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Conservation subdivision: clustered lots and open space

A conservation subdivision, also called a cluster or open-space subdivision, puts smaller lots on part of a tract and protects the rest as common open space. The ordinance sets how many homes the tract may hold, how much land stays open, and who owns that land.

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Quick summary: This guide explains what a conservation subdivision is, how its density works, how two North Carolina ordinances define it, and who owns the open space. It is for builders, tract buyers, and landowners who weigh a clustered layout against a conventional one. The key takeaway: clustering changes lot size and layout far more than it changes the home count, and the ordinance, not the design, sets the count.

What a conservation subdivision is

A conservation subdivision is a residential subdivision that groups homes on smaller lots and keeps a large share of the tract as permanent common open space. Ordinances also call it a cluster subdivision, an open-space subdivision, or a conservation development option.

The open space usually protects the land that is hardest to build on or most worth keeping. Examples include streams, floodplains, wetlands, steep slopes, woods, farm fields, and scenic road frontage. Lots, streets, and utilities go on the remaining ground.

State law gives local governments the authority behind these rules. A subdivision regulation may provide for the dedication or reservation of open space and recreation areas, or a payment in lieu. See N.C. Gen. Stat. § 160D-804. Each town or county then writes its own version, and the versions differ.

How density-neutral design works

Density-neutral design keeps the home count of a conventional layout and moves the homes closer together. The lots shrink, and the land saved becomes common open space.

The yield plan. Many ordinances start from the number of homes the base zoning allows on the tract. That number does not grow because the lots are smaller.

The trade. Each square foot taken off a lot goes into open space. Durham’s cluster rule states it directly: lot area reductions are matched by equal amounts of common open space on a one-to-one basis.

The exception. Some ordinances add density as an incentive, so the option is not always neutral. Read the density line of the option, not only its open space line.

How two North Carolina ordinances define it

Raleigh and Durham each write the option into their unified development ordinances, with different numbers.

Raleigh: the conservation development option

Raleigh’s housing options section says a conservation development “trades smaller lot sizes (with reduced setbacks) and additional density in exchange for preserving common open space.” The applicant sets aside 40 percent of the project area, or the district’s minimum acreage if that is greater, as common open space. A project below the district minimum can use only the conventional option.

Article 2.4 sets the district standards. The open space must be 60 percent contiguous and at least 50 feet wide. A set share of lots must abut it, from 30 to 60 percent by district.

Durham: cluster and conservation subdivisions

Durham has two forms. A cluster subdivision needs a site of at least two acres. Its density may not exceed the base district’s maximum. A cluster townhouse project keeps at least 20 percent of the gross area as open space.

A conservation subdivision in the Residential Rural district is allowed by right, subject to subdivision approval. It keeps 50 percent of the tract’s gross area as open space. Its density is the gross area times the district’s maximum gross density, and that gross area includes land the ordinance usually excludes from the density count. The applicant brings a site analysis map to the pre-application conference. It shows streams, wetlands, contours at no more than 10-foot intervals, and soils that can take on-site wastewater.

Watch for: An option that sounds the same in two towns can produce a different lot count. Read the density line, the open space percentage, and the minimum site size in the ordinance that governs the tract.

Who owns the open space

The open space is not part of any private lot. A homeowners association, a land trust, or a public body owns it, and a recorded instrument keeps it open.

  • Raleigh. Sec. 2.5.7 allows a land conservancy, a land trust, or a homeowners association with lien authority to own it. Title passes in fee simple no later than the sale of the first lot in that phase. If the association dissolves, the open space may be offered to another entity, and then to the city.
  • Durham. Sec. 7.2.5 requires a recorded instrument that protects the open space in perpetuity. Options include a permanent conservation easement held by a land trust or a governmental entity, and dedication to a homeowners association that accepts permanent maintenance. A maintenance program is due before final plat approval.

A recorded conservation easement binds every later owner of the open space. See Conservation easement: what it means for land buyers.

The association model has a cost that outlasts the sale. Dues fund mowing, trails, stormwater ponds in the open space, and insurance. A buyer of the finished lots inherits that budget.

What it does to lot count and lot size

A conservation layout changes lot size first and lot count second. Under a density-neutral rule, the count stays at the base district number, and each lot gets smaller.

Raleigh shows the size change in its tables. In the R-4 district, a conventional detached lot needs 10,000 square feet, per Sec. 2.2.1. Under the conservation option, the same district allows 6,000 square feet, per Article 2.4. In R-1, the maximum density rises from 1 unit per acre to 2.

Lot count can still fall below the base number. Wetlands, buffers, slopes, stormwater measures, and septic areas take ground in any layout. A tract that cannot fit the base count on its developable ground will not fit it by clustering. See Minimum lot size: what it is and how to find it and How many houses fit on an acre.

Clustering can also cut cost. Shorter streets and shorter utility runs serve the same number of homes. Durham’s cluster purpose statement names that aim: a more efficient layout of lots, streets, and utilities.

Take action: Ask planning staff which subdivision options the tract’s district allows and how each one counts density. Start with How many lots is this tract, really?

When the option fits a tract

A conservation layout fits best when a large part of the tract is hard to build on and the rest is good ground. Examples include a farm with a creek corridor, a wooded tract with steep side slopes, or a parcel with a floodplain along one edge. The protected land becomes the required open space, and the homes go where the ground is best.

Wastewater decides many rural cluster designs. A small lot may not hold its own septic field, so the plan can need public sewer, a community system, or drainfields in the open space where the rules allow. See Sewer, septic, or a package plant.

Start the test with the record. Floodplain maps, soil surveys, and stream data show where the developable ground is. See Gross acres are not usable acres. Then a licensed land surveyor, a professional engineer, and planning staff turn the option into a plat.

Key recap

  • A conservation subdivision groups homes on smaller lots and keeps a large share of the tract as common open space.
  • State law lets local subdivision rules require open space. Each town or county sets its own option and numbers.
  • Raleigh sets aside 40 percent or a district minimum. Durham’s rural conservation subdivision keeps 50 percent of the gross area.
  • Durham caps cluster density at the base district maximum. Raleigh’s option can add density in some districts.
  • An owners association, a land trust, or a public body owns the open space under a recorded instrument.
  • Clustering changes lot size more than lot count. Wastewater and stormwater still decide what fits.

Questions

Does a conservation subdivision allow more homes?

Sometimes. A density-neutral rule, such as Durham’s cluster rule, keeps the base district count. Other ordinances add density as an incentive, such as Raleigh’s R-1 option. Read the density line of the option in the ordinance that governs the tract.

Who maintains the open space in a cluster subdivision?

The owner of the open space maintains it, usually a homeowners association funded by lot owners’ dues. A land trust or public body can own it instead where the ordinance allows. The recorded plat and declaration name the owner.

Is a conservation subdivision the same as a conservation easement?

No. A conservation subdivision is a layout option in the zoning or subdivision rules. A conservation easement is a recorded legal restriction on land, and some ordinances use one to protect the open space in a conservation subdivision.

References

Primary sources cited on this page, in APA style.

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