September 2008 - green roofs | solar pv | single ply roofing · variations but in general green roofs have ... an extensive green roof are visual, ... Insulated intensive green roof

Extensive and Intensive Green Roof Technology

SfB 47

September 2008

In general a green roof is one with plantsgrowing on its surface. This can rangefrom the spontaneous occurrence of lichenand moss on a roof surface to a fullylandscaped space including trees, shrubsand hard landscaping. There are manyvariations but in general green roofs havebeen divided into extensive, intensive andbrown.

ExtensiveExtensive green roofs have lowmanagement requirements and do notusually require artificial irrigation. Basedon thin soil or substrate layers, plantingstyles are naturalistic with the object ofestablishing a self-sustaining plantcommunity, such as sedums or hardywildflower mixtures. An alternative isAxter’s HYDROPACK ready plantedmodular tray (see separate HYDROPACKbrochure). The main reasons for installingan extensive green roof are visual,creating habitat for native flora and fauna,and enhancing the building performance.

IntensiveIntensive green roofs need similarmanagement to a ground level garden, usuallycomprise a deep soil or growing medium andrequire artificial irrigation.They can be adaptedto accommodate virtually any type of plant and often include hard surfaces for access. The main reason for installing an intensivegreen roof is to provide amenity space.

Brown roofsIt is possible to replicate, on the roof, theenvironmentally diverse brown field sitesassociated with demolished buildings. In thisway building rubble can be easily recycledand vegetation associated with such sites cancolonise a range of low-fertility substrates, i.e.rubble, sand, rotting timber, etc.

Axter specialises in the design of green roofsand in conjunction with horticultural experts willproduce bespoke design specifications foreach construction, covering all aspects ofwaterproofing and insulation, watermanagement and hard and soft surfacing.

ENVIRONMENTAL BENEFITS

Depending upon the type of roof gardenrequired the advantages include:

◆ Improved rainwater management◆ Use of roof area as additional space◆ Visually attractive with a range of

plants and foliage effects◆ Low maintenance (extensive roofs

only) with little or no artificialirrigation

◆ Improved thermal performance◆ Reduction in sound transmission

through the roof◆ Improvement in air quality through

absorption of carbon dioxide andrelease of oxygen

◆ Provision of habitat for wildlife; particularly important in city centredevelopments

◆ Reduces the environmental impactof the building within itssurroundings

The Green Roof Concept

Left: Extensive roof garden to office development. Range of rockery type plants

with wooden duckboard paving.

Centre: Semi-intensive roof garden on an industrial roof.

Lavender used as a single plant species.

INSTALLATION AND VALUE CHAINPARTNERING

Embracing the ethos of Sir John Egan’sreport Rethinking Construction, Axteractively promotes partnerships withparticipating contractors in order to deliverquality and value for money. AXTERSHIELD

Installers are fully trained in the installationof Axter materials and are chosen becauseof their workmanship quality, their integrityand their ability to complete installationswith a minimum of technical orprogramming conflicts.

AXTERSHIELD Installers will usually carry out installation of the insulation and waterproofing membranes althoughspecialist horticultural experts may complete the landscaping aspects.

GUARANTEE

Comprehensive 20 year or longerguarantees are available if the waterproofingis installed by an AXTERSHIELD Installer.These cover failure due to water ingress asa result of a latent product or installationdefect. Material warranties are alsoavailable for 10 or 15 years.

REFERENCES

Axter’s green roof systems have been usedworldwide. Recent contracts in the UKinclude:

◆ BedZED, the Beddington Zero EnergyDevelopment, Sutton, Surrey

◆ Procter and Gamble HQWeybridge, Surrey

◆ BBC White City, London◆ Paddington Basin Development, London◆ Northampton Academy◆ West One Development,

Devonshire Green, Sheffield◆ Primary School, Hadleigh, Suffolk◆ Ecology Building Society, Keighley, Yorks◆ Tong High School, Bradford◆ Riverside Quarter, Wandsworth ◆ Alibone Recycling Plant, Northampton◆ Scottish Parliament Building, Edinburgh◆ Wallsgrave Hospital, Coventry◆ Bath Street, London◆ Healthy Living Centre, Derby◆ Salmon Smokery, Bow◆ Kew Gardens

Right: Intensive roofgarden over housing.Range of both hard andsoft surfaces.

Irrespective of the type of green roof system the waterproofing and insulationrequirements are broadly similar. It isimportant to remember that the supportingstructure must be designed to resist theextra weight loading that a saturated greenroof will impose and the general principlescan be found in British Standard Code ofPractice BS 8217. The important factor is toensure that the chosen waterproofingmembranes are root resistant. Thewaterproofing and insulation specificationwill depend upon the requirement forthermal insulation; there are three choices:-

No insulation – WILOTEKT-PLUS –typically used where green roofs arerequired over underground car parks, cutand cover tunnels etc.

Warm roof – ALPAFLORE – with flat ortapered board insulation between the deckand the waterproofing, used where thethickness of the layers above the deck needsto be kept as thin as possible. However asthe waterproofing is above the insulation caremust be taken to protect the membranes frommaintenance tools etc.Inverted insulated roof – WILOTEKT-PLUS –with the insulation on top of the waterproofing.The insulation can be designed to resist theheaviest of loads and the waterproofing is wellprotected from the effects of gardenmaintenance.

WATERPROOFING

Axter’s ALPAFLORE and WILOTEKT-PLUSwaterproofing systems are perfectly adaptedto the needs of green roofs with particularresistance to impact, root action, fertilizersand insecticides.

ALPAFLORE and WILOTEKT-PLUS conform toall standards and have third partycertification.

They can be used under all forms ofinaccessible and accessible green roofs,including the use of hard surfaces on thefollowing substrates: concrete and masonry,timber and timber derivatives, profiled metal.

ALPAFLORE is normally installed as a two-layer system in its own right or as a singlelayer protection onto asphalt or over liquid-applied waterproofing systems. WILOTEKT-PLUS is ideal for use on inverted and on non-insulated roofs.

ALPAFLORE can also be used to protectunderground works such as basements.

Axter actively encourages the principles ofvalue engineering through design to ensurebest value is achieved by our clients. Throughearly design and specification participation inprojects Axter guarantees delivery of costeffective solutions to meet the most onerous ofdesign briefs and budgets thus eliminating thenecessity for expensive and time consumingvalue engineering exercises later on in thedevelopment process.

WATER MANAGEMENT

Water management is determined by whetherthe green roof is to be intensive or extensive.In some cases a hybrid system between thetwo may be required. A high proportion ofrainwater that falls on landscaped roofs isretained by the soil/reservoir system thusreducing the strain on the surface waterdrainage system. Roofs can be constructeddown to zero degree slope but provisionshould be made for internal or externalgutters, roof outlets and overflow weirs.

Roof design

For extensive roofs, where the soilthickness is a minimum, water needs to beretained and therefore a specialist reservoirboard, BAC CANALIS, is used below thegrowing medium. On slopes it is necessaryto provide a barrier to resist slippage. TheHYDROPACK trays incorporate a waterreservoir.

For intensive systems the growing mediumnormally holds moisture sufficient for plantneeds, although irrigation is oftenincorporated into the design, and drainagemust be provided to allow storm water toquickly drain. Axter provides a specialistdrainage board, AXTER DRAIN, which,whilst strong enough to withstand imposedloads, allows water to drain away freely.

HARD AND SOFT LANDSCAPING

As with all landscape gardening theopportunities are limitless. Axter works witha number of experts in their field who aimto achieve your goals. These experts willgive planting and hard standing advicebased on the building’s position, rooforientation, height of the roof above theground, roof pitch, weight limitations,preferred planting, componentsustainability, maintenance levels andperformance required from the plant andhard standing layers.

Warm extensive green roof

VERNIS ANTAC primer

VAP AL SK v.c.l.

HYTHERM insulation

HYRANGER SPOT S3V base layer

ALPAFLORE PY AR top layer

BAC CANALIS reservoir board

AXTER filter layer

Growing medium and plants

Design flexibilityto create outstandinggreen roofs

Design Requirements

Listed below are some of the items thatneed to be considered when designing agreen roof. Further information can befound in the ALPAFLORE Avis TechniqueNo. 5/02-1595 and the WILOTEKT-PLUSETA No. ETA-03/0049.

UpstandsAs in all flat roofs the waterproofingshould be taken up at least 150 mmabove the finished surface be it soil,paving, gravel etc. It is advisable to havea plant free area immediately adjacent toupstands, this can be achieved by infillingwith gravel instead.

Roof penetrationsIdeally roof penetrations, pipes, extract vents, air conditioning units, etc.,should be concentrated in one area. This simplifies the waterproofing detailsand gives greater unbroken space for plants.

FireIntensive roofs with deep soil and whichare regularly irrigated are accepted as fire resistant.

Extensive roofs are accepted as fireresistant so long as basic rules arefollowed. These include the depth andtype of soil, provision for horizontalfirebreaks, gravel strips aroundpenetrations, etc. Axter can give advicefor any particular roof design.

SafetyIntensive roofs used as amenity areas arelikely to have sufficiently high parapets tomake supplementary safety provision

With Axter’s ALPAFLORE and WILOTEKT-PLUS systems there is virtually no limit to green roof design, beit over commercial, industrial or domestic buildings, cut and cover tunnels or buried earth (underground)structures. Most landscape designs possible on the ground can be achieved on the roof so long as thesupporting structure is designed to take the load. This could be a formal garden with planted and pavedareas, an extensive roof with a wide range of rockery plants or even a replication of the uniqueenvironmental aspects of a brown field site.Axter has the expertise to turn your dreams into reality, call today for a detailed specification.

Insulated intensive green roof

WILOTEKT primer

Concrete structural deck

WILOTEKT flow control layer

WILOTEKT rubberised bitumen compound

WILOTEKT polymer bitumen membrane

AXTER XPS insulation

AXTER DRAIN

Axter filter layer

Growing medium

Intensive planting

Axter can provide a full maintenanceschedule designed for the specific needs ofeach roof. Mowing of grassed areas, removalof unwanted plants, re-planting, irrigation,fertilising, providing additional material etc.may all be required from time to time tomaintain the roof in a good vegetative state. Fire breaks and gravel areas should be kept weed free and all roof outlets should be periodically inspected and cleaned to ensure excess water can flow freely from the roof.

WILOTEKT-PLUS is a unique,second generation structuralwaterproofing system ideal foruse without screeds on concretedecks with slopes from 0° - 5°.

Awarded European TechnicalApproval No. ETA-03/0049,WILOTEKT-PLUS can be usedunder extensive and intensiveroof gardens and brown roofs.

WILOTEKT primer

Concrete structural deck

WILOTEKT flow control layer

WILOTEKT rubberised bitumen compound

WILOTEKT polymer bitumen membrane

AXTER XPS insulation

DRAINAX G

Axter filter layer

Brown roof

Insulated inverted brown roof

unnecessary. Extensive roofs are generallyinaccessible and therefore a man safesystem may be required to enablemaintenance to take place. On both typescare must be taken to ensure sufficientprovision for safety around large openingssuch as rooflights. Axter can provide arange of rooflights, access hatches,smoke and fire evacuation systemsdesigned to resist the force of peoplefalling against them.

Wind upliftCareful consideration needs to be given tothe effect of wind in the design of a greenroof. Wind uplift pressure varies from anextreme at the edge and/or corner andaround major penetrations to a minimum in the centre of the roof. In some cases itmay be necessary to provide for additionalpaving slabs or course gravel around the edge of a roof to provide sufficient wind resistance.

System loadingThe load of an intensive system is dependent on the depth of soil, types of plants, hard surfaces etc. Extensive roofs can range from 25 to 110kg/m2 depending on design.

MaintenanceIntensive roofs will require maintenance, aswould any ground level garden. Extensiveroofs whilst in general being maintenancefree do require some periodic upkeep.

Products

Description and usage of ALPAFLORE

EXCELFLOR VV ARALPAFLORE PY ARHYRANGER SPOT S3V

10 m x 1 m10 m x 1 m10 m x 1 mRoll dimensions

43 kg44 kg37 kgRoll weight

2.8 mm2.8 mm3.0 mmThickness

Mineral chippingsMineral chippingsMacro perforated film + sandSurface

SandSandPeel-off silicone filmUnder surface

CapsheetCapsheetBase layerUsage

Complementary Products

FILTER LAYERBAC CANALISAXTER DRAIN

59.8 x 38 cm114 x 105 x 0.36 cmDimensions

220 (50 m2)20Number per package

Approximately 220 kg12 kgPacket weight

100 m x 2 mRoll

41 kgRoll weight

Over AXTER DRAIN orBAC CANALIS

DRAINAX G

15 m x 2 m

19 kg

DrainageReservoir* (max 20 l/m2)DrainageUsage

Axter Limited can advise on a range of ancillary products, outlets, soil barriers, edge trims etc.*BAC CANALIS can also be used as permanent shuttering under access areas

Axter also specialises in the design and manufacture of waterproofing membranes, acousticroofing & cladding panels, continuous rooflights, domed rooflights, roof access units,smoke & fire ventilation equipment and external wall insulated cladding panels.

Further details on the above and the specifications contained in this document can be obtained from Axter Ltd.TECHNICAL INFORMATION AND SPECIFICATIONS WITHIN THIS DOCUMENT ARE A GENERAL GUIDE AND ARE SUBJECT TO CHANGE WITHOUT NOTICE. AXTER LTD DOES NOT ACCEPT RESPONSIBILITY FOR ERRORS OR FOR INFORMATION WHICH MAY BE CONSTRUED AS MISLEADING. ALL SPECIFICATIONS SHOULD BE CHECKED WITH AXTER LTD PRIOR TO THEIR USE.

Axter Limited West Rd Ransomes Europark Ipswich Suffolk IP3 9SX Tel (01473) 724056 Fax (01473) 723263Email [email protected] Web site www.axter.co.uk

For description of WILOTEKT-PLUS, see separate brochure

Printed on recycled paper using bio inks