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9.A. - Page 3 of 43 <br />The City's 2019 ADU Ordinance allowed a second -story ADU above a detached garage of up to 20 ft. in <br />height plus additional height for roof slope. As this provision of the City ADU ordinance is consistent with <br />State law, applications for ADUs above a detached garage would be reviewed with a height maximum up <br />to 20 ft. plate height and additional height for roof slope , with 4 ft. setbacks from side and rear property <br />lines, until a local ordinance is adopted. Other second -story ADUs would need to abide by the height <br />maximum of the underlying zoning district, typically 28 ft. <br />The factors that determine the height of a structure include lot slope, floodplain, foundation systems, <br />ceiling joist thickness, building code requirements for habitable space ceiling heights, and roof slope. <br />ADU Construction <br />Foundation System <br />Height <br />4"-12" <br />Ceiling Height — Floor 1 <br />7'-6" or 8'-0" <br />Floor Joists <br />1' <br />Ceiling Height — Floor 2 <br />7'-6" or 8'-0" <br />Total w/Flat Roof: Plate Height 7'-6" or <br />Plate Height 8' <br />17' or 18' <br />Roof Pitch — 4:12 (assuming 20' span) <br />3' <br />Total <br />20' or 21' <br />The Planning Commission recommended (6-1) a height limit of 16 ft. for detached ADUs and for attached <br />ADUs within the rear setback area. Although some Commissioners were in favor of a taller height, there <br />was an interest in moving the ordinance forward and an assessment that setting a taller height would <br />require further community and City Council deliberation. The Commission also expressed concerns with <br />the height of attached ADUs which are allowed to be 4 ft. from the side and rear property line by State <br />law. The Planning Commission added an amendment that ADUs attached to the main home that do not <br />meet the rear yard setback (typically 20 ft.) should not be allowed to extend up to the height maximum <br />of the underlying zoning district (typically 28 ft.). <br />On November 23, 2020, the City Council introduced ADU ordinance amendments with a 16 ft. height limit, <br />however some Councilmembers supported taller heights to allow more flexibility in ADU design, including <br />the ability to have a livable second story. On December 21, 2020, the second reading of the ADU ordinance <br />was pulled from the consent calendar for discussion, which was focused on the proposed height limit for <br />detached ADUs. The ADU ordinance amendments were not adopted and some Councilmember comments <br />included interest in increasing the height limit to allow a potentially taller two-story detached ADUs. <br />Public comment through several hearings has been mixed with both support for a 16 ft. height limit and <br />support for a taller height that would allow for a detached two-story ADU with livable second floor space. <br />Support for a 16 ft. height has included concerns regarding the bulk and mass of two-story structures <br />located four feet from neighboring property lines, privacy concerns of adjacent second story windows <br />that can look into adjoining rear yards, and concerns about future State law updates that would continue <br />to limit the City's ability to regulate the size and location of ADUs. A 16 ft. height would still allow for the <br />construction of ADUs on virtually all single-family residential lots. <br />Public comment also included support of height maximums taller than 16 ft. to allow flexible design <br />options where one-story limits may be too restrictive, allow both a detached standalone two-story ADU <br />Page 3 of 7 <br />City of Redwood City 1017 Middlefield Road, Redwood City, CA. 94063 Tel: 650-780-7000 www.redwoodcity.org <br />67 <br />