Smart Growth / Smart Energy Toolkit Accessory Dwelling Units Smart Growth / Smart Energy Toolkit Accessory Dwelling Units (ADU)

Smart Growth / Smart Energy Toolkit Accessory Dwelling Units

Smart Growth / Smart Energy Toolkit

Accessory Dwelling Units Accessory Dwelling Units (ADU)(ADU)

Accessory Dwelling Units Accessory Dwelling Units (ADU)(ADU)


• An Accessory Dwelling Unit is a secondary housing unit on the same property as a main residence.

• ADUs are also called accessory apartments, in-law apartments, family apartments, or secondary units.

• ADUs are not duplexes :– Size of ADU is subsidiary to the main residence– Owner of ADU usually lives on the property

• ADUs are self-contained

What is an ADU?What is an ADU?


Why consider an ADU Why consider an ADU bylaw?bylaw?

• Shrinking household size

• Rising real estate costs

• Aging population

• Neighborhood stability

• Character of neighborhoods

• Environmental benefits


What does it do for you?What does it do for you?• Municipality:

– Increases tax revenue– Minimizes subsidies required for

affordable units– Maximizes use of existing infrastructure

and services– Keeps growing and aging families

together– Preserves existing homes and

historic structures– Promotes safe and stable neighborhoods


Who benefits from ADUs?Who benefits from ADUs?

• Homeowners – rental income

• Middle-income tenants – more units

• Local businesses – employee housing

• Real estate firms – rental stock

• Residential contractors – remodeling

• Lending institutions – home improvement loans


Affordable ADUsAffordable ADUs• Local Initiative Program can be an

instrument for affordability• ADU qualification conditions for MA

Subsidized Housing Inventory (SHI)– Unit approved by local bylaw and DHCD– Unit occupied by income-eligible tenant

(≤80% of area median income)– Unit rented at affordable price over term

of control

• For SHI details, contact Department of Housing and Community Development at www.mass.gov/dhcd


Who typically chooses to Who typically chooses to build ADUs?build ADUs?

• Older singles/couples

• Middle-aged "empty nesters"

• Younger singles/couples

• Single working parents

• People who travel often


• Apartments in single-family homes

• Additions to homes

• Conversion of garages or barns

• Free-standing cottages

• Designed into new construction

How and where are ADUs How and where are ADUs built?built?


ADUs and Neighborhood ADUs and Neighborhood TypeType

Traditional Neighborhood Blocks

Features:• Shallow lots, with or without

alley• Carriage houses and garages

at the back of the lot• Original carriage houses

small single bay buildings• ADUs sited along alley

frontage or rear property line



Transitional Neighborhood Blocks

Features:• Pre-war grid blocks with pre-

and post war housing• Deep lots• Garages located in rear

yards• ADUs placed within garage

zone in rear yards



Suburban Neighborhood Blocks

Features:• Cul-de-sac blocks• Small yards• Parking in front of lot with

20’ driveway parking• ADUs sited in rear lot

areas on bigger lots and/or garage conversions


ADU Option 1: Apartments ADU Option 1: Apartments within Single-Family Homeswithin Single-Family Homes


ADU Option 2: Additions to ADU Option 2: Additions to Single-Family HomesSingle-Family Homes


ADU Option 3: Conversion ADU Option 3: Conversion of Garages, Barns, of Garages, Barns,

OutbuildingsOutbuildings


ADU Option 4: Construction ADU Option 4: Construction of New Outbuildingsof New Outbuildings


ADU Option 5: Designed ADU Option 5: Designed into New Constructioninto New Construction


Regulation of ADUsRegulation of ADUs• Zoning ordinance/bylaw

– Specifies ADU conversion standards

• As-of-Right– For interior alterations

• Special Permit– For exterior changes and out buildings

• Licensing– Periodic appraisal of ADU via renewal

or for change in ownership


Summary of ADU Summary of ADU BenefitsBenefits

• Creates new housing using existing infrastructure and services

• Reduces energy consumption• Generates community dollars

through home equity• Reduces costs for the elderly• Preserves housing stock and

neighborhood stability


Selected MA Selected MA communities with ADU communities with ADU

bylawsbylaws• Case studies

– Pelham, rural community– Lexington, suburban community– Northampton, urban community


Additional InformationAdditional Information

• MA Housing Partnership (MHP)http://www.mhp.net

• MA Department of Housing and Community Development (DHCD)http://www.mass.gov/dhcd/

• Background on Subsidized Housing Inventoryhttp://www.mass.gov/dhcd

• Older Americans Act websitewww.aoa.dhhs.gov


Additional InformationAdditional Information• ‘Taking the Initiative – A Guidebook on Creating Local

Affordable Housing Strategies’, CHAPA and MHP, Chapter 3, pp. 49-51 (March 2003)http://www.mhp.net/uploads/resources/taking_the_initiative_guidebook__ch._111.pdf

• ‘Granny Flats Add Flexibility and Affordability’, New Urban News Ithaca, NY, New Urban Publications, (2001)http://www.newurbannews.com/accessory.html

• ‘Accessory Apartments’, Leo L. Cram, Missouri Gerontology Institute, University of Missouri (1993)http://muextension.missouri.edu/explore/aging/gg0014.htm

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Smart Growth / Smart Energy Toolkit Accessory Dwelling Units Smart Growth / Smart Energy Toolkit Accessory Dwelling Units (ADU)