Research

Select ADU Publications:

Implementing the Backyard Revolution: Perspectives of California's ADU Owners

The results of the first-ever statewide ADU homeowner survey. This report shares findings from 752 Californian homeowners who successfully constructed an ADU regarding the characteristics of those building ADUs, the local approvals process, construction costs, the construction process, ADU rental tenure, and rental prices throughout the state. 

April 2021
Authors: Karen Chapple, Dori Ganetsos & Emmanuel Lopez


ADUs in California: A Revolution in Progress

A comprehensive overview of California Accessory Dwelling Unit (ADU) permitting and building trends, barriers to development, best practices to promote ADU production, and the emergence of efforts to promote other types of small-scale multi-unit housing. Includes findings from a survey of California jurisdictions, interviews with key stakeholders, and data on the location of ADU permits and completions.

October 2020
Authors: Karen Chapple, Audrey Lieberworth, Dori Ganetsos, Eric Valchuis, Andrew Kwang & Rachel Schten


Reaching California's ADU Potential: Progress to Date and the Need for ADU Finance

In collaboration with the Terner Center for Housing Innovation

The Terner Center for Housing Innovation and Center for Community Innovation’s joint analysis of the increase in ADUs throughout California and the need for increased financing options for low- and moderate-income homeowners.

August 2020
Authors: Karen Chapple, David Garcia, Eric Valchuis & Julian Tucker


The ADU Scorecard: Grading ADU Ordinances in California

Our assessment of over 200 local ADU ordinances both for consistency with 2018 California State legislation and user-friendliness of the jurisdiction’s ADU programs for homeowners.

Interim Report – February 2020
Authors: Karen Chapple, Audrey Lieberworth, Eric Hernandez, Dori Ganetsos, Alejo Alvarado & Josie Morgan


A Solution on the Ground: Assessing the Feasibility of Second Units in Unincorporated San Mateo County

This report explores the potential for ADU construction in unincorporated San Mateo County. The report begins with an analysis of the physical feasibility of construction and then describes the potential market for ADUs. Following an analysis of financial barriers for different types of homeowners, a conclusion offers policy recommendations.

September 2017
Authors: Karen Chapple, Somaya Abdelgany, Alison Ecker & Sonrisa Cooper


Jumpstarting the Market for Accessory Dwelling Units: Lessons Learned from Portland, Seattle, and Vancouver

Findings from a 2017 ADU owner survey in Portland, Seattle, and Vancouver.

July 2017
Authors: Karen Chapple, Jake Wegmann, Farzad Mashhood & Rebecca Coleman


Financing Ancillary Apartments on Residential Properties: Challenges and Solutions

A report by the UC Berkeley Institute of Governmental Studies

The blocked market for financing small apartments on residential properties, and what the State of California can do about it.

August 2015
Author: Jake Wegmann


Scaling up Secondary Unit Production in the East Bay

This paper begins by analyzing how many secondary units of one particular type, detached backyard cottages, might be built in the East Bay, focusing on the Flatlands portions of Berkeley, El Cerrito, and Oakland. We then investigate the potential impacts of scaling up the strategy with regard to housing affordability, smart growth, alternative transportation, the economy, and city budgets. A final section details policy recommendations, focusing on regulatory reforms and other actions cities can take to encourage secondary unit construction, such as promoting carsharing programs, educating residents, and providing access to finance. 

October 2012
Authors: Jake Wegmann, Alison Nemirow & Karen Chapple


Yes, But Will They Let Us Build? The Feasibility of Secondary Units in the East Bay

This paper examines the regulatory barriers that must be solved in order to scale up  a secondary unit strategy.

October 2012
Authors: Alison Nemirow & Karen Chapple


Yes in My Backyard: Mobilizing the Market for Secondary Units

A 2012 report highlighting ADUs as a viable infill housing product.

June 2012
Authors: Karen Chapple, Jake Wegmann, Alison Nemirow & Colin Dentel-Post


"Hidden" Density: The Potential of Small-Scale Infill Development

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. As metropolitan planning organizations struggle to communicate the need for density, they should take note of strategies that make increasing density an attractive choice for neighborhoods and regions. 

June 2012
Author: Karen Chapple