In response to the housing crisis in the Bay Area, California passed multiple bills in October that made it easier for California residents to build an ADU on their property. Redwood city granny flats are on the rise due to this reason. 

Property owners are building additional dwelling units for the immense benefits that come with them.

While the perks of building a granny flat may be endless, navigating local and state ordinances can be off-putting.

Current Regulations for Redwood City

Redwood City has been making big leaps to help make it easier for residents to build ADUs onto their property.

Some of the current regulations in place include:

  • No maximum unit size limit under 850 square feet for a one-bedroom ADU.
  • For a two-bedroom ADU there is no maximum unit size limit under 1,000 square feet.
  • The unit cannot cover more than 50% of the rear yard area.
  • The entrance for the unit must be accessed by a side-hinged swinging door, so a garage or patio door cannot be used.
  • All garage conversions that are attached to the main house that has fire sprinklers are required to also have sprinklers.

Figuring out if your lot is viable to build an ADU can be challenging, Maxable offers a free ADU Planning Phone Call to help you with your ADU project!

Building Height

  • The maximum height is 28 ft.
  • Structures must not exceed 2.5 stories
  • Detached units must not exceed the building height of the primary dwelling unit on the same lot.

Setback Requirements

Thanks to AB 881 and AB 68, setbacks requirements have been minimized to four feet for the side and rear.

Legally permitted structures, like a garage, do not need to conform to setback regulations as long as all eaves two feet or less from the property line are removed. This makes garage conversions ideal for ADUs.

Parking Requirements

If you are converting your garage, you are not required to come up with additional parking for an ADU that is within a half-mile walking distance of public transportation.

Residential Hillside and R-1 Zoning District Exceptions

There are some exceptions to some regulations for lots 10,000 square feet or greater in the Residential Hillside or Residential Single-Family (R-1) Zoning Districts.

These include:

  • The maximum allowable floor area can be 800 square feet instead of the usual 700 square feet.
  • You can have no more than 2 bedrooms, whereas, in other Redwood City areas you are only allowed 1 bedroom.

Redwood City Granny Flats Permitting & Property Tax Costs

  • Creating an ADU requires a building permit. The price for this permit varies by cost of construction, square footage, design, and number of bedrooms. 
  • You’ll also need a planning permit
  • Under the rules of Prop. 13, the Office of the County Assessor appraises new construction at fair market value when the improvements are complete. The value of the new construction is added to the total assessed value of the property, changing your property tax rate.

Maxable can help you find out the actual cost of your granny flat project. Get started with a free phone consultation to get your questions answered.

Local Permitting Resources

Permitting is one of the most difficult and daunting steps when it comes to ADUs.

You can find out which specific permits you need for your zone here.

Other Common Questions about ADUs in Redwood City

Is there a specific guideline I have to follow when designing my ADU?


You must have a similar exterior to the primary dwelling unit, such as similar roofing, siding, windows, and doors.

Can the homeowner live offsite and rent both the primary dwelling unit and the ADU?

Starting in 2020 there will be no more owner-occupancy regulations due to the bills that passed in October.

Are you required to build a kitchen in an ADU?


Each ADU has to have a kitchen that includes a stove, oven, a sink and a food preserving appliance.

How do I get started on my ADU project?

Starting such a huge project can seem overwhelming. 

Trying to navigate regulations, permitting, and design can be difficult.

To make things easier schedule a free ADU Planning Phone Call with one of Maxable’s granny flat specialists!