Housing density and housing-unit cost

How Much Land is Needed to Develop a Cohousing Community?

by Lynn Englund

When I first became interested in cohousing, one of the questions I had was: how much land would a cohousing group need to purchase in order to develop their community? I’ve learned that it depends on several factors, including the values and lifestyle that a cohousing community desires, the amount of money the group can pull together, and the zoning regulations of the municipality.

For example, a community that values extensive green space and gardens probably will seek more land than a community that values living in the city near a light-rail corridor. A community that can afford to purchase more land might prefer single-story homes. An urban-transit-oriented group may find that buildings of three or more stories are required by the city.

If you attended Twin Cities Cohousing Network’s December 2, 2016 meal and meeting, you might have noticed a rotating slide presentation illustrating typical housing types at different housing densities. This article goes more in depth, with examples of cohousing communities as well as other sources of information to further explain how housing density is connected to the amount of land that a group might purchase.

Housing density is a measure of the average number of dwelling units on an acre of land, often abbreviated DU/acre (dwelling units per acre). This measure does not tell us anything about how large or small each dwelling unit might be, but the limitations of the lot size and local zoning regulations will constrain how dwelling units may be arranged (or stacked) on the site. Average density will also vary depending on how many acres are included in the calculation. For example, the average housing density of a large area of a city that includes schools, churches, businesses, parks, and roads will be lower (fewer DU/acre) than the housing density of just one strictly residential block in an area of the same city, and especially so if that block has a preponderance of multi-story, multi-family residential buildings.

Although cohousing communities are often developed for a total of 20-35 households, the amount of property owned by the community may range in size from many acres to a relatively small parcel equivalent to a few city housing lots. Cohousing architect Chuck Durrett claims that cohousing built at a density of 10 units per acre is a “sweet spot” for a variety of reasons, and a number of the communities he has designed have been built at about that density. I have provided links to a number of existing cohousing communities (not all designed by Durrett) to help readers learn how housing density affects the amount of land a cohousing group will need.

Stone Curves Cohousing, Tucson, AZ (Google map).
9.4 DU/acre. This community of 48 units was developed on 5.1 acres about five miles north of downtown Tucson. It consists of five clusters, or “villages;” each village is made up of two four-townhouse buildings on either side of a pedestrian path. The community also incorporates a 3,850 sq. ft. common house.

Fresno Cohousing, Fresno CA (Google map)
10 DU/acre. Fresno Cohousing consists of 28 dwelling units on 2.8 acres in a residential area of the city that is adjacent to a Unitarian-Universalist Church. The community consists of attached row houses facing each other across a shared pedestrian sidewalk.

Arboretum Cohousing, Madison, WI (Google map)
18.2 DU/acre. Developed for 40 households on a 2.2 acre site, Arboretum Cohousing is located one mile from downtown Madison and the same distance from the UW campus. Two new three-story multi-family buildings house 29 households. The community also includes a duplex, triplex, and six free-standing houses.

Eastern Village Cohousing, Silver Springs, MD (Google map)
56 DU/acre. This “green” community with 56 units is located in the downtown arts and entertainment district, and was created by rehabbing an abandoned four-story office building. The building’s horseshoe shape allows for a central courtyard area. I spied a playground and green roof at the top.

Capitol Hill Urban Cohousing, Seattle, WA (Google Map)
90 DU/acre. Although on the small side with only nine units, this new cohousing community was created on just one-tenth of an acre in the vibrant (and expensive) Capitol Hill neighborhood. The community also owns commercial space on the ground floor that is leased to architects who live in the community.

As someone who enjoys living with the convenience of a light-rail station out my building’s front door, I understand that property in this area is zoned for high-density residential and commercial uses, and that makes it expensive! The way it becomes more affordable is to build at higher densities. What that looks like here is taller buildings than might be found in less transit-intensive neighborhoods. Those who desire lower housing densities (fewer DUs/acre) may be forced to look for property farther from the center of the Twin Cities.

Another resource that I found to be very helpful in getting a sense of how housing density “feels” in a neighborhood, and how it “looks” in terms of building style and height is a document titled, “Density Fact Sheets – Corridor Development Initiative” (2005).* This document (download PDF here) shows many examples from Twin Cities neighborhoods that may be familiar to the reader and that are of varying densities. *Prepared for the Minneapolis Corridor Housing Initiative by the Metropolitan Design Center at the College of Architecture and Landscape Architecture, University of Minnesota.

Studying all of these communities and examples helped me to visualize housing density and understand some of the variations in cohousing design. Assuming a cohousing community is designed for 30 households, the amount of land a group might seek could vary from more than 3 acres, if developed at a density of 10 DU/acre, to less than ½ acre, if developed at 60 DU/acre. It might even be developed as a single floor, or section, of a very large high-rise building with hundreds of residences.
Lynn Englund is interested in how people organize social interactions and communities to promote health through the lifespan. She is a founding member of Hearth Communities, a group of friends that has been socially active for more than 25 years. Recently, she has taught graduate students in the parent and family education program at the University of Minnesota, and has provided leadership to revive Twin Cities Cohousing Network, an organization that promotes the development of cohousing communities.