Green Roof Design

HYDROPACK green roof being installed on STM in Quebec, Canada

 

Vegetal i.D.. 's expert team is dedicated to the success of its green roofs and is always available to help the architect or landscape architect in the design process. To create a green roof, it is important to take into consideration two types of factors:

The Environment of the Project:

  • The location will specify the hardiness zone that the project is in and this will guide the plant selection. Contact an expert at Vegetal i.D. to discuss the best plants available for your region.
  • The building configuration will be taken into account to design the vegetation free zones and select the appropriate plants according to sun exposure.
  • The wind load requirements will be an important factor to select the best method to attach the system. It will also be a factor in determining the appropriate width of the vegetation zone and the design of the parapets.
  • The design intent of the client is always essential. Does the client want a natural look or a sophisticated design? Is the roof accessible to the public or highly visible? These factors will help us guide you to create a low maintenance green roof, a high-end landscape design, or a roof focused on stormwater management to fit the needs of the client.

The Characteristics of the Roof Itself:

  • The waterproofing membrane assembly must be compatible with the green roof system.
  • The slope of the roof will determine the type of attachment system.
  • The maximum load capacity of the structure will guide your choice of green roof systems.
  • Designing access to irrigation is essential, even if a permanent irrigation system is not planned. During periods of extreme heat and drought, it is better to be able to water the plants, rather than replace them.

Quick Design Tips

  • Adjacent windows or walls reflect sunlight onto the roof and, in some situations, kill vegetation. Design wider vegetation-free zones in these areas.
  • In shade environments, use shade tolerant plants
  • Do not place vegetation underneath runoff discharges from adjacent roofs
  • Avoid installing a green roof underneath trees
  • Always design water access to the roof

Vegetal i.D.'s Options Related to Design Intents

Design Intents Vegetal i.D. Solution
City Code
Hydropack Standard Mix
LEED
Hydropack Accent Mix - Natives
Stormwater Management
Heat Island Reduction
Hydropack Accent Mix - Grasses
Landscape Designs
Hydropack Custom or Accent Mix
Accessible Green Roof
Hydropack Custom or Accent Mix
Biodiversity
Hydropack any solution

 

Vegetation Free Zones

The vegetation-free zone is a band that extends around the roof and any structures protruding from the roof that is 20-36 inches wide. (Note that there is no need to install dividers between planted areas and vegetation free zones when installing Hydropack® modules).

Vegetation-free zone with river rocks
Vegetation-free zone without dividers

The goal of designing vegetation free zone is to:

  • Facilitate inspection of flashing and runoff drainage
  • Enable water to flow easily to the runoff drains

 

The vegetation-free zone may be protected with:

  • Stone ballast 1-1/2'' diameter stone ballast (38 mm)
  • Precast slabs laid on the drainage layer or on studs
  • Prefabricated timber decking laid on studs
  • Self-protected waterproofing membrane (suitable for all roof pitches) if permitted by the technical specifications.
  • The same root barrier should be used in the vegetation free zone as in the planted area.

Vegetation free zones are not considered to be accessible areas and should not be used as pathways by rooftop equipment maintenance personnel.

Concept Diagrams (click to enlarge)

profile vegetation free zone vegetation free zone diagram

Parapets and Wind Protection

A parapet is often built to decrease the roof's exposure to wind. For guidance, use ANSI- SPRI RP-14, Hydropack® is considered to be a # 4 ballast.

Building Height
Parapet Height
(Above growing media)
Vegetation Free
Zone Width
Less than 150'
(46 m)
6" (150 mm)
20" (0.5 m)
More than 150'
(46 m)
30" (750 mm)
36" (0.9 m)
In order to decrease wind exposure on the green roof, a 4" high metal edge along the perimeter of the green roof is recommended to protect the modules. For winds faster than 90 mph, we recommend reinforcing the tray attachments with UV resistant zip ties.

 

 

 

 

 

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As an expert in green roofs, Vegetal i.D. is a member of:

adivet association des toitures végétales   GRHC-white-no-background-copy-smaller Milwaukee Water Council AIA-provider-logo

US Green Building CouncilPole Dream, Pole de compétitivité eaux et milieux - région CentreGreenroofsGTTV Conseil GTTV 

Looking for a product to achieve a successful green roof or achieve your on-site stormwater management goals? As experts in green roof and stormwater management products, Vegetal i.D. is a manufacturer and provider of green roof and stormwater management solutions.  Vegetal i.D. stays with every project from concept to installation so with Vegetal i.D. your never on your own.

Vegetal i.D. offers modular extensive green roof products such as Hydropack®, stormwater management solutions and green roof solutions for any pitch using Acropack.