Cluster housing groups homes together on fairly small lots near one another, with larger open spaces in the same development left untouched.
The benefits of this development pattern are two-fold:
(1) The contiguous open spaces are good practice either for conservation and wildlife habitat purposes, or for agriculture, while
(2) Placing the homes near one another minimizes the cost of running roads and utilities to them, and allows for convenient socializing and a real sense of community.
As our photo shows, this isn't some crazy new-fangled scheme dreamed up by urban planners. Mountain and lake villages, as well as many other historic small towns where people basically farmed the outskirts of town, are the prototypes for this contemporary development that often has nothing to do with agriculture.
In places that practice land use zoning, sometimes the cluster development is able to take advantage of an existing planned unit development district. The PUD, as it is often called, allows more flexibility in lot size and placement than typical zoning districts.
Despite our headline, cluster housing or a conservation subdivision also is appropriate in a suburb or even large city where one large land parcel has remained undeveloped.
If you have such properties, but you'd like to save as much recreational space or conservation land as possible, consider offering an incentive for cluster housing.
Generally zoning ordinances require minimum lot areas, road frontage, and setbacks from the street and property lines, as well as a maximum height, percentage of the lot that may be covered with buildings or other impermeable surfaces, and so forth.
This results in a subdivision with large lawns. If diversity of wildlife is one of the goals, these large turf grass areas are a poor substitute for a wilderness of the type native to your area.
In semi-rural situations, where the the cluster housing concept is most popular, these ranchette style lots of three, five, or ten acres each often result in septic tank systems.
However, if the geology and climate of the area are conducive to an urban type of sewer system that can be managed by some adjoining municipality, that is usually far preferable.
Both individual septic systems and the small "package" sewer systems sold for subdivisions in some parts of the world need regular maintenance and someone who understands how they work.
In the typical cluster housing development or conservation subdivision, lots are sold individually, with a homeowners association managing the conservation land as common ground.
If the purpose of the cluster housing is conservation, I also know of some instances in which the association pays a nominal fee to an interested non-profit organization to manage the conservation land.
In yet other situations, some or all of the households earn at least part of their incomes from agriculture, and the purpose of the cluster subdivision is to provide neighbors and playmates for the children. Yet building and maintaining a quality road isn't as expensive as it would be if the houses were dispersed over individual farms.
By the way, it's possible to have a cluster housing development where all the land in the development is included within an individual lot too. You just wouldn't have conventionally shaped rectangular lots. The lots would have a very narrow frontage along the main road or an access road for the subdivision, and then become much larger in the rear, shaped like a wedge of pie.
There are several advantages to clustering the residences into one or possibly two or three parts of the subdivision:
• Development expense will be lower, and therefore housing affordability will improve.
• The open space performs more valuable environmental functions if it is contiguous, including better absorption of air pollution, greater filtering of rain water, and more uptake of greenhouse gas emissions.
Connected open space provides habitat for larger animals and a greater variety of animal and plant life than would be seen in the same amount of open space parceled out into individual yards.
Groundwater recharge of the aquifer is more effective, because rain runs off much more slowly in woodlands, prairies, and other natural environments than from rooftops, patios, and barns. Slowing down stormwater runoff also is a form of flood prevention.
• Joint community facilities can be developed. Examples might be a fishing lake, a vegetable garden, a swimming pool, an implement storage shed, or a barn.
• Sometimes the motivation for keeping a large percentage of an overall development parcel in a contiguous non-developed area would be recreational. Maybe you’re in a hunting-oriented community or have an unusual geological feature or spring you’d like to preserve and feature. Maybe you want trails through the woods.
If your area does not have zoning, or if by state law agricultural land is exempt from zoning, you may encourage cluster housing simply by presenting workshops on the topic.
Also if you have any road-building or utility ownership powers, those can be used to encourage or give incentives for cluster development as opposed to more linear patterns.
In areas with zoning, sometimes the first step for a developer or an interested government would be to see that a planned development zoning classification is applied to the area or areas where cluster subdivisions would be appropriate.
A developer then must submit a detailed site plan, and those details are approved as part of granting the zoning classification. In a well-drafted ordinance, criteria for approval of the PUD or PD are listed, but still there is an element of subjectivity and judgment involved in what will be approved.
However, we think it's a better idea to write a separate cluster housing zoning district regulation, especially if your aim is to promote conservation and to inhibit suburban sprawl.
This separate district regulation would give the town council more specific criteria related to conservation or recreation.
For example, you might require that 75% of the site remain undeveloped, meaning there would not be buildings, driveways, patios, decks, or cultivated lawn areas in that preserved area.
Maybe that's too much; maybe 50% would be a big step forward in
your environment. That area essentially will become common ground, so
you will want to have standards for requiring a homeowner’s association.
If you want to retain some minimum lot sizes, you may do so. Some frontage on a public road, at least enough for a driveway, would be highly desirable. Often two to four houses have a sort of shared semi-circular driveway off the main road that serves as their primary access, with only a short additional driveway back to individual garages.
You can have minimum setbacks from property lines for various types of buildings also.
You can have sign regulation, parking minimums or maximums, or anything else normally regulated within a zoning ordinance.
The key ingredient really is that minimum percentage of the land that must be left in open space.
As a governing body, you may leave that open to the applicant to propose, rather than setting that percentage in advance.
In reality some areas will provide a superior quality of forest to be preserved, while others may offer only scrubby vegetation that has been ruined in part by plant species not native to your area (sometimes called "exotic" or "invasive" species).
So if you require 50% of the land to be reserved for conservation purposes in all instances, your community will receive considerably more environmental benefit from the quality forest from the poor-quality hodge-podge of vegetation.
You'll need to establish a minimum acreage for the entire cluster housing development. I'd think that number would be at least 10 acres, and maybe considerably higher if you're encouraging or preserving agriculture.
Establish a list of permitted uses in a proposed cluster zoning district. I wouldn't leave that to chance. You may want to allow simply single-family residential and agricultural accessory uses, or multi-family or two-family might fit into your game plan as well.
Occasionally a development of this type is so large that you need a tiny neighborhood commercial district, but don't permit that "as of right."
For an even broader framework of green ordinances and plan review ideas, see this site on green planning.
We've talked about a lot of possibilities, but to encourage cluster housing, here are some recommendations:
1. If you have zoning, create a separate zoning classification for cluster development, instead of lumping them in with planned unit developments. In this way, your criteria can be more specific and objective.
2. If you wish, go ahead and map some parcels of land for this zoning classification. The advantage is that you can select the land you most wish to preserve for habitat conservation, and thereby get around the issue of only poor quality habitat being "preserved."
3. Of course, rezoning applications to allow cluster housing also should be permitted.
4. Investigate your subdivision regulations to make sure that common configurations seen in conservation subdivisions would be allowed under the subdivision regulation. Often that might not be the case, so a revision of your subdivision regulation could be required in tandem with the zoning ordinance as well.
5. Your county or village attorney will need to be involved in these discussions to make sure that nothing you are doing will preclude easy sale of the lots within a cluster development.
6. If you do not have zoning, it's still desirable to talk informally with developers, property owners who are selling, or rural families about the desirable characteristics of cluster housing.
For a very detailed report on the status of cluster zoning, flexible zoning, and open space residential design in Massachusetts, see the Pioneer Institute report.
This would be helpful to most of you.