Secondary suite

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Secondary suites, or accessory dwelling units, ADUs, or in-law apartments, are self-contained apartments, cottages, or small residential units, that are located on a property that has a separate main, single-family home, duplex, or other residential unit. In some cases, the ADU or in-law is attached to the principal dwelling or is an entirely separate unit, located above a garage or in the backyard on the same property.[1] In British English the term "annexe" is used instead. Reasons for wanting to add a secondary suite to a property may be to receive additional income, provide social and personal support to a family member, or obtain greater security.[2]



Naming conventions vary by time-period and location but secondary suites can also be referred to as an accessory dwelling unit (ADU), mother-in-law suite, granny flat, coach house, laneway house, Ohana dwelling unit, granny annexe, granny suite, in-law suite, and accessory apartment.[3] The prevalence of secondary suites is also dependent on time and location with varying rates depending on the country, state, or city.[4] Furthermore, regulations on secondary suites can vary widely in different jurisdictions with some allowing them with limited regulation while others ban them entirely through zoning, limit who may live in the units (for example, family members only), or regulate if units can be rented.[4][5][6][7]

Relationship to main residence[edit]

Common types of secondary suites

A secondary suite is considered "secondary" or "accessory" to the primary residence on the parcel. It normally has its own entrance, kitchen, bathroom and living area. There are three types of accessory units: interior, interior with modification, and detached. Examples of these accessory units include:

  • A suite above a rear detached garage (a "garage apartment"),
  • A suite above the main floor of a single-detached dwelling,
  • A suite below the main floor of a single-detached dwelling (a "basement suite").
  • A suite attached to a single-detached dwelling at grade, or
  • A suite detached from the principal dwelling (a "garden suite" or "guesthouse").
  • A habadu, granny flat, or laneway house are other names for an habitable accessory dwelling unit.


Communities that support secondary suites may do so to support a diverse set of goals. Commonly cited benefits of secondary suites include the following;.

  1. Creating more affordable housing options as secondary suites are typically small, easy to construct, increase housing supply, and require no land acquisition.[8][9][10][11]
  2. Enabling seniors to "age-in-place" by creating smaller more affordable units where seniors can downsize in their own neighborhood.[12][9] Some of the recent popularity of secondary suites in the United States can be attributed to the activism of the American Association of Retired Persons (AARP) and other organizations that support seniors.[9]
  3. Supporting diverse and multi-generational households as seniors, young-adults, or other relatives can live on the same property as their families but still maintain some independence and privacy.[12][9][8][13][14] For seniors, this kind of arrangement can improve their social life, allow family members to easily provide care, and allow them to live in more walkable neighborhoods when they can no longer drive.[15][16][17]
  4. Improve home maintenance and homeownership rates by providing a reliable rental income which can support mortgage payments or home maintenance.[8][18][9]
  5. Creating energy efficient housing as the small and often attached units require fewer resources.[19][12]
  6. ADUs can be integrated into the scale and character of single-family neighborhoods while also promoting workforce housing in these neighborhoods.[12][20]
  7. Municipal budgets may benefit from new taxable housing that does not require new or significant utility upgrades, road maintenance, etc.[8]

By country[edit]


Dual occupancy is sometimes used to refer to the development of two dwellings on one allotment of land. They may be either attached (semi-detached) or detached.[21] The term is common in Australia. A dual occupancy can be either torrens titles or strata titled.

A 'dual occupancy' in Victoria, Australia is a means to add value to property through a subdivision of one lot into two. It is that subdivision that makes dual occupancy an attractive proposition for new property investors and developers.

A 'granny flat' in Australia is actually also known as a secondary dwelling on a property, which is totally different from a dual occupancy. It does not require subdivision of the land and its construction requires approval from the council or relevant authority. The certifying process between council or a private certifier depends on a few conditions.


CMHC (Government program)[edit]

The Canada Mortgage and Housing Corporation provides a financial assistance program to help Canadians create affordable housing for low-income seniors and adults with a disability within a secondary suite. The program is called the Residential Rehabilitation Assistance Program (RRAP) -- Secondary/Garden Suite. The maximum fully forgivable loan depends on the location of the property:

  • Southern Areas of Canada: $24,000/unit
  • Northern areas of Canada: $28,000/unit
  • Far northern areas: $36,000/unit

A 25% supplement in assistance is available in remote areas.[22]

British Columbia[edit]

The Housing Policy Branch of British Columbia's Ministry of Community, Aboriginal and Women’s Services published a guide for local governments to implement secondary suite programs called 'Secondary Suites: A Guide For Local Governments'.[23] The current issue is dated September 2005. The intent of the guide is to "help local governments develop and implement secondary suite programs". It also highlights good secondary suite practices as well as providing practical information to "elected officials, planners, community groups, homeowners, developers, and others interested in secondary suites".


In Norway, particularly in the bigger cities, it is quite common to build separate adjoined smaller flats for renting out. The owner of the main flat will rent out the smaller adjoined flats.

United States[edit]

In the United States, secondary suites are generally referred to as accessory dwelling units or ADUs. An ADU is second complete dwelling unit which is legally built within or on the same lot as an existing single family residence. An ADU provides complete independent living facilities including a kitchen, bathroom and its own entryway. ADUs are typically not allowed to be sold separate from the primary home and the homeowners are usually required to reside in one of the two units.[24] State laws typically delegate planning and zoning powers to city and county governments which specify the appropriate type, distribution and intensity of land uses in the local jurisdiction.[25] As a result, the feasibility of building an accessory dwelling unit (ADU) (also known as a secondary suite, second unit, granny cottage, etc.[26]) can vary widely from place to place, depending on state law and each local jurisdiction's willingness to adopt regulations that facilitate ADUs.

Popular in the early 20th century, ADUs fell into disfavor after WWII, when a shift to suburban development occurred with emphasis on the nuclear family. However, with increases in the price of housing in many cities and suburbs, an increased awareness of the costs of low-density car-oriented development patterns and an increased need to care for the aging baby boom generation, ADUs have been promoted by some as a beneficial option.[27] However, some critics perceive ADUs to be a threat to the character of single-family residential neighborhoods.

Several states have enacted legislation to promote accessory dwelling units. In California, Government Code Sections 65852.150, 65852.2 & 65852.22 pertain to local regulation of ADUs.[28] SB 1069 and AB 2299 are California bills approved in 2016 and effective January 1, 2017, that limit local government authority to prohibit ADUs in certain cases (and also reduce cost and bureaucracy hurdles to construction).[29][30][31][32] The states of Vermont[33][34] and New Hampshire[35][36] have also adopted a number of bills that promote accessory dwelling units and reduce regulatory barriers to ADU construction. The State of Illinois considered, but did not adopt, HB4869 which would have required municipalities to permit (and reasonably regulate) accessory dwelling units (ADUs).[37]

Several local governments across the United States have enacted ordinances to both permit and promote accessory dwelling units. Some cities have included accessory dwelling units in larger missing middle housing and affordable housing strategies including Seattle,[38][39][40][41] Portland,[42][43][44] and Minneapolis.[45][46][47][48][49][50][51]. Many other communities have maintained wide-spread single-family zoning but still updated codes to permit accessory dwelling units. Notable examples include large cities such as Los Angeles, CA[52] and the City of Chicago, IL.[53] Diverse smaller jurisdictions that permit accessory dwelling units include as Lexington, KY,[54] Santa Cruz, CA.[55][56] and the County of Maui in Hawaii.[57]

Honolulu, Hawaii, has "Ohana Dwelling Units," which although similar to ADUs, limit occupancy to "family" and have other regulatory requirements.[58] Ohana Dwellings in Hawaii were created as an allowed use in the zoning code in 1981 as a way to encourage the private sector to create more housing units (without government subsidy), preserve green fields (open space) and ease housing affordability.[59][60][61] In 2015, Honolulu amended its zoning code to add a new use—ADUs[62]—as a sort of Ohana Dwelling, but with fewer restrictions. To prevent creating further complexities for existing Ohana Dwellings, some of which have been condominimized and owned separately from the main house, Ohana Dwellings remain an allowed use (with different requirements and benefits than ADUs) in the zoning code. Due to the poor turnout in the number of ADUs, Honolulu added incentives in 2016, waiving permit fees.[63] Fee waivers were extended in 2017.[64] ADUs are an important component to Honolulu's Affordable Housing Strategy.[65]

See also[edit]


  1. ^ "Smart Growth / Smart Energy Toolkit - Accessory Dwelling Units (ADU)". Retrieved 2016-10-02.
  2. ^ "Smart Growth / Smart Energy Toolkit - Accessory Dwelling Units (ADU)". Retrieved 2016-10-02.
  3. ^ Eli Spevak, Orange Splot LLC and Melissa Stanton, AARP Livable Communities (2019). The ABCs of ADUs (PDF). AARP.CS1 maint: multiple names: authors list (link)
  4. ^ a b Brinig, Margaret; Garnett, Nicole (2013-01-01). "A Room of One's Own? Accessory Dwelling Unit Reforms and Local Parochialism". Journal Articles.
  6. ^ "Accessory Dwelling Units". American Planning Association. Retrieved 2021-02-21.
  7. ^ Karen Chapple, Jake Wegmann, Farzad Mashhood, and Rebecca Coleman. "JUMPSTARTING THE MARKET FOR ACCESSORY DWELLING UNITS: LESSONS LEARNED FROM PORTLAND, SEATTLE AND VANCOUVER" (PDF). San Francisco chapter of the Urban Land Institute.CS1 maint: multiple names: authors list (link)
  8. ^ a b c d Coppage, Jonathan (March 2017). "ACCESSORY DWELLING UNITS: A FLEXIBLE FREE-MARKET HOUSING SOLUTION" (PDF). R Street.
  9. ^ a b c d e Brinig, Margaret; Garnett, Nicole (2013-01-01). "A Room of One's Own? Accessory Dwelling Unit Reforms and Local Parochialism". Journal Articles.
  10. ^ MRSC. "Accessory Dwelling Units Issues & Options" (PDF).
  11. ^ Florida Housing Coalition. "Accessory Dwelling Unit Guidebook" (PDF).
  12. ^ a b c d Communities, AARP Livable. "ADUs Are Good for People and Places". AARP. Retrieved 2021-02-21.
  13. ^ "American Planning Association". American Planning Association. Retrieved 2021-02-21.
  14. ^ Nichols, Jane Louise; Adams, Erin (2013-03-01). "The Flex-Nest: The Accessory Dwelling Unit as Adaptable Housing for the Life Span". Interiors. 4 (1): 31–52. doi:10.2752/204191213X13601683874136. ISSN 2041-9112.
  15. ^ PhD, Phoebe S. Liebig; MSG, Teresa Koenig; PhD, Jon Pynoos (2006-11-21). "Zoning, Accessory Dwelling Units, and Family Caregiving". Journal of Aging & Social Policy. 18 (3–4): 155–172. doi:10.1300/J031v18n03_11. ISSN 0895-9420. PMID 17135101.
  16. ^ EDITORS: Chrysanthe Broikos, National Building Museum, Melissa Stanton, AARP Livable Communities, CONTRIBUTORS: Caitlin Bristol, National Building Museum | Sarah Watson, CHPC | Danielle Arigoni, AARP Livable Communities. "Making Room: Housing for a Changing America" (PDF).CS1 maint: multiple names: authors list (link) CS1 maint: extra text: authors list (link)
  17. ^ Binette, Joanne; Vasold, Kerri. "2018 Home and Community Preferences: A National Survey of Adults Ages 18-Plus". AARP. Retrieved 2021-02-21.
  18. ^ U.S. Department of Housing and Urban Development Office of Policy Development and Research. "Accessory Dwelling Units: Case Study" (PDF). HUD User.
  19. ^ "Studying the Benefits of Accessory Dwelling Units". Frameworks. 2011-04-21. Retrieved 2021-02-21.
  20. ^ "Promoting Workforce Housing Expanding Locations and Development Potential". Montgomery County Planning Commission.
  21. ^ Planning & Land Management, Territory Planning Branch (2002). "Dual Occupancy Review" (PDF). Retrieved August 21, 2008.
  22. ^ Residential Rehabilitation Assistance Program (RRAP) -- Secondary/Garden Suite Archived 2006-09-09 at the Wayback Machine
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  29. ^ SB 1069:
  30. ^ AB 2299:
  31. ^ Pender, Kathleen (2016-12-03). "New California housing laws make granny units easier to build". San Francisco Chronicle. Archived from the original on 2018-06-15. Retrieved 2018-07-12.
  32. ^ Wong, Queenie (2016-09-27). "California eases restrictions on 'granny units'". San Jose Mercury News. Archived from the original on 2016-10-19. Retrieved 2018-07-12.
  33. ^ "Bill Status S.237 (Act 179)". Retrieved 2021-02-07.
  34. ^ "ACCESSORY DWELLING UNITS". State of Vermont Agency of Commerce and Community Development.
  35. ^ "Accessory Dwelling Units". New Hampshire Housing. Retrieved 2021-02-07.
  36. ^ "ACCESSORY DWELLING UNITS IN NEW HAMPSHIRE: A Guide for Municipalities" (PDF). State of New Hampshire, Housing.
  37. ^ "Illinois General Assembly - Bill Status for HB4869". Retrieved 2021-01-03.
  38. ^ "Neighborhood upzones for affordable housing: Q&A on proposal with Seattle mayor's adviser". The Seattle Times. 2018-05-09. Retrieved 2020-04-26.
  39. ^ "SEATTLE CITY COUNCIL - Record No: CB 119444". Retrieved 2020-04-26.
  40. ^ "SEATTLE CITY COUNCIL - Record No: CB 119544". Retrieved 2020-04-26.
  41. ^ "Accessory Dwelling Unit - SDCI |". Retrieved 2021-02-19.
  42. ^ "Better Housing by Design project documents". Retrieved 2021-02-13.
  43. ^ "About the Residential Infill Project". Retrieved 2021-01-24.
  44. ^ "Portland just passed the best low-density zoning reform in US history". Sightline Institute. 2020-08-11. Retrieved 2021-01-24.
  45. ^ "Owner-Occupancy Requirement for Accessory Dwelling Units Amendment". Retrieved 2021-02-19.
  46. ^ "Residential Buildings with up to Three Units". Retrieved 2020-04-26.
  47. ^ "Housing". Retrieved 2020-04-26.
  48. ^ Kahlenberg, Richard D. (2019-10-24). "Minneapolis Saw That NIMBYism Has Victims". The Atlantic. Retrieved 2020-04-26.
  49. ^ "Three Cheers for Minneapolis (The 3 is for Triplex)". Strong Towns. Retrieved 2021-01-24.
  50. ^ "Allowing Intentional Community Cluster Developments". Retrieved 2020-04-26.
  51. ^ PBS NewsHour (November 23, 2019). "How Minneapolis became the first to end single-family zoning". Youtube.
  52. ^ "ADU | DRP". Retrieved 2021-01-24.
  54. ^ "ADU proposal". City of Lexington. Retrieved 2021-01-24.
  55. ^ "City of Santa Cruz Accessory Dwelling Unit Development Program". Retrieved 29 October 2015.
  56. ^ "ADU". Retrieved 2021-01-24.
  57. ^ "Maui County Zoning Code, Section 19.35". Retrieved 15 August 2011.
  58. ^ City and County of Honolulu. "Revised Ordinances of Honolulu, (ROH) Section 21-8.20" (PDF). Land use Ordinance. Retrieved 15 August 2011.
  59. ^ "Ohana Housing Program Evaluation". Honolulu: Office of Information and Complaint. September 1984. Retrieved 15 August 2011.
  60. ^ Lau, Questor (May 2014). "Black boxes and gray spaces: how illegal accessory dwellings find regulatory loopholes". Retrieved 4 August 2016.
  61. ^ "Ohana Zoning a 5 year review" (PDF). State of Hawaii Legislative Reference Bureau. Retrieved 22 January 2015.
  62. ^ "Honolulu Ordinance 15-41 Relating to Accessory Dwelling Units" (PDF).
  63. ^ "ADU Status Update". 11 February 2017. Retrieved 2017-07-19.
  64. ^ "Honolulu mayor signs ADU incentive bill into law". KHON2 News. 2016-07-21. Retrieved 2017-07-19.
  65. ^ "Implementing [Honolulu's] Affordable Housing Strategy" (PDF). Honolulu Office of Housing. Retrieved 2017-07-19.

For New South Wales, the two approval paths are available. 1. If the Frontage of the land is 12m or more, a CDC (Private certifier) is possible. If less, then it must go through a DA(Council). 2. If above condition is met, another important requirement is the land size. If your land size is 450sqm or over, we can do a CDC approval. If it is less than 450sqm, we have to lodge the secondary dwelling application through the council.

External links[edit]