Open Space Residential Design (OSRD), also known as conservation subdivision design, is a method of planning residential subdivisions to maximize the amount of preserved open space and protect natural and cultural resources without reducing the number of homes constructed. OSRD is an alternative to conventional subdivision design under existing zoning bylaws, which often mandate a minimum lot size of one acre or more. Even when lot sizes exceed one acre, sprawling lawns, driveways, and other developed surfaces may reduce the integrity of open spaces and natural resource areas.

OSRD involves a four-step planning process:

  • Designate open spaces, including “primary conservation areas” such as wetlands and floodplains under regulatory jurisdiction and “secondary conservation areas” with other ecological resources worth protecting, such as steep slopes, mature woodlands, prime farmland, and meadows. The remainder is the buildable area.
  • Locate house sites within the buildable area.
  • Locate roads and trails to ensure connectivity and access to open spaces.
  • Draw lot lines for individual house lots

Municipalities can adopt OSRD bylaws to enable and promote the OSRD process for site design. The bylaw may be structured to allow OSRD “by-right” or even to require the use of OSRD on developments larger than a minimum size or located in sensitive areas such as aquifer recharge zones. Alternatively, the bylaw may allow OSRD by special permit from the Planning Board, as an exception to conventional zoning. By-right OSRD is generally preferable because it gives OSRD parity with conventional zoning, requiring no more burdensome permitting requirements. However, some municipalities prefer the discretion afforded to the Planning Board under a special permit process.

Local Examples

In the Ipswich River watershed, Hamilton, Beverly, and Wilmington have passed OSRD bylaws, and Ipswich has refined a similar cluster bylaw that includes OSRD principles. Ipswich allows clustered subdivisions by special permit, which gives the Planning Board wide latitude to protect community and ecological interests. On the other hand, Wilmington requires new subdivisions on more than 20 acres to use an OSRD approach rather than conventional design.

In 2006, Beverly adopted mandatory by-right OSRD for developments of four homes or more. While Beverly has had a cluster provision in its zoning ordinance for 16 years, it has only been used once since it required special approval from the Zoning Board of Appeals. The by-right OSRD bylaw substantially streamlines the process and makes OSRD the default method of subdivision design.

The development of Partridgeberry Place, a new subdivision near Hood Pond in Ipswich, illustrates the benefits of OSRD. The site originally consisted of 37 acres of forest and forested wetland. After following the four-step OSRD process, 30 acres were set aside as permanent open space, the majority of which was transferred to the Massachusetts Department of Conservation and Recreation state forest system. Twenty lots were then sited in the remaining buildable area.


Green Neighborhoods, Open Space Residential Design in Massachusetts (html)

OSRD Model Site Plan Bylaw (By-Right) (pdf)

OSRD Model Bylaw – Special Permit (pdf)

Massachusetts Executive Office of Environmental Affairs, Smart Growth Toolkit (pdf)

Metropolitan Area Planning Council, The Conservation Subdivision Design Project: Booklet for Developing a Local Bylaw, 2000 (pdf)

Purinton, Tim. Open Space Residential Design: A Community Choice, presentation at Ipswich River Restoration Conference, November 2000 (pdf)

Water Wise Communities: Index

  1. Master plan for smart growth
  2. Integrated water resources management plan
  3. Comprehensive open space plan
  4. Water use restriction bylaw
  5. Outdoor water use bylaw
  6. Private well bylaw
  7. Stormwater management program and bylaws
  8. Open space residential design bylaw
  9. Source water protection program and bylaw
  10. Non-zoning wetlands bylaw
  11. Conservation water rate structure
  12. Water bank or offset program
  13. Stormwater fee or utility
  14. Rebate program
  15. Dedicated funding source for land acquisition
  16. Water audits and leak detection
  17. LID demonstration projects on municipal property
  18. Habitat restoration on municipal property
  19. Outreach program
  20. Water conservation coordinator