Open Space Ratio
When talking about the open space ratio we are referring to a term that is used in zoning laws and regulations. The open space ratio is a term used to measure open space on a developed land or zoning lot. The open space ratio is calculated in the percentage of open space in the building's square footage. For example, a housing subdivision containing 100 acres has devoted 10 acres to open space. Therefore, the open space ratio is 1/10 or 10 percent (10/100). Or an office building of 10,000 square feet with an open space ratio of 20% will have 2,000 square feet designated to remain open space.
Open Space Ratio in Residential Real Estate
The term open space ratio is a concept that applies to residential developments, and it usually refers to commonly used open space. While not necessarily a way to determine the ratio of “green” open space on lots of land proposed for residential development. The term open space ratio can refer to two types of open space:
- Allowable Areas
Allowable open space are the areas that are required common areas to be maintained and remain undeveloped for the benefit of those living or working on the lot parcel: parking lots, yard requirements, floodplains, recreational areas, stormwater management systems, etc.
- Prohibited Areas
Prohibited open space areas are privately owned sites that are not accessible for those living or working on the lot parcel and that are also available for further structural developments.
How is Open Space Ratio Calculated?
The open space ratio is a zoning law used by municipalities to be able to control the types of buildings built, their height, and their ratio of open space. It is a means for municipalities to ensure that the open space available on a developed land makes up a certain percentage of the lot developed. In most cases, that requirement is of a 20% open space ratio.
Open Space Ratio Formula:
Open Space Ratio (OSR) = Commonly-owned Open Space / Total Area Proposed for Development
So if you have 12 acres available for residential development and you have 6 acres of commonly-owned open space (ponds, recreation area, parking area, buffers, etc) you will have an open space ratio of 50%.
Popular Real Estate Terms
Relating to trees or shrubs normally found in temperate climates. Deciduous trees shed their leaves in the fall. Deciduous woods such as pine, oak, Maple, redwood, and spruce are widely ...
Also called accounting or unadjusted rate of return. The return computed by dividing the anticipated future annual net income by the required investment in real estate. Sometimes the ...
Lender's written statement and accounting for the remaining balance, date of maturity, and interest rate on a mortgage. The lender is certifying this information to the borrower or any ...
Recognizes profit on a long-term construction contract as it is earned gradually during the construction period. This approach is preferred over the completed contract method because it ...
After-tax cash flow is a calculation method for companies’ financial performance to show their ability to generate cash flow through their operations. The after-tax cash flow formula ...
Provision in a mortgage that requires the final payment to be substantially more than all other payments. ...
Bond collaterized by real assets. Two kinds of mortgage bond are senior mortgages and junior mortgages. A mortgage bond may have a closed-end provision that prevents the firm from issuing ...
The central core of an urban area. The inner city contains the major commercial center, termed the central business district (CBD). Close to the inner city are also some of the poorest ...
Ownership of property by two or more people in undivided interests, without the right of survivorship. Each coowner's interest may be conveyed separately by its owner. Tenancy in common ...

Have a question or comment?
We're here to help.