In Small Towns and Rural Areas,
Try Cluster Housing

Cluster housing is a technique allowing flexible zoning to group residences together allowing for more open space preservation than might otherwise be permitted. It is a variation on the planned unit development concept, and often it is particularly applicable to rural development or small towns.

Despite our headline, cluster housing or a conservation subdivision also may be relevant in a suburb where one large tract of land has never been developed, but you'd like to save a big part of it for recreational or open space use.

The result of conventional zoning is that a subdivision’s open space is divided into individual lawns. In semi-rural situations, where the cluster housing terminology and concept seems to have gained the most traction, another important concept may be that the sewerage in a conventional subdivision is handled through individual septic systems, which require several acres.

In the typical cluster housing development or conservation subdivision, lots are sold individually, with a homeowners association taking possession of the conservation land. I've also heard of situations in which a non-profit organization is paid to manage the conservation land, without the homeowners association voting on specific proposals.

So Why Would Cluster Housing Be Better?

This seemingly new wrinkle in development practice actually is based on the very old concept of the village, with communal ground on the outskirts. There are several advantages to clustering the residences into one or possibly two or three parts of the subdivision:

• Development expense, and therefore housing affordability, will be lower, because of the lesser length and total area of roads to be developed. The linear nature of all of our utilities except broadband also means that this savings is multiplied with the addition of each utility. Fewer feet of pipe or wiring means less cost.

• Open space values will be higher. Open space leads to cleaner air, cleaner water, and uptake of greenhouse gas emissions. But connected open space enhances these values exponentially. Contiguous 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. It’s safe "room to roam" for the children. Groundwater recharge 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 flash flood prevention.

• Slightly larger septic systems or package treatment options for sewerage may become more feasible, allowing generally better results when the entire subdivision is responsible for maintaining one or a few sewerage facilities. If each owner is responsible, generally someone won't clean out the system frequently enough, and it might be the neighbor who suffers the consequences.

• Cluster housing also permits an element of sociability that rural families sometimes lack simply because the houses are further away. Smaller children can be allowed to visit other nearby children without having to make an automobile trip. So in many ways, cluster or conservation subdivisions allow the best of both suburban and rural living.

• Joint community facilities can be developed. Examples might be a fishing lake or a barn. While many of the resident families may not rely on agriculture for any or all of their income, they can still enjoy some of the amenities of agricultural life. There may be one portion of the parcel that would be particularly suitable for vegetable gardening, and perhaps all families who want to garden would do so in that general area.

• Sometimes the motivation for keeping a large percentage of an overall development parcel in a contiguous non-developed area would be recreational or aesthetic. 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.

How to Provide for Cluster Housing

When we use the phrase cluster zoning, we're assuming that the area has adopted municipal zoning. In many places where there is no zoning of agricultural land, that assumption may not be valid. However, the benefits of cluster housing development listed above still apply to what instead may be known as conservation subdivision.

Cluster housing usually results from flexible zoning that may be a variation on planned unit development or planned development. In a planned development zoning category, essentially a developer 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.

If the municipality or county zoning commission and/or governing body specifically want to encourage cluster housing or the conservation subdivision concept to maximize open space and minimize infrastructure requirements, it's better if you write a separate zoning classification rather than relying on your planned unit development provisions to do the job. This gives the government more specific criteria related to conservation or recreation.

You can explain that your cluster district or overlay option is a variation on PUD if you wish, but make the cluster housing requirements more specific. For example, you might require that 75% of the site remain undeveloped. 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. You can have minimum setbacks from property lines for various types of buildings also.

You can regulate signs, parking, 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, of course 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 will want to establish a minimum acreage for the entire cluster housing development. I'd think that number would be at least 10 acres.

You'll need a list of permitted uses in a proposed cluster zoning district, just as in any other 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.

Summary Recommendation on Conservation Subdivisions

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. This would differ from the planned development approach, in which typically the zoning is not assigned until the specific site plan is available. But if you pre-assign an area for cluster development, prospective purchasers and neighbors will be aware of the plan for future limited residential development. Plus you can select the land you most wish to preserve for habitat conservation.

3. Of course, rezoning applications to allow cluster housing also should be permitted.

4. You will need to 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.

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