is a San Francisco architecture firm, practicing user centered design for commercial and residential projects.

KWAN DESIGN ARCHITECTS is a San Francisco architecture firm, practicing user centered design for commercial and residential projects.




Building Permit Questions


Safety is the primary reason for building code regulations. The building permit process is a way for the city to regulate the building codes. A building permit is needed for all renovation and new construction. In many cases, a building permit is also needed for repair or replacement of existing fixtures, such as windows replacement. A mechanical, electrical or plumbing permit maybe needed for changes or addition to the existing mechanical, electrical or plumbing system; for example, moving or adding an electrical outlet or a plumbing fixture requires a permit. Most building permits need drawings submitted to the city to show the improvements and the type of construction being proposed. Once the permit is issued, you're required to build the project and if any changes are made to the work, it must be made with the City's approval. Some permits can be issued over-the-counter while other permits require additional time for reviews. In San Francisco, a building addition permit can take approximately 24 months. Building codes were created for safety reasons. If you perform work without permit, then, it is a violation of codes and you will be subject to fines and penalties. You will also require to obtain permits for the work created and if the work does not comply with codes, you will have to demolish the work.

Some of the common building code questions.

Opening or Windows - Generally, openings such as windows are not allowed within 0 to less than 3 feet from the property line, unless the windows are facing a street or back yard. Limited windows areas are allow from 3 feet to less than 5 feet. For residential projects, openings are not limited when they are located at 5 feet or greater from the property line.

Ceiling Height - Generally, the minimum ceiling height is 7'-6"; Bathrooms, toilet rooms, kitchens, storage rooms and laundry rooms shall be permitted to have a ceiling height of not less than 7 feet.

Egress Window - The size of bedroom window for emergency escape in a wood frame non sprinkler residential buildings should have a minimum net clear open area of 5.7 square feet. The minimum net clear opening height shall be 24 inches. The minimum net clear opening width shall be 20 inches.

Natural Ventilation - The minimum net openable window to the outside is 4 percent of the area of the room.

Natural Light - The minimum net glass area is 8 percent of the floor area of the room.

Heating - Spaces for human occupancy shall be heated & maintain a minimum indoor temperature of 68°F at a point 3 feet above the floor.

Building Expansion - If you plan to expand your building, consider the following questions.

A.  Will the expansion trigger additional parking?  Most cities prefer to hide or recess the garage door. Some cities will allow one parking at the existing front landscape area as long as a percentage of landscape area remains, approximately 25%.

B. Has the building reached its maximum allowable size or floor area ratio (FAR)?

1.  In City of Millbrae, R-1 single family zone, the allowable area is 55% of the lot area.

2.  In San Francisco, the horizontal & vertical setbacks takes more precedent over percent of lot area coverage.

3.  In City of Sunnyvale, a single family house in R-0, R-1 and R-2 zone is 45% of the lot area.

4.  In the City of Burlingame, the maximum lot coverage is 40% for single family lots.

C.   Has the building reached its maximum allowable height limit? Most single family zones in San Francisco have a height limit of 40 feet. Most of the other neighboring cities are approximately 30 feet.

The following are some works exempt from permit per 2022 California Building Code (CBC). Please note that individual city may have their own interpretation & variation of the CBC.
1. One-story detached accessory buildings used as tool and storage sheds, workshops, playhouses and similar uses, provided the floor area is not greater than 120 s.f. I suggest that if the structure has a roof overhang, then, the projected roof area shall not be greater than 120 s.f.
2. Fences not over 7 feet high. For San Francisco, any fence not over 6 feet at the side or rear of the property & 3 feet in height along the front of the lot. Click Here for more information for fences in San Francisco.
3. Retaining walls that are not over 4 feet in height measured from the bottom of the footing to the top of the wall. If this wall is supporting a surcharge, then it will require a permit.
4. Water tanks supported directly on grade if the capacity does not exceed 5,000 gallons and the ratio of height to diameter or width does not exceed 2:1.
5. Sidewalks and driveways not more than 30 inches above adjacent grade and not over any basement or story below and not part of an accessible route.
6. Painting, wallpapering, tiling, carpeting, cabinets counter tops and similar finish work.
7. Temporary motion picture, television and theater stage sets & scenery.
8. Prefabricated swimming pools in 1 & 2 family dwellings in which the pool walls are entirely above, the pool is less than 24” deep and if the capacity does not exceed 5,000 gallons.
9. Shade cloth structures constructed for nursery or agricultural purposes, not including service systems.
10. Swings & other playground equipment accessory to detached 1 & 2 family dwellings.
11. Window awnings in 1 & 2 family dwellings & U occupancies, supported by an exterior wall that do not project more than 54 inches from the exterior wall and do not require additional support.
11. Nonfixed & movable fixtures, cases, racks, counters & partitions not over 5 feet 9 inches in height.


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.

Unit Legalization - In San Francisco, there is also a unit legalization program to help you legalize an in-law unit without the ADU process. In that process, the unit needs to be existed prior to January 1, 2013.

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.

Statewide ADU exemption

A statewide ADU exemption is an ADU of up to 800 s.f. , 16’ in height, as potentially limited by a local agency, and with 4’ side & rear yard setbacks. State ADU Law requires that no lot coverage, floor area ratio, open space, or minimum lot size will preclude the construction of a statewide exemption ADU.

1,000 s.f. ADU in Millbrae.

1,000 s.f. ADU in Alameda.

1,000 s.f. ADU in Millbrae

Senate Bill 9, SB 9

California State Senate Bill 9 (SB 9) would allow a 2 residential units development in a single-family residential zone to be considered ministerially, without discretionary review, public hearing & CEQA, if the development meets certain requirements by the local agency. SB 9 said this development approach does not require owner occupancy.  Neither unit would be subject to rent control & the units could be sold as condominiums. 

If your property is located within an urban area & your property was not established through a lot split prior to Senate Bill 9; Then you can subdivide your lot into 2 parcels and build 2 homes on each of the 2 new lots allowing for a total of 4 units. SB 9 said the lot split approach requires the applicant to occupy one of the units as their principal residence for a minimum of 3 years. SB 9 allows the local agency to ministerially approve a parcel map for an Urban Lot Split that meets certain requirements by the local agency.

The review & approval process under SB 9 will be “objective” in terms of zoning standards, subdivision standards, and design standards.

Key points to consider:

  1. Qualify Projects must be zoned in a single-family lot; Not a historic site or district; Cannot alter or demolish rent-controlled housing, housing that was Ellis Act in the last 15 years, or housing occupied by a tenant in the last 3 years.
  2. Minimum unit area 800 square feet.
  3. Minimum 4 feet setback at rear & side. (5 feet would be better in some situation)
  4. San Francisco requires minimum 25 feet separation between existing & new buildings.
  5. One parking per unit; Some local agency may consider no parking if parcel located ½ mile walking distance of transit.
  6. Cannot be use as short-term rentals.
  7. If units are attached, it must be design as condominium to allow for separate sale.
  8. Urban Lot Split should result in 2 approximately equal-sized lots (60-40 split). Each new lot is at least 1,200 square feet. Urbanized area is an area with 50,000 or more people. See US Census Bureau for urban area reference maps.