Cluster zoning is another technique intended to free the site designer from the rigidity of conventional, Euclidean zoning while still letting the community retain control of the overall effects of the development. Cluster ordinances, which generally apply to residential development, permit the building of houses on smaller lots, provided that the space thus saved is used for community purposes. For example, the zoning ordinance might specify a minimum lot size of half an acre, but cluster provisions permit building houses on quarter-acre lots provided that the completed development shall have no more houses in it than it could contain if developed with half-acre lots. The space saved is to constitute an open area accessible to all residents of the clustered area, often maintained by a residents' association.
Cluster zoning is very popular with planners. It permits the preservation of open space and reduces development costs. Placing houses closer together reduces the amount of road surface and utility line required per house. Smaller lots also mean less money spent per house on grading and other site-preparation costs.
Although clusters have been built in many communities, the cluster plan is often greeted with some public suspicion. The community sees the combination of closely spaced houses and open-space blocks, and suspects that sooner or later the open blocks will be filled in with housing. In point of fact, the permanency of the open blocks is easily protected with appropriate legal documents at the time the cluster development is approved by the community, but it can be difficult to convince a community that this is the case. With the passage of time and the accumulation of favorable experience, community resistance to clustering is diminishing.