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8.B. - Page 3 of 42 Figure 1— ADU Construction Height Foundation System ADU Height Ceiling Height — Floor 1 7'-6" or 8'-0" Floor Joists 1' Ceiling Height — Floor 2 7'-6" or 8'-0" Total w/Flat Roof: Plate Height 7'-6" or Plate Height 8' 17' or 18' Roof Pitch —4:12 (assuming 20' span) 3' Total 20' or 21' At the July 13th City Council hearing, a majority of the Council supported a 16 ft. height limit, while some councilmembers supported taller heights to allow more flexibility in ADU design, including the ability to have a livable second story. Based on the diagrams by the design consultant, a maximum height of 16 ft. would allow for a one-story building with loft space suitable for storage but not a second floor living area. An 18 ft. ADU would allow for a two-story with a flat roof and short ceiling heights, but adequate for living space and sleeping quarters. A 22 ft. ADU would allow for multiple designs for both a partial two-story ADU and a two-story ADU with full plate heights on the entire upper floor and a pitched roof. ADUs with lower heights could cause some architectural constraints to roof slope that may not allow an ADU to match the architectural style of the main home. The City Council also asked staff to compile ADU data from the last two years. In 2019 and 2020 a total of 143 ADUs were proposed and of those 21 (15%) were detached ADUs above 16 ft. in height. Detached ADUs over 16' height 2019: 11 (14%) Median height — 23.3' 2020: 10 (16%) Median height — 20.8' At the August 18th Planning Commission meeting staff recommended a maximum height of 16 ft. for detached ADUs, based on the discussion from July's Council meeting and the design diagrams. The Commission was in support of staff's recommendation, but they also expressed concerns with the height of attached ADUs which are allowed to be 4 ft. from the side and rear property line by State law. The Planning Commission recommended that ADUs attached to the main home that do not meet the rear yard setback (typically 20 ft.) should not be allowed to extend up to the height maximum of the underlying zoning district (typically 28 ft.). Attached ADUs would still be allowed to be constructed within the rear yard setback, but with a height limit of 16 ft. similar to the proposed height limit for detached ADUs. Staff supports the Commission's height recommendation as it would still allow for the construction of ADUs on virtually all residential lots and would retain the existing residential development pattern. Recommendation: 16 -foot maximum height for detached ADUs and for attached ADU that encroach within the required standard rear 20' setback. Attached ADUs not encroaching on the rear setback would be subject to the standard height requirement of the underlying zoning district (typically 28 ft.) Floor Area: State law requires allowance of an ADU of up to 800 sq. ft., exclusive of local FAR regulations, whether the ADU is attached, detached, located on the ground floor, or an upper floor. Attached ADUs Page 3 of 7 a City of Redwood City 1017 Middlefield Road, Redwood City, CA. 94063 Tel: 650-780-7000 www.redwoodcity.org 331