District of Columbia Green Area Ratio - Zoning Regulations
The District of Columbia (Washington D.C.) Green Area Ratio (GAR) is an environmental sustainability zoning regulation which sets requirements for landscape elements and site design to help reduce stormwater runoff, improve air quality, and mitigate urban heat. The GAR sets minimum lot coverage standards for landscape and site design features to promote greater livability, ecological function, and climate adaptation in the urban environment. The GAR requirements provide a firm retention target and allow local governments to weight the elements they prefer in order to influence behavior, while providing some measure of flexibility for property owners.
The GAR score relates to an increase in the quantity and quality of environmental performance of the urban landscape. The GAR assigns a weighted score to a building based on the types of landscape and site design features that are implemented and the amount of area they cover. This score is based on an assessment of the square footage of landscape elements that can be incorporated with each type of land use.
The Green Area Ratio is the ratio of the weighted value of sustainable landscape elements to land area. Landscape elements included are in 13 approved categories: soils and amendments, bio-retention, new and existing plantings, tree preservation, vegetated walls, vegetated roofs, permeable paving, enhanced tree soil systems, renewable energy, water features, native plants, food cultivation, and harvested stormwater irrigation.
GAR applicants also must provide a landscape maintenance plan prepared and signed by a Certified Landscape Expert that describes how the plantings, water features and hardscape features will be cared for and maintained including:
- Soil preparation;
- Use of compost;
- Plant replacement;
- Weed and pest control; and
- Control of noxious or invasive species.
As explained by the DDOE, the Green Area Ratio is a zoning regulation administered by the Department of Consumer and Regulatory Affairs (DCRA), District Department of the Environment (DDOE), and District of Columbia Office of Zoning. Plans are submitted to DCRA for zoning approval. If the GAR applies, DDOE reviews and approves GAR plans as part of the building permit application. The applicant’s Certified Landscape Expert signs off on GAR plans and confirms appropriate installation or preservation of landscape elements during construction. After construction, the DDOE inspector and the Certified Landscape Expert jointly review the installation for conformance with the approved plans. After DDOE signs off, the Zoning Administrator can then grant the Certificate of Occupancy.
For more information, DDOE offers the GAR Guidebook:
The GAR Guidebook provides direction in the following areas:
• Additional details on specific zoning language
• Plan submission guidelines
• Scoring requirements and worksheets
• Descriptions of landscape and building elements eligible for scoring credit
• Certified Landscape Expert’s responsibilities for design, construction, and maintenance
• Property owner’s responsibilities for maintenance of landscape elements
Publication Date: October 1, 2013
- District Department of Energy and the Environment (DDOE) - Washington DC
- Green Infrastructure Toolkit > Scaling Up: Integrating Green Infrastructure into Existing Processes > Regulatory Tools