and animals will develop on the roof similar to the local environment. Buildings would need to be designed specifically for this type of system because of the strength requirements of the structure. Where a habitat is being designed to support a specific species, conservationists with normally be consulted to assist in devising a roof-top habitat that will attract and support the target species.

EFFECTS OF GREEN ROOFS

What are the major advantages of green roofs?

Green roofs provide many ecological and aesthetic benefits, including:

  • Controlling water runoff, erosion and pollution
  • Improving water quality
  • Mitigating urban heat-island effects, cooling and cleaning the air
  • More than doubling the service life of the roof
  • Conserving energy
  • Creating wildlife habitat
  • Improving the aesthetic environment in both work and home settings

How does a green roof effect the conventional roof below it?

By covering 100% of the waterproofing materials protecting it from human activity, windblown debris, UV radiation and variations in temperature extremes this minimises damage daily expansion and contraction.

How do Green Roofs affect the building they are on?

By reducing the temperature inside the building on during increasingly hot summer months and thereby reducing costs associated cooling buildings and the need for air conditioning in the summer results in a reduction of CO2 emissions whilst keeping the building cool.

How do Green Roofs affect the quality of life for people?

Where accessible Green Roofs can be used for social and leisure activities and contribute to a greener urban environment and quality of life for communities, particularly in high density areas.

How do Green Roofs affect wildlife?

Because new developments often result in a loss of habitat and Green Roofs create green space in urban areas, they maintain species vital to local biodiversity. In particular they have been to attract many rare invertebrates found on brown field sites, as well as ground nesting birds such as skylarks.

What effect will the winter freeze and thaw cycles have on the roof?

Because not all green roofs are resistant to freeze and thaw cycles care should be taken in the selection of plants and design of the system.

Is there erosion in the winter when the vegetation dies back?

When designing a green roof system it should include a significant percentage of non-deciduous plants, so that the mature cover is never bare of foliage and the potential for erosion is reduced.

PLANT VARIETIES AND GROWING MEDIUM

Plants will vary by region, but generally, the deeper the green roof, the more complex the type of plants that can be sustained. Where frost occurs, half of the plants on an extensive green roof should be varieties of Sedum. In colder climates grass-dominated covers are recommended and tropical plant is not recommended, but other plants can be incorporated to provide habitat value or visual interest.

Are any green roof plants invasive non-natives that could be spread by wind?

Sedum-sarmentosum, also known as Star Sedum, Gold Moss, Stringy Stonecrop or Graveyard Moss has green spearhead-shaped leaves, lemon yellow flowers and long tendrils could be considered invasion and not recommended.

What kind of soil is suitable? Can I just put top soil on my green roof?

Normal gardens oil is heavy and contains undesirable insects and weeds and you do not know what’s in it. growing mediums need to be lightweight, drain properly but retain a certain amount of rain water.

Are green roofs necessarily green in colour?

Many green roofs appear red, orange, yellow and all colours in between at different times of the year because the fleshy leaves of various succulents change colours throughout the year. This can lead to anticipation with the variation flower colours from whites to yellow, pinks, deep reds and purples and blues creating a virtual living carpet or tapestry varies from season to season.

Can green roofs be combined with other green features?

Green roofs can be designed in conjunction with solar panels and in combination with other ‘low-impact’ development measures, such as infiltration beds, rain gardens, bio-retention systems, cisterns and rain barrels.

How are green roof plants started?

There are several methods for starting green roof plantings. Perennials can be seeded or may be established from fresh cuttings or from plugs planted a foot apart.

Can I plant vegetable garden on my green roof?

Generally, green roof systems are not deep enough for growing vegetables and the tools of traditional gardening would damage the green roof and the underlaying waterproofing. However, incorporating container gardens or modular elements  can accommodate and owners desires.

Where can I buy seeds to plant my own green roof?

We can either supply plants or seed or advise you where to buy them.

What about pre-planted modules

Apart from planting seeds of plugs you can buy ready planted modules that are 500mm x 500mm x 50mm depth with water retaining cuplets, incorporating drainage holes. These overlap with adjoining modules by 100mm and interlock into overlapping cuplets to provide an instant green roof finish.

How long until the green roof will be fully covered?

Generally, a green roof that is planted correctly will reach maturity in two growing seasons, or less. Depending on the level of sun or rain may slow the process. However, pre-grown Sedum mats, can be used for an instant garden finish.

Will ordinary grass or grass sods be suitable for a green roof?

Historically people used the materials close at hand for hundreds of years in many parts of the world. A monoculture of plant species is not considered healthy or desirable for roof garden systems because it could be open to plant disease or insect infestation. Ideally plant varieties should be ecologically diverse, with many types of vegetation to be vibrant and healthy. Grass or grass sod needs to be watered, fertilised and cut regularly, so they would incur greater costs for maintenance.

DESIGN AND CONSTRUCTION

What if my roof isn’t flat?

The term flat roof is a contradiction and it needs to allow water to flow off the surface and therefore should not be actually be flat. Most green systems can be laid to a pitch of 40 degrees quite comfortably with the help of retention bar to prevent slippage with allowing excess water to drain through.

What are the most important factors in designing a green roof?

  • Climate, especially temperature and rainfall patterns
  • Strength of the supporting structure
  • Size, slope, height and direction of the roof
  • Type of underlying waterproofing
  • Drainage elements, such as drains, scruppers and drainage conduits
  • Accessibility and intended use
  • Visibility, fit with architecture and owners aesthetic preferences
  • Fit with other green systems such as solar panels
  • Cost of materials and labour

Are leaks under a conventional green roof a problem?

Leaks in the waterproofing layer are less likely when it is protected from the elements by a green roof. is a leak does occur, it can readily be located by using new and more reliable electronic technology which can quickly and accurately pinpoint problems. Repairs to the waterproofing are quick and disturbance of the green roof is minimal.

Do green roofs cause leaks? 

Only poor installation or incorrect specification of the waterproofing materials can result in leaks on green roofed building. When installing a green roof onto an existing building, care must be taken not to damage the existing roofing material and a ‘root-resistant’ element is installed.

Is attaching all elements of green roof to the underlying structure important?

Plant roots bind the layers of media and fabrics to create a unified cover, and the plants themselves create enough surface wind turbulence to reduce potential wind uplift. If the green roof is to be located in an unusually high wind area, such as a high rise building or coastal area it may be appropriate to use ballast.

How steeply pitched can the roof be?

The maximum slope recommended for conventional green roofs is 30 degrees pitch. If roofs have a pitch greater than 30 degrees, special techniques are required.

What kind of waterproofing do I need?

Many types of waterproofing are compatible with green roofs. Mastic Asphalt, bituminous membranes, single ply and liquid coatings are the most common. With the exception of Mastic Asphalt, which because it’s close texture will not permit penetration it is necessary to have the final layer which is root-resistant for all types of green roofs to avoid the risk of roots penetrating the waterproofing.

What guarantees do manufacturers offer?

Waterproofing manufacturers offer varying lengths of guarantees dependant on products and systems and when it is installed by an approved contractor. There are some guarantees for the green roofs plant element.

How do green roofs effect the life span of a roof?

The lifespan of a standard roofing material in good condition is at least doubled by the addition of a green roof by protecting the membrane from corrosive UV rays and temperature fluctuations which occur throughout the day.

In what climates do green roofs work?

Green roofs have been built most wildly in temperature climates, but special techniques allow them to thrive in semi-arid, tropical and even windy coastal areas, and have been installed from hot, moist to cold and windy locations.

Can recycled materials be used is constructing green roofs?

Recycled materials can be used and their use should be considered in the design to reduce the use of virgin materials. Recycled materials are particularly suitable in Bio-diverse or Brown systems.

Is my roof strong enough to support a green roof?

Green roofs vary greatly in weight, depending on their depth and the materials used. The important measurement is ‘wet’ weight which could be about 60-150kg square metre.

Calculations should take into account the weight of water help in the soil and any snow loading.

Does a green roof weigh more than a traditional roof?

A green roof weighs more than a conventional roof due to the weight of substrate, vegetation and their water and can be easily factored into the structural design of a new development.  Existing buildings can be retrofitted with a green roof, but may need to be reinforced to take the additional weight.

Do I need to consult a structural engineer?

It is always advisable to contact a structural engineer or discussed the design with building control to ensure they are satisfied with the nature of the work.

Does a green roof require planning permission?

It is always advisable to check with the local planning department who will advise you on what steps should be taken.

Can a green roof help me get planning permission?

Green roofs improve the aesthetics of a building, especially when the planted with flowers, with small blooms of yellow, pink, white and red flowers at different times of the year. These aesthetic qualities may help when applying for planning permission for new buildings because it actively removes pollutants from new site whilst disguising or hiding new development.

Do I need building regulation approval?

When replacing an existing roof with a green system you will not normally need building regulations approval with the exception meeting new thermal regulations. If it is a new roof you will need approval.

FIRE

Are green roofs a fire risk? Is there a danger of dry plants catching and spreading fire? 

By choosing plants that store water in the stems and are inherently non-flammable, coupled with gravel boarders and breaks protect against fire to create a better fire rating than conventional roofs if designed correctly.

COSTS AND FINANCIAL IMPLICATIONS

How much does a green roof cost? 

Costs depend on many factors: the size and slope of the roof, depth and complexity of the system, height and accessibility from the ground, cost of labour, and need for specialist elements, such as drains, railings, pavers, slope stabilisation measures etc.

Us there any funding available to install a green roof?

There is currently no government funding or incentives available specifically for green roof installation in the UK. However, it is sometimes possible to win funding for outcomes such as habitat replacement/introduction or urban agriculture, and then apply it to a roof space.

What financial benefits do green roofs provide?

Because years of experience throughout the world have shown that a green roof can be expected to outlast a comparable ‘normal’ roof by a factor or at least two, and often three years, this goes a long way toward tying back the initial investment in a green roof.

Will a green roof reduce energy costs?

Acting as a heat sink, slowly absorbing and holding energy from sunlight and releasing it when the ambient air Colls, this acts as a heat ‘storage battery’ and reduces the heating and cooling demands within the building.

INSULATION AND 'U' VALUES

What is the typical U-Value of a green roof?

No specific thermal value is given to the green roof itself but current regulations must be achieved by using the correct insulation within the roof construction itself. The roof will however benefit from increased protection from heat in the Sumer and some protection from cold in the winter. We can provide you with the appropriate calculations to meet the requirements.

Sound insulation

Green roofs help reduce noise and are good in high noise areas such as near airports or where noise reduction is required for example hospitals, respite homes etc.

MAINTENANCE

Who should maintain my roof?

Whilst maintenance should be minimal for most green roofs, homeowners should check a flat or low pitch green roof if access is good and does not present a danger. Where the project is too large or an intensive roof system installed then a roofing professional should be recruited to provide a maintenance service of at least twice per year.

What kind of maintenance is required and is an extensive green roof really maintenance-free?

Regard how drought tolerant plants green roofs should be monitored and checked periodically for invasive weeds, disease, etc and to occasionally infill of plants. Maintenance visits should be timed to intercept any weeds before they go to seed to maintain the health of plants and protect the underlying roofing materials.

Will I be able to walk on my green roof? Can it be used for recreation?

Where the roof is accessible from the building and it will support the weight of decks, patios and walkway pavers can be integrated into the design of the green roof. Care must be taken with the selection of plants and only turf grass will stand up to regular foot traffic. Alternatively, if more fragile plants are installed then stepping stones or walkways can be used to provide access through green roofs.

Is access to the roof needed?

Every green roof requires some degree of maintenance to ensure it is kept in top condition, so providing provision for access at an early stage is always beneficial. Health and Safety regulations require anyone within 2m of a roof edge to wear a safety harness. Brackets, man safe systems, edging or fall nets can all provide attachment points and protection from falls.

Do I have to mow my green roof?

Sedum systems never grow beyond a few centimetres in height and never need mowing. If you choose a grass or wildflower systems, when strimming is recommended at the end of the growing season once the seeds have self-sown.

Do I have to water my green roof?

Extensive 

If you have chosen the correct drought tolerant plants the there should be no need to water except in extreme periods of drought other than the first year whilst plant systems become established. For large projects some from of drip irrigations which is inexpensive and delivers the correct amount of water to the base of the plats will be ideal.

Intensive

Because an intensive green roof can be a combination of a large variety of plants, shrubs and trees and their watering requirements will be much higher than succulents and herbs. It should be treated like any ground level garden or landscape and watering should take into account the drying effect of high winds. Usually large intensive green roof projects have an irrigation system installed that can be environmentally friendly using a traditional active irrigation system or a solar powered stems and recycled rain water collection system and you’ve go the ideal self-sustainable supplemental water system.

Bio-diverse or Brown

The basis of this type of roof is to allow nature to take over naturally.

Is irrigation required? If so, what kind?

With thoughtful planning irrigation is rarely necessary. When irrigation is required, the water should be delivered deep under the surface – where the roots will seek it and it will not be lost to evaporation. Surface irrigation systems are wasteful and require more maintenance than subsurface irrigation methods.

How do Green Roofs affect water drainage from the roof?

Research indicated that Green Roofs reduce annual run-off roofs by at least 50% contributing to urban drainage and flood alleviation schemes. The rate of release following heavy rainfall is slowed, reducing the problems associated with storm surges.

Should I fertilise my extensive green roof?

There is some argument about whether this necessary for fertilise a green roof. It is probably preferable to encapsulated slow release fertiliser during the first year of establishment in spring and autumn. After that the natural cycle should take over and enough organic material should have composted itself back into the soil substrate to provide sufficient nutrients to the plants.