INSTALLATION & MAINTENANCE
Climate and microclimate (roof height, sun and wind exposure, and average precipitation)
Roof slope, the age of the waterproofing membrane, and building HVAC systems
Structural capacity, including dead load and live load
Accessibility for ongoing maintenance and egress
Rainwater harvesting and drain locations
A water source for irrigation and a power source for installation or lighting, if needed.
City sustainability requirements, building codes, and insurance requirements
Growing zones: NYC is growing zone 7, but green roofs may be closer to a zone 5 depending on wind and exposure
When designing a green roof, it is important to consider the environment, intent, and building requirements.
The information below can help you get started, but it is not intended to be comprehensive green roof installation or maintenance manual. It is strongly advised to hire a professional design-build firm consultant to guide you through the design process, assist with procuring funding and permits, and safely install and maintain your green roof. Assess the following elements to help determine the roof’s design.
Before Installing a Green Roof
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.
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
Aesthetics and access for tenants or the general public
Minimizing building energy usage
Green building certification or policy requirement
General access to the roof for installation and maintenance
Green Roof Installation Checklist
Determine project budget
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
Create a maintenance plan
Installation common questions
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?
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
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.
NYC Design-build consultants
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.
Maintenance common questions
How much time and labor is required for maintenance?
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?
How often does a green roof need to be watered?
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.
Fertilizers have the potential to make your crops extremely productive
but at a cost. Synthetic fertilizers are costly and also emit greenhouse gases during production and contribute to runoff into waterways. Alternatives to
synthetic fertilizer apply the compost that you make at home from food waste directly onto your soil or "compost tea."
Some crops are more nutrient heavy than others. It is important to rotate where you grow your crops every growing season to keep the nutrients in your soil diverse. In between planting season, crop covers can replenish the soil of nutrients and protect soil from erosion.
Chemical pesticides can damage your soil as the chemicals can
harm the microbiota community that keeps your soil in tip-top shape!
It is important to combat pests, and a great natural pesticide can
include ladybugs, spiders, and other carnivorous insects.
Tilling your soil can make the planting season easier but depending on the depth can cause soil erosion. Tilling damages the soil structure, breaks up
established microbiota communities, and causes compaction
to your soil, making it harder for crops to establish roots. In-between planting season, plant a cover crop.