How to Build an ADU in San Francisco

Posted on
July 29, 2020

Since2003 when the government code was changed to allow for a streamlined permit approval of the second-unit on a property, nothing significant was made to help homeowners build ADUs. One of homeowners’ challenges still remained to afford paying the architectural fees to find out the size and budget of an ADU for their own property, before committing to the project. In the last just few years, technology has enable proptech companies to create tools to check quickly and very affordable what are the ADU options specific to a property. Once you know what you may be allowed to build, an ADU builder can give you a more accurate bid for your project .Now, you just multiply the maximum square footage to the average per square foot value in your neighborhood and you’ll be amazed to see how much value you can add to your property

Accessory Dwelling Units (ADUs),also called secondary units, in-law units, or cottages, are units added to existing or new residential units on a property. This program applies to both single-family and multi-family buildings. In this article, we'll cover the procedure on getting the permit to add and ADU to existing single-family homes.

On August 31, 2018, Mayor London N. Breed issued an Executive Directive to accelerate the approval of Accessory Dwelling Units ( ADUs), and to clear the backlog of pending applications. This directive comes along with the City's initiative to increase density in order to overcome the housing shortage in San Francisco.

Now, home owners have full support from the city to add ONE (1) more unit to their existing home of four (4) or less legal dwelling units. If your home is eligible for the Voluntary Seismic Retrofit Program, you may be eligible to add more than one ADU. For more information on the Voluntary Seismic Retrofit Program, please visit Let's see how you can benefit from it.

ADU or no ADU?

First lets see if your property is eligible for  ADU. You can find out this information in your Value Added or New House report. Hopefully, you are one of the lucky ones that are Eligible for ADU.

‍Waiver or No Waiver?

City of San Francisco leaves the back door opened for exceptions to the current code. Those of you whom the existing building allows for an ADU under current code regulations, are called "NO Waiver" ADU. For those of you whose property would require some exceptions from the code, are called "Waiver" ADU.

Here you can find out if you are a "NO waiver" or a"Waiver" ADU.

An  Accessory  Dwelling Unit  ( ADU)  is  a  residential  unit added  to  an  existing  building.  ADUs are subordinate to the primary residential unit(s), generally due to their location on the lot and/ or the size of the unit. Also known as  Secondary Units,  In-Law Units,  or Granny Flats,  ADUs are generally developed using underutilized spaces within a lot, whether a garage,  storage,  rear  yard, or  an  attic.  These units are independent from the primary unit that  have  their  own  kitchens, bathrooms  and  living  areas.  

ADUs can be located:

  • within the existing building;
  • as an extension to the existing building;
  • or as a separate structure on the same lot as the primary unit

Types of ADUs

There are four ADU types:

  1. Conversion ADUs are new units that convert space in a residential building.
  2. Attached ADUs are new units that expand a residential building.
  3. Detached ADUs are new free-standing buildings located on a residential property.
  4. Junior ADUs (JADU) are a new type of ADU that convert up to 500 square feet of space in a single-family structure. JADU requires owner-occupancy in either the remaining portion of the single-family home or the newly created JADU.

ADUs' size:

  • not larger then 50% of the primary residence
  • up to 16 ft in height (on a sloped lot the height may be different)
  • interior spaces have to follow the building department guideline

Answer these few questions about your project to find out if you may qualify to get advantage of the benefits California offers to the home owners who want to add more units on their property.

Want to get your permits fast?

Will my ADU be rent controlled?

ADUs added to existing single family homes will not be subject to rent control, unless a “waiver” from a Planning Code requirement, such as the open space or exposure requirement, is granted.

Can I use my ADU for short-term rentals?

No. Accessory Dwelling Units are ineligible for the Short Term Rental program.

Can I Sell my ADU?

No. ADUs under this program cannot be subdivided and sold separately. It can only be sold with the primary residence.

Review Process: What’s involved?

If the proposed ADU is within the existing built area of your single-family home, the review process will be straightforward and should take less than 120 days. Planning Department will review and provide comments at the counter. If the proposed ADU includes an addition to the existing home for an ADU, this will likely be reviewed by all City agencies within four months, and neighborhood notification is not required for ADUs 1,200 square feet or smaller. If the proposed ADU is proposed in conjunction with construction of a new home plus ADU, neighbors within 150 feet of the subject property and relevant neighborhood groups must be notified for a 30-day public review period; the timing of this will vary. The Discretionary Review process will also apply, similar to all other expansion permits reviewed by the Planning Department.

If you're looking to buy a house or you're a real estate agent interested to see the development opportunities of any property? Here is how you can find out FREE ...

10 STEPS to complete an ADU project


Calculate the size and location of the ADU you may be allowed to have on the property. Sounds complicated and expansive. In this case, your Value Added or New House report. If your property has an existing legal building in the rear yard, such as a garage or storage shed, this may be eligible for converting into an ADU

If you're looking to buy a house or you're a real estate agent interested to see the development opportunities of any property? Here is how you can find out FREE ...


Decide on how this ADU can serve you best. Is this unit helping you pay the mortgage by creating a rental apartment? Is it going to house multi-generational households or an older homeowner could move to the ADU while the children live in the main home? Depending on its primary use, you might realize that the size of the ADU may not be satisfy your final goal.


Take your Value Added or New House report to the Planning Department for a pre-application meeting. Submit a screening form to the Department of Building Inspection (DBI).


Design your project and finalize construction drawings. We, at CityStructure can help you with the drawing set if you need assistance.


Contact contractors to get cost estimates and time frame for the project. Here is a good article about the costs you'd have to take into consideration when putting together the budget.


Get information about financing. If you'd like to see how long it'll take to make a profit by renting your ADU, here is a calculator.


The Planning Department and other city agencies review. If expansion is proposed this process will include Neighborhood Notification. We advise to hire a professional to put together the set of drawings for permits, unless you've already done so on step Four.


Building permit is issued, all fees paid.


Hire a contractors. Start construction!


Once the construction is completed, schedule the final inspection with the city inspector. If not objections are made during the inspection, you should get the Certificate of occupancy. Now you have the ADU ready for your tenant to move in!

Find out if your project qualifies for streamline permitting under Senate Bill 9 (SB9) to get the permits fast

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