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Many jurisdictions limit the size of ADUs through one or more of the following: maximum square footage, percentage of the size of the primary dwelling, and/or overall lot coverage. Size limits related to the primary house or lot size effectively penalize smaller primary homes, which will not be able to add full-sized ADUs. Explicit size requirements in ADU ordinances usually range between 750 and 1,000 square feet. Increasing the allowable lot coverage for ADUs can also add flexibility into city codes. Portland, Oregon allows up to 15 percent of total lot coverage to be taken up by detached structures on a property. Washington County in Oregon also gives a 15 percent size bonus for ADUs that are ADA-accessible. Another approach with small houses on large lots is to allow the new dwelling to become the primary structure while the original house is designated as an ADU. .............................................................................................................. - ADOPTED: PORTLAND, VANCOUVER (B.C.), CALIFORNIA F, P9 lid Parking matters largely because of the space it takes away from housing. Off-street parking requirements also add construction costs and can make pedestrian -friendly design more challenging. Research has shown that occupants of ADUs are generally less likely to own a car, compared to residents of detached homes.' Forty percent of ADU occupants in California do not park a car on the street, while another 46 percent park only one car on the street.8 Parking requirements are also more strongly correlated with ADU applications than other standards, such as unit size or permit fees: California cities with no off-street parking requirements are more than twice as likely than other cities to receive at least one ADU application per month.' .............................................................................................................. _ ADOPTED: SEATTLE, VANCOUVER (B.C.), SAN FRANCISCO, OREGON Other regulations hindering ADU construction are large setback requirements, lower height caps, occupancy limits, and requiring separate utility connections to the street. High permitting costs and fees can also impact the financial feasibility of ADUs. Portland, Oregon permanently waived - system development charges (impact fees for water, parks, and roads that would total about $19,000-$24,000) for ADUs in 2018; the waiver is not available to properties used for short-term rentals. ups sir � 91 all�� 6 E I M ■r�:+'LT#r' ai0FV-