INSTALLING & 

MAINTAINING GREEN ROOFS

Installing a green roof is a great undertaking. This page is not intended to be a comprehensive green roof installation or maintenance manual. It is strongly advised to have a professional design-build consultant guide you through the design process, assist with procuring funding and permits, and safely install and maintain your green roof.

Before Installing a Green Roof

Consider

Location

The height of the green roof, its exposure to wind, its orientation to the sun, and shading by surrounding buildings during all parts of the day. The area’s general climate and microclimate on the roof must also be considered.


Structure

Before adding a green roof, a structural engineer will need to analyze the building’s current weight-bearing capacity to determine if the roof can support a green roof system or if additional reinforcement is required. Also consider the size, slope, height and directional orientation of the roof.

 

Loading guide (saturated weights)
Extensive green roof: 12 to 30 lb/sqft
Intensive green roof: 40 to 102 lb/sqft

Project Goals & Intended Use

Identify the reasons for installing a green roof

 

  • Aesthetics and access for tenants or the general public

  • Food production

  • Wildlife habitat

  • Stormwater management

  • Minimizing building energy usage

  • Sound absorption

  • Green building certification or policy requirement

  • General access to the roof for installation and maintenance

Green Roof Installation Checklist

  • Determine project budget

  • Assemble a design team

  • Establish design, installation, and maintenance goals

  • Conduct life cycle cost analysis

  • Determine the project timeline

  • Determine available green roof financial incentives

  • Conduct a site analysis

  • Determine the type of green roof desired based on goals and budget

  • Design green roof

  • Install bird-friendly glass elements

  • Create a maintenance plan

Green Roof Installation FAQ

How much does it cost to install a green roof and are funding options available?


The average cost to install a green roof ranges from $10 to $12.50/sqft for an extensive (Sedum) green roof and $16 to $20/sqft for more intensive green roofs. If the green roof is integrated into the design in the beginning of the construction, the costs per square foot decreases.




What is the difference between an intensive and extensive green roof?


Extensive Roof

  • Shallow growing medium (soil) between 2 and 6 inches
  • Less structural support
  • Limited plant diversity with less intricate root systems
  • Less investment and little maintenance once established
  • Requires minimal maintenance after the first year
  • For roofs without occupancy or capacity for gathering
Intensive Roof
  • 6+ inches or deeper growing medium (soil)
  • More structural support as growing medium to support heavier plants
  • Can support a larger variety of plants and trees
  • Can support raised beds
  • Higher initial investment and more intensive maintenance
  • May require an irrigation system
  • May be accessible for residents to socialize, with appropriate access and Certificate of Occupancy




Can I install a green roof myself or should I hire a professional?


In NYC, it is advised to connect with a professional design-build firm consultant who can guide you through the design process, assist with procuring funding and permits, and safely install and maintain your green roof. Scroll below to see design-build firm examples.




What time of year is best to install a green roof in NYC?


Spring. Planting in high summer will require extra irrigation and autumn may not allow enough time for the plants to get established before winter. Some plants can be installed while dormant in the winter.




How long does it take to install a green roof?


Residential projects can be installed within a few days. Commercial installations can take up to two weeks due to generally larger roof sizes. Allow time for permitting and filing processes that may apply to your project.




How long does it take for plants to be established on green roofs?


It can take plants a minimum of three years to establish on green roofs.




Do all green roofs need irrigation?


Extensive green roofs may not require irrigation because most suitable plants are drought-tolerant. Depending on the plants selected, intensive roofs may require drip irrigation.





GREEN

ROOF

MAINTENANCE

Maintenance is critical to a green roof’s long-term success. It includes watering, weeding, harvesting, and checking for eroded growth medium (soil). During its first two years, the establishment period, a green roof requires more intensive care.

Green Roof Maintenance FAQ

How much time and labor is required for maintenance?


Intensive systems typically require more maintenance than extensive systems because they have a greater diversity of plants with different care requirements, and typically need irrigation. Extensive green roofs may require plant maintenance twice a year to check for weeds or damage. Intensive green roofs may require weekly visits for irrigation, pruning, and replanting.




How much does it cost to maintain a green roof?


The average maintenance cost for extensive green roofs ranges from $.75 to $2/sqft, while that of intensive green roofs ranges from $1.25 to $2/sqft. The cost of roofs with landscape design will be higher. Annual maintenance of green roofs costs 21 cents to 31 cents more per square foot a year than maintenance of a black roof. The overall green roof maintenance costs decrease after the first two years.




How are green roofs maintained in the winter?


Plant a cover crop, or cover the roof with burlap or another material that reduces erosion and protect plants. This may not be necessary for all green roofs and depends on the specific plants used.




How often does a green roof need to be watered?


Extensive green roofs need very little water because most plants are drought-tolerant. It is recommended to install installation on intensive green roofs either above or below the growing medium.




How are pests controlled on green roofs?


Do not use herbicides, pesticides, or any other chemicals that could negatively affect the roofing membrane or warranty. Natural pest controls, such as ladybugs, are required.




Do green roofs need to be fertilized?


Green roofs may need periodic fertilization. If fertilizing a green roof, use slow-release, organic fertilizer in the spring.





Example Design Build Consultants

Example Material Distributers

Additional Resources

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Website Developer: Stephanie Kale

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The Green Roof Researchers Alliance is funded by The New York Community Trust, A.P.J. O’Connor Fund, and the LuEsther T. Mertz Fund