5.2 Auxiliary Dwelling Units - Mark Jurchen

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Creating (or Understanding) an ADU Zoning Code The ADU section of a community's zoning code needn't be overly complicated. It just needs to establish clear,objective and fair rules for the following: 1.A Definition:A good zoning code clearly defines its 7. Design Standards: terminology. Here,for example,is a useful outline for what, • Size and height:A zoning code might specify exactly in the real world,is a very fluid term:"An ADU is a smaller, how large and tall an ADU is allowed to be. For secondary home on the same lot as a primary dwelling.ADUs instance:"An ADU may not exceed 1,000 square feet are independently habitable and provide the basic or the size of the primary dwelling,whichever is requirements of shelter,heat,cooking and sanitation." smaller."Codes often limit detached ADUs to 1.5 or 2 2.The Purpose:This is where the code describes key stories in height.An example of that language:"The reasons a community allows ADUs.They should: maximum height allowed for a detached ADU is the • increase the number of housing units while respecting lesser of 25 feet at the peak of the roof or the height the style and scale of the residential neighborhood of the primary dwelling." • bolster the efficient use of existing housing stock and • Parking:Most zoning codes address the amount and infrastructure placement of parking.Some don't require additional • provide housing that's affordable and responds to the parking for ADUs,some do,and others find a middle needs of smaller,changing households ground—e.g.,allowing tandem parking in the driveway and/or on-street parking. (See page 16 for • serve as accessible housing for older adults and people more about parking.) with disabilities • Appearance:Standards can specify how an ADU's 3. Eligibility:Who can build an ADU and on what type of roof shape,siding type and other features need to lot?A statement in this part of the code clarifies that an match the primary dwelling or neighborhood norms. ADU can be placed only on a"residentially zoned lot." Some codes exempt one-story and internal ADUs from (Some communities provide lot size standards.) such requirements. (See page 16 for more.) 4.Creation:The code sets out how an ADU can be built. 8. Additional Design Standards for Detached ADUs: For instance:"An ADU may be created through new construction,the conversion of an existing structure,as an • Building setbacks:Many communities require addition to an existing structure or as a conversion of a detached ADUs to either be located behind the qualifying existing house during the construction of a new primary dwelling or far enough from the street to be primary dwelling on the site." discreet. (A code might exempt preexisting detached units that don't meet that standard.) Although such a 5. Quantity:Most municipalities that permit ADUs allow rule can work well for neighborhoods of large one per lot.Those allowing two typically permit one properties with large rear yards,communities with internal and one external.Some allow duplexes or smaller lot sizes may need to employ a more flexible townhomes to have an ADU,either in the backyard or on setback-and-placement standard. the ground floor. • Building coverage:A code will likely cap the 6. Occupancy and Use:A code should state that the combined lot coverage of a detached ADU and the use-and-safety standards for ADUs match those used for the primary dwelling to a specific percentage. main dwelling on the property. (See page 17 for more.) • Yard setbacks:Most communities have rules about Visit AARP.org/ADU to download Accessory Dwelling minimum distances to property lines and between i Units:Model State Act and Local Ordinance,a free buildings on the same lot.ADUs are typically required a publication that can be used by state and local officials to follow the same rules. to develop ADU policies. The ABCs of ADUs I AARP 15