Accessory Dwelling Units

An ADU is generally an additional living area independent of the primary dwelling that may have been added to, created within, or detached from the primary dwelling. The ADU must have basic requirements for living, sleeping, cooking, and bathroom facilities on the same parcel as the primary dwelling. See Special Property Eligibility Considerations, for complete ADU eligibility requirements.

When reporting the living area of an ADU, it should not be included with the Gross Living Area calculation of the primary dwelling. It should be reported and adjusted for on a separate line in the grid, unless the ADU is contained within or part of the primary dwelling with interior access and above grade. If a standalone structure does not meet the ADU minimum requirements, it should be treated as any other ancillary structure and included as a separate line item in the sales comparison approach then adjusted based on its contributory value to the subject property.

Whether a property is defined as a one-unit property with an ADU or a two- to four-unit property will be based on the characteristics of the property, which may include, but are not limited to, the existence of separate utility meter(s), a unique postal address, and whether the unit can be legally rented. The appraiser must determine compliance with this definition as part of the analysis in the Highest and Best Use section of the appraisal. When there is an ADU, the appraisal report must include a description of the ADU and analysis of any effect it has on the value or marketability of the subject property. The appraisal report must demonstrate that the improvements are acceptable for the market. An aged settled sale will qualify as a comparable, and an active listing or under contract sale will qualify as a supplemental exhibit to show marketability.

Zoning for an ADU

If it is determined that the property contains an ADU that is not allowed under zoning (where an ADU is not allowed under any circumstance), the property is eligible under the following additional conditions:

• The underwriter confirms that the existence will not jeopardize any future property insurance claim that might need to be filed for the property.

• The illegal use conforms to the subject neighborhood and to the market.

• The property is appraised based upon its current use.

• The appraisal report states that the improvements represent a use that does not comply with zoning (“illegal” use).

• The appraisal report demonstrates that the improvements are typical for the market through an analysis of at least two comparable sales with the same non-compliant zoning use. Aged settled sale(s) with the same non-compliant zoning use are acceptable if recent sales are not available. At a minimum, the appraisal report must include a total of three settled sales.

See Site Section of the Appraisal Report, for subject property zoning information.