Accessory Dwelling Units

Accessory Apartments

This type of accessory unit results when a small apartment is created within a house or added as an attached unit. The accessory apartment may be located on a level separate from the main living area, such as the basement or attic, or be in a separate wing or section of the single-family house. It could also be planned as a unit over or within an attached garage. These units typically have a separate entry. These types of units have been referred to as in-law apartments, garage apartments, or family apartments.

Accessory Cottages

These ADUs are separate, small houses that are sited on the property of a single-family home. The unit can be conventionally built, although there are several examples of modular designs that are brought to the property and sited on a foundation. These may be a permanent structure or temporarily placed on the property. These units have been referred to as ECHO (Elderly Cottage Housing Opportunity) houses, granny flats, and carriage houses.

Community Benefits

A community that allows for or encourages the use of accessory dwelling units may have several reasons for doing so. First, a plan for ADUs addresses the community's need for rental housing and for smaller affordable units that may be attractive to younger workers. The community can increase this supply without spending community funds. Second, it increases the community's housing supply without developing more land. This helps preserve undeveloped land and reduces costs associated with providing water and sewer lines to new developments. In communities with little developable land or with growth restrictions, utilizing ADUs may be an important opportunity to increase the supply of housing. Third, the assessed value of a house or property that adds an ADU will increase, thus increasing the property tax base for the community. Fourth, ADUs can help a community address a housing dilemma facing many older homeowners who have a large family home that they no longer use or manage effectively.

Homeowner Benefits

Homeowners with large homes or lots may find that subdividing their house and adding a small rental housing unit provides extra income that offsets some of the expenses of the house and makes the house more affordable to the homeowner. Some homebuyers may look for this type of housing to help offset the costs of their mortgage payments. Older people living on fixed incomes may find an on-site rental property especially helpful. The secondary unit ensures that there will be a neighbor close by, increasing the sense of security, and there may be agreements with the tenant to assist in home maintenance and yard care.

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