Accessory Dwelling Units

ADU, Accessory Dwelling Unit or JADU, Junior Accessory Dwelling Unit is a way to provide additional housing on the same lot. Its intention is to provide affordable housing options for renters, family members, the elderly, or caregivers. It can also help 1st time buyers to increase income to afford a new home. The following are some key points on ADU regulations:

Review period – An application for ADU or JADU for lots with a single-family dwelling shall be deemed approved, or denied, within 60 days from a completed application. The prior regulation was 120 days.
In San Francisco, if the ADU requires an expansion, neighbors within 150 feet radius and neighborhood groups will be notified for a 30-day public review period. During the 30-day period, a discretionary review process will apply.

Number of ADU allow – Under state law, you can provide (1) ADU and (1) JADU per lot, within the proposed or existing single-family dwelling, if certain conditions are met. For multi-family buildings, state law allows up to 25% of the unit count;

In San Francisco, if (4) or less legal dwelling units are on a lot, only (1) ADU is allowed. If (5) or more legal dwelling units are on a lot, then an unlimited number of ADUs are permitted under S.F. Planning Code. Then, the determination on the number of ADUs will depend on the S.F. Building Code for the abilities to provide natural light, ventilation, and two exits.

Size of the ADU – Under state law, the maximum size of a detached ADU is 1200 sq.ft. for more than one bedroom; local city requirements may vary. For example, the City of Millbrae is 1000 sq.ft. maximum for a detached ADU of more than one bedroom;

Size of the JADU – Under state law, the maximum size of a JADU within the primary dwelling is 500 sq.ft.; local city requirements may vary.

Density Limit – Adding an ADU does not change the allowable density limit of the lot.

Short-term Rentals – ADU cannot be used as short-term rentals.

Owner occupancy requirement – Owner occupancy is not required on ADUs until 2025, which means both the primary dwelling and the ADU can be rented.

For JADUs, owner occupancy is required at the primary dwelling or the JADU.

Rent Controlled – ADUs need to provide affordable rent to very low, low, or moderate-income households.

The information provided is for general reference; Every site has unique challenges, we have the training and experience to help you decide if an ADU makes sense for you from a cost, benefit & lifestyle point-of-view. If you think an ADU makes sense, we can help you to explore design options.

Urban Landscape, San Francisco, California

Nihonmachi Terrace is a high density Japanese senior housing complex in San Francisco Japan Center. The existing courtyard consisted of a lawn and a few trees that provided open space for the tenants and visitors. Kwan Design Architect (in association with Robert La Rocca Landscape Architect) revitalizes the courtyard in response to Japanese garden design principals, natural features and sustainable design solutions. The new courtyard included rock garden with raked gravel, pathways and wooden bridges over a dry creek, plants indigenous to the mountains, water scriptural feature, community vegetable garden, windbreak elements and gathering opportunities.

The Clarendon house, San Francisco, California

The Clarendon house is a 25 foot wide zero lot line property situated on the northern slope of Twin Peaks. The back of the house slopes down and has views from Golden Gate Bridge to downtown and the Bay Bridge. In an effort to preserve these views for the neighboring properties, the expansion was created below the existing house. The program required a 3 bedroom house with large living areas and contemporary style.

The design process was not the “traditional project delivery process” where the owner hires an architect to prepare drawings, then the owner hires a general contractor to bid and build the project. The traditional process creates communication problems and has higher chance of cost increase during construction. In the “traditional project delivery process”, the architect and contractor boundaries are more restricted.

Clarendon was designed under an “integrated project delivery process” where the owner requires a level of sophistication and a willingness to get involved. Contractor and suppliers were appointed from the beginning. The architect issued drawings in a collaborative relationship with the owner, contractor and suppliers. Decisions are made when they need to be made to eliminate redundant work. Contractor and suppliers are able to share their knowledge and expertise when it is most valuable in the design process.

stair at 1st Floor

Rotunda House, Millbrae, California

This project is located within the 65 CNEL Aircraft Noise Footprints based upon the Federal Aviation Administration (“FAA”) 1983 CNEL Noise Exposure Map.  If the properties within this map is constructed after Jan. 1st 1983, or is renovated at a cost equal to 25% or more of the current market value of the home, it must be insulated against aircraft noise to meet FAA noise insulation program standards.  This means that the windows must have a Sound Transmission Class (or STC) rating of 35.  A typical interior wall with one layer of 1/2″ gypsum board on each side of wood stud at 16” on center has an STC of approximately 33.

The window manufacturer we selected cannot provide STC 35 certification as a whole window assembly but the glass itself will perform the STC rating of 30 – 35.  We explained the situation with the building official and were able to obtain approval with the glass specification.

Click here for list of homes in the noise exposure area.

Click here for project images