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Green roof design involves the use of plants and vegetation to create a layer of living greenery on the roof of a building. These green roofs can provide a number of benefits, including reducing the urban heat island effect, improving air quality, and providing natural insulation to the building.

Green roof design includes the following.

  • Understanding the structural stability and load bearing capacity (dead and imposed loads) of roof. The structural loading is a combination of dead loads, all permanently placed parts of the roof, including hardscape, plants, growing medium, features, etc; and the imposed loads, such as people and temporary components.
  • Waterproofing of the structure and the green areas.
  • Arrangement of surface and subsurface drainage of the roof.
  • Soil fill, and planting with limited root zone.
  • Location and planting of trees.
  • Location and design of pavements, walls, landscape features and structures.

1) Design Guidelines


The guidelines given below shall be followed for the design of green roofs (see Figure above).


  • A concrete layer shall be laid on the roof slab to provide slopes for subsurface drainage of vegetated areas, drains.
  • Where there  is  a  large  green  area  on  the  roof, perforated pipes laid in screed shall be used to channelize subsurface water to the adjoining drainage chambers.

Waterproofing membrane

  • A protective layer shall be laid on the sloped concrete surface to protect the building’s structure and the waterproofing membrane on the building slab.


  • Drainage shall comprise of surface drainage and subsurface drainage.
  • Subsurface drainage layer shall be very porous to permit water to pass easily through it.
  • It should be permanent and continuous over the entire roof surface and strong enough to support the weight of the plant materials and hardscape above it.
  • This layer shall be kept free of any materials that could prevent the free flow of water to the drains.
  • Drainage cells may be used to increase soil depth.
  • Surface drainage shall allow for easy flow of water from the roof surface to the drainage chambers on grade.
  • It shall comprise of drains, catch basins.
  • They shall be carefully designed to avoid expansion joints on the roof.

Filter membrane

  • Helps in containing the roots and the growing medium, while allowing for water penetration and prevents clogging of the drainage layer and roof drains.


  • The depth of soil shall depend on type of planting, screed thickness and structural allowance for fill above slab.


  • Shall be grass, shrubs, ground covers, trees. 
  • Type of vegetation shall depend on the structural allowance for fill above slab.


  • Shall be adequately provided.
  • The thin depth and well-drained soil used in green roof construction cannot provide the plantings with the subsurface water normally available to ground level plantings.
  • Care shall be exercised to prevent the soil mass from drying out and causing damage to the plant materials.


  • As described in by the Consultant shall be integrated with the landscape


  • Includes paving, street furniture and water features, walls, fences, screens, pergolas,  kerbs, fire paths, roads.
  • The landscape elements shall be considered in relationship to the structural limitations of the roof and its supports below.
  • The street furniture, including lighting fixtures shall be carefully anchored on rooftops.

2) Green roof system

  • Green roofs have the potential to improve the thermal performance of a roofing system through shading, insulation, evapotranspiration and thermal mass, thus reducing energy demand of building for space conditioning.
  • The green roof moderates the heat flow through the roofing system and helps in reducing the temperature fluctuations due to changing outside environment.
  • If widely used, green roofs can reduce the problem of heat island effect which in turn reduces the energy consumption in urban areas.
  • Green roof systems comprise a lightweight growing medium, plants and a root repellent layer in addition to the regular components of a roof.
  • The additional components and thickness of the growing medium provides thermal insulation, while the green cover lowers ambient temperatures through evapotranspiration.
  • Issues related to dead weight and water proofing should be considered while designing roof.
  • There are three types of green roofs, as follows.

Intensive green roof

  • It is like a conventional garden or park with almost no limit on the type of available plants including trees and shrubs.

Extensive green roof

  • It is designed for little maintenance or human intervention once it is established.

Modular block green roof

  • It is designed in modular units which inter-lock and each module contains drainage systems and plants.
  • Use of photovoltaic panels for renewable energy can also be advantageously used for their effect on shading of roof top.

Overall, green roof design requires careful consideration of a variety of factors to ensure that the green roof provides maximum benefits while also being safe and sustainable.

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