Studying the Benefits of Accessory Dwelling Units

Left, 1415 Allston Way; right, 1843 Berryman Street.
Left, 1415 Allston Way; right, 1843 Berryman Street.

Students and faculty at the College of Environmental Design have long designed creative approaches to increasing density in residential neighborhoods. But California’s implementation of SB 375, the Sustainable Communities and Climate Protection Act of 2008, is putting new pressure on communities to support infill development. So the timing could not be more perfect for the Institute of Urban and Regional Development’s Center for Community Innovation to study small-scale infill, specifically, the potential impact of an accessory dwelling unit strategy in the East Bay.

In-law units, or accessory dwelling units (ADUs), are self-contained, smaller living units on the lot of a single-family home. They can be either attached to the primary house, such as an above-the-garage unit or a basement unit, or, as is more typical in Berkeley, an independent cottage or carriage-house. They are an easy way to provide homeowners with flexible space for a home office or an on-site caregiver, additional rental income, or a space for elderly family members to remain in a family environment. In short, they offer the kind of flexibility that has become imperative in today’s world to accommodate fluctuating work schedules and alternative family arrangements.

Left, 2601 Derby Street; right, 1822 Virginia Street.
Left, 2601 Derby Street; right, 1822 Virginia Street.

The concept, often termed “invisible density” or “distributed housing,” is hardly a new idea — indeed, the practice of building a supplementary unit behind a main house has been prevalent in Berkeley and throughout the East Bay for over a century. But ADUs particularly fit the context of Berkeley’s flatlands, with their historically “blue-collar urban form.” These “minimal-bungalow” districts are characterized by neat regularity, uniform land use, and little change — making them ideal for ADU development. Developers in the 1910s and 1920s widened the lots from 25 feet to 40 feet, created uniform setbacks, and supplied single backyard garages in order to maintain lower densities in the neighborhood. CED Professor Paul Groth argues that this uniformity was meant to create more predictable land values and erase the visual evidence of class struggle seen in more mixed-use, informal districts by imposing middle-class values. But today, the wide lots and historic garages provide an opportunity for infill.

ADUs provide benefits for both society and individuals. As infill development, they make efficient and “green” use of existing infrastructure and help increase densities to levels at which transit becomes viable — yet with lower costs and quicker permitting processes than for larger, multi-family building types. Because ADUs tend to be relatively small and their amenities modest, they provide more affordable housing options (at less than one-third of the cost of comparable units in multi-family buildings). Oftentimes, these units are the only rental housing available in older, predominantly single-family neighborhoods, making it possible for people from all walks of life to live in the area. Yet, they also significantly improve the value of the property, in essence constituting an asset-building strategy for homeowners.

Left, Ventura Avenue at Marin Avenue; right, Edwards Street at Channing Way.
Left, Ventura Avenue at Marin Avenue; right, Edwards Street at Channing Way.

The Center for Community Innovation (CCI) is studying the potential to add detached ADUs on single-family lots in Berkeley and other East Bay cities as a way to moderately increase density, provide homeowners with extra income, and create affordable rental units — all while preserving the character of existing neighborhoods. Based solely on lot size requirements and the square footage of existing structures, tens of thousands of homeowners could construct ADUs. However, a closer look at city regulations reveals other barriers to scaling up the strategy. Most importantly, most cities require the property to provide space for two parking spots — one for the existing single-family home, and another for the ADU.

CCI is studying ways to relax these off-street parking requirements without contributing to neighborhood parking problems. In neighborhoods near Bay Area Rapid Transit (BART) stations, residents may not need to own a car, particularly if car sharing is available. Car sharing services like Zipcar and City CarShare allow members to access a car whenever they need one, without the hassle of owning — and parking — their own individual vehicles. By finding ways to integrate ADU development with transit ridership and car sharing, CCI hopes to facilitate the development of sustainable, affordable housing options in Berkeley’s neighborhoods. The study will be available by fall 2011.

Virginia Street.
Virginia Street.

But the biggest barrier is perhaps psychological. Homeowners regularly fight neighbors’ plans to alter their property. Though they may object to a building’s form and appearance, or the loss of privacy in their own backyards, more likely they are concerned about the impacts of increased car parking on the street. Sensing the objections of the neighbors, homeowners balk at improving their own property, even if it makes financial sense. And ironically, the homeowners who would most benefit from the improvement — whether because they live in older small houses or because their family income is unstable — are often themselves reluctant or fearful of assuming the new financial obligation.

The best way to overcome these fears is by demonstrating the benefits and value of ADUs. Luckily, a CED class on sustainable design, taught by Ashok Gadgil from the Lawrence Berkeley National Lab, was the genesis of a demonstration project — a model cottage in my West Berkeley backyard. Students analyzed zoning requirements and developed preliminary designs for a net-zero-energy cottage. Energy efficiency measures, such as well-insulated walls, reduce the building’s electricity usage, while a new solar photovoltaic system removes the cottage and the main house from the electricity grid. Built for $100,000, and rented for $1,200 per month, the cottage not only makes financial sense but also demonstrates how careful design can make a small space beautiful. That there is significant interest in the idea became apparent during our open house in January 2011, which attracted almost 500 people.

Net-zero-energy affordable unit located in author Karen Chapple’s backyard.
Net-zero-energy affordable unit located in author Karen Chapple’s backyard.

The next step is to demonstrate the value of scaling up an ADU strategy. The CCI study is analyzing the potential impact of constructing thousands of these units in the East Bay. In economic terms, the impact is significant. A $100,000 ADU generates an additional $80,000 of indirect and induced spending in the economy, and if most purchases are made locally, each ADU creates one year-long local job. Thus, construction of 4,000 ADUs locally would mean 4,000 local jobs. New property taxes could feed city coffers. And, each net-zero-energy ADU creates energy savings that impact the local economy. If households save $25 in energy costs each month, construction of 4,000 ADUs could thus mean an additional $1.8 million spent on local goods and services each year. If the new households are clustered, they may be able to help the region’s struggling retail corridors become more viable.

Other impacts we are evaluating pertain more to resource use, particularly in California. Distributed generation will reduce dependence on utility-produced energy. Incorporation of greywater systems — for instance, recycling water for irrigation needs — at a large scale could reduce pressure on California’s water supply. And clustered demand for alternative transportation modes could make local car share and transit systems more sustainable.

Ultimately, though, an academic study will not persuade policymakers to scale up this strategy. What should happen next is another demonstration project, this time on a larger scale. What if the local utility, water, housing, and transit agencies, working closely with the cities, sponsored a pilot program that incentivizes homeowners to build 100 ADUs in the region? Such a pilot could help overcome homeowner inertia, and would also demonstrate the benefits of scale to the agencies themselves. The precedent for this exists in the pilot energy-efficiency programs that cities, funded by federal stimulus dollars, have been offering to local homeowners. CED and its research centers look forward to providing a venue that spurs this conversation — and results in a more sustainable Bay Area and California.

A Call for New Ruralism

New Ruralism is a framework for creating a bridge between Sustainable Agriculture and New Urbanism. Sustainable agriculture can help bring cities down to earth, to a deeper commitment to the ecology and economy of the surrounding countryside on which they depend.


New Ruralism embraces the power of place-making that can help American agriculture move from an artificially narrow production focus to encompass broader resource preservation values. As a place-based and systems-based framework, the New Ruralism nurtures the symbiotic relationship between urban and rural areas. To build this bridge, the Institute of Urban & Regional Development (IURD) and Sustainable Agriculture Education (SAGE) are jointly launching a project on New Ruralism.

The Rationale for New Ruralism

To thrive and endure, regions and the cities within them need a vital local agricultural system that encompasses individual farms, rural communities, and stewardship of natural resources. As it stands, rural areas – especially those at the urban edge – face enormous challenges. In California, as in many parts of the developed world, agricultural operations near cities are under extreme pressure from suburbanization, environmental degradation, and an industrialized and globalized farm economy. Urban areas are contending with the flip side of this problem: the multiple costs of sprawl and a national crisis of health problems related to diet, exercise, and the built environment. Too many urban residents are increasingly overfed and undernourished. They are disconnected from rural and natural surroundings that further recede with increasing low-density auto-dependent urbanization. In many ways, industrialized agriculture and urban sprawl are similar blights, both operating with little regard to the natural conditions of the landscape and oblivious to the ecological and cultural uniqueness of place.

New Ruralism is built on twenty years of reform – in food, agriculture, and land use planning. The sustainable agriculture and local food systems movements have taken organic foods mainstream, made farmers’ markets a basic town-center amenity, and put “slow food” on a fast track. At the same time, New Urbanism projects and Smart Growth initiatives have demonstrated the possibilities of creating healthier, more livable urban centers. Communities large and small are utilizing smart growth tools to create mixed use, pedestrian-friendly and transit-oriented developments; to encourage infill, revitalize downtowns, institute ‘green’ building policies, and better balance the growth of jobs and housing. New Urbanism acknowledges farmland and nature to be as “important to the metropolis as the garden is the house”. Yet approaches for strengthening the vitality of surrounding rural areas as a means to contain and sustain cities have not been thoroughly investigated. In many ways, New Ruralism is now where New Urbanism and Smart Growth were two decades ago – powerful ideas that were being generated mostly by professionals, out of sight of public and academic views.


kraus_3Just as New Urbanists and ‘critical regionalists’ have articulated and demonstrated the potential for a renewed movement of place-affirming urban planning, our regional rural areas need a similar call to action. We are positing New Ruralism as a corollary of New Urbanism with a related framework of principles, policies, and practices, and with the following as its preliminary vision statement:

New Ruralism is the preservation and enhancement of urban edge rural areas as places that are indispensable to the economic, environmental, and cultural vitality of cities and metropolitan regions.

New Ruralism draws from past models. Some obvious examples are the agrarian context for the ‘Garden City’ and the self-sufficiency elements of eco-villages. New Ruralism also incorporates current initiatives, such as sustainable city charters, local food policy councils, the agricultural land trust movement, and mechanisms to preserve and enhance regional agriculture and its natural resource base. Most importantly, New Ruralism can harness marketplace forces such as demand for rural lifestyle, countryside view, and food with ‘terroir’ (a taste of place).

The geography for New Ruralism can be generally defined as rural lands within urban influence; the larger the metropolis, the larger the field of influence. The geographical structure of metropolitan regions extends out from the urban-rural interface and the rural-urban fringe to exurbia and beyond, to urban-influenced farmland. It is too often a contested landscape of transitional land uses, speculative land values, regulatory uncertainty, and impermanent agriculture. The current default attitude in this area is that metropolitan agriculture inevitably dissolves and retreats as the urban footprint expands.

Within this field of urban influence, the New Ruralism movement would help create permanent agricultural preserves as sources of fresh food for the larger urban region, and as places for nurturing urban connections with the land. These could take the form of green food belt perimeters, buffers between urban areas, small agricultural parks at the urban-rural interface, or bigger preserves further a-field that include larger farms and rural settlements. This vision must work hand in hand with the New Urbanism vision of compact mixed-use urbanized areas, the elimination of low-density auto-dependent sprawl, and distinct “edges” between towns and their surrounding rural working lands.


kraus_4These ideas for a vision and geography for New Ruralism provide a starting point for some preliminary principles.

New Ruralism would denote specific, named rural places located near an urban area and part of a broader metropolitan region. Such New Ruralist places would have an identity rooted in their unique and significant agricultural, ecological, geographical, and cultural attributes. This identity would contribute to a broader regional sense of place, through local farm products, rural activities, iconic landscape, and opportunities for public experience. These rural places may also have general designations as agricultural preserves or ‘appellations’ or ‘local food belts’.

The primary land use would be small to medium scale sustainable agriculture integrated and overlapping with areas for wildlife and habitat management and for passive recreation. Conducive agronomic conditions and agricultural history would be primary factors determining the location of such agricultural preserves. Other factors would include dedicated current farmers and identified aspiring farmers; crops and livestock distinctive to the place; processing and marketing infrastructure; affordable housing on farms or in nearby communities for farm employees; and regulations supportive of value-added enterprises and agritourism operations. The ‘Wild Farm’ movement demonstrates the potential value of this kind of multifunctional agriculture.

Urban-rural connectivity would be a multi-faceted exchange. A major linkage would be in the form of ‘locally grown food’, promoted through direct marketing channels and through institutional networks. ‘Local food-shed’ is an attribute ripe for quantification and even certification, due to its value-added connotation of fresh, healthy and flavorful food and its potential for public access and interaction. (Such a place-based designation has long been used for wines and is now being used for crops tied to place and method of production.) Connectivity would also take the form of physical links to urban green spaces and to regional hiking, equestrian, and biking trail systems. Another linkage is the arena of environmental services. Services such as green waste composting, aquifer recharge, flood and fire protection, and preservation of biodiversity would be part of the urban-rural economic exchange and would help re-establish the value of the ecological structures that underlie the jurisdictional patchwork.

New Ruralist agricultural preserves would welcome the public as both visitors and residents. One of the highest values of rural areas near cities is their attraction as homesites for people who are not farmers. With careful planning, this bane can be a boon. Affirmative agriculture easements and projects such as Vineyard Estates in Livermore and the Qroe[1] model in New England demonstrate the potential for successful symbiosis of estate homes with agriculture, as valued landscape. However, the benefits of country life should not be limited to the wealthy. Following both the demand for ‘rural lifestyle’ and the trend for the ‘not-so-big-house’, clustered, modest non-farm rural home homesites have the potential to be a key value proposition for preserving agricultural land, especially if they are strictly limited and their value is tied in to the local agricultural economy. Perhaps these homeowners can purchase a “share” of the farm production along with their modest dwellings.

The development and management of each agricultural preserve would be guided by a comprehensive plan. Such a plan could be established and implemented as a join powers agreement between city and county agencies where necessary. Broader regulations and incentives would likely also come into play. The key to establishing rural places reflecting metropolitan regional values is a holistic approach that integrates a wide range of goals for public health, conservation, economic development, housing, agricultural productivity, and more. Within a template framework, each plan might also have specific quantified objectives, such as goals for local food production or local jobs or educational programs. Through these plans, New Ruralist places would capture and compensate landowners for specific “public good” amenities provided for the local town or broader metropolitan region.

In summary, these ideas for a New Ruralism vision and principles are exploratory, intended to provoke discussion and response. Key questions are:

  • How can the concept of New Ruralism be most useful for advancing the common goals of sustainable agriculture/local food systems movement and the new urbanism/smart growth movement?
  • Does New Ruralism provide a meaningful framework for analyzing past models and present initiatives for harmonizing city and countryside?
  • What are the key elements required for it to succeed and what long term benefits would accrue from these successes?
  • Can New Ruralism be applied as a construct in actual planning projects and be advanced into governmental regulations?
  • Can a New Ruralist vision, illuminated by key models, help galvanize the public support and private investment necessary to create urban edge agricultural preserves?

During the coming months, through workshops and white papers, IURD and SAGE plan to continue to explore these and other questions. We welcome your thoughts on our preliminary ideas.

[1] The Qroe Company develops and manages real estate properties that integrate conservation, farming and housing.