San Bernardino County ADU Regulations & Zoning

San Bernardino County ADU Regulations and Zoning Information
What is all the buzz about ADUs in San Bernardino County? Want to learn about The San Bernardino County ADU regulations? An ADU is an Accessory Dwelling Unit (aka Granny Flat or a small home) that can be built in your backyard and used for extended family or friends or as a rental property. It can be attached or detached from the main house.

The State of California is leading the nation in ADU development and regulations, and its ADU handbook provides a great summary.

One of the most affordable types of ADUs is a prefabricated home. One of San Bernardino County’s most active prefabricated ADU builders in San Bernardino County is USModular Inc. “ADUs are becoming very popular for homeowners looking to generate rental income in their backyard or for families that have children or elderly parents moving home, as it gives everybody their own space, is affordable and ADU increases the value of the property,” says Todd Kesseler, CEO of USModular Inc.



Some of the Highlights of the State of California ADU Regulations Include:

  • Every residential property in California is allowed to have one ADU of up to 800 sq ft regardless of lot size, floor area ratio, or main residence size.
  • This ADU can be up to 16 ft in height.
  • Homeowners are allowed to build one attached ADU or one detached ADU and one JADU, all on the same property.
  • Cities must allow at least 850 sq ft for one-bedroom ADUs and at least 1,000 if the ADU has two or more bedrooms. Cities cannot impose smaller max sizes, but they can impose larger. Every City has specific regulations for size and bedroom count above 800.
  • Setbacks – Most cities have side yard and rear yard setbacks at 4’, but some cities allow 0’ setbacks, and some areas have fire department regulations that require 5’ setbacks – the bottom line is side and rear yard setbacks are much smaller now for ADUs.
  • Parking – Most cities want to see 1 off-street parking space on your property for the ADU, except when your home is located within ½ mile of public transit
  • Fire Sprinklers are required if the Main house has them or if ADU is not close to a fire hydrant.
  • Multifamily properties are allowed multiple ADUs
  • Solar panels are not required for prefabricated ADUs but may be required on a site-built ADU
  • Condo your ADU—This is a new State of California law, and if/when adopted by cities, you will be allowed to sell your ADU as a separate unit.


San Bernardino County ADU Regulations Are Some Of The Most Progressive In The State Of California!

  • San Bernardino County, CA, has a population of 209,924
  • Median property value: $ 286,200
  • Single-family properties: 41,352
  • Persons per household: 3.47
  • Median rental value: $ 1,589
  • Multi-family properties: 20,118

Based on San Bernardino County’s population, the number of Single-Family Homes, Multifamily Properties and Rental Value, there is a lot of opportunity for ADU construction in San Bernardino County.

San Bernardino County ADU Regulations
San Bernardino County ADU Handout


What is Prefabricated Construction?

  • Prefabricated construction means homes are built off-site in a factory, just like your car and most of every other item you use daily.
  • Prefabricated Homes are also known as Manufactured Homes and Modular Homes. Prefabricated Home plans are pre-approved by the State of California.
  • These homes are designed, reviewed, approved and inspected by the State of California.
  • The main benefits of prefabricated ADU homes in San Bernardino County, CA, are that they are less costly, faster to build in factories, and less impactful on homeowners and neighbors.


FAQ About ADUs in San Bernardino County, CA

Here are the answers to common questions that San Bernardino County homeowners ask when considering adding an accessory dwelling unit (ADU) to their property.


Does San Bernardino County Zoning Allow ADUs In My Neighborhood?

In 2020 and 2021, new laws were passed, making it easier for Californians to build ADUs. Major changes to San Bernardino County zoning regulations, permit requirements, and developmental standards went into effect, making it easier, faster and cheaper to build an ADU on your property.


How Many ADUs Can San Bernardino County Homeowners Build on Their Property?

San Bernardino County ADU rules allow one detached ADU and one junior ADU (a unit no more than 500 square feet located within the home) to be built on most single-family residential lots. If you live on a multifamily lot, you may be able to build two detached ADUs.


How Does USMODULAR Build ADUs?

We are prefabricated construction specialists. Our ADUs are built in a factory to ANSI – American National Building code (Tiny Homes), Federal/HUD building code (Manufactured Home) or CBC/Local Building code. We choose to build prefabricated construction as we have more control over the line and quality of construction. Also, prefabricated construction is less disruptive to residents of homes and neighborhoods as our time on site is minimal.


How Long Does Permitting an ADU Take in San Bernardino County?

We recommend ordering your home while we are still in the permit phase to shorten the overall built time. Typically, the timeline is 6-9 months to complete permits and build your ADU.

Here’s a snapshot of our process:

  • Free Virtual Site Assessment
  • Site Assessment, Meeting and Budget Prep
  • Design /Options finalized
  • Contract Signed
  • Plans – complete and submit – to the local building department
  • ADU Sales Order Finalized – Escrow opened
  • ADU fabrication
  • Permits issued
  • Site Construction begins – Foundation and Utilities
  • ADU delivery and Installation
  • Final Inspection
  • House Warming Party!!!!


According to San Bernardino County ADU Regulations, is a Parking Space Needed?

According to new state laws, an additional parking spot is not needed if the ADU is located within a half mile of a public bus stop or rail station, is on a street that requires on-street parking permits, but the permit has not been offered to the occupant of the ADU; or is located within one block of a public car-share program. If you do not meet this requirement – we will need to show space on your lot for ADU parking, and this can be on the existing driveway as a tandem space.


Are There Any Hidden Or Surprise Costs To Building An ADU In San Bernardino County?

We offer all-inclusive pricing for standard ADU sites. If your lot has special circumstances (hillside, sewer pumps, septic, crane, etc.), we will discuss any additional charges for extra site work, upgrades, etc., with you upfront so you know your full cost to build an ADU in San Bernardino County.


How Will An ADU Affect The Sale Price Of My San Bernardino County Home?

An ADU can increase property value and boost the primary home’s price when it’s time to sell. However, many factors go into home prices, and every case is unique.


How Do I Know If An ADU Can Fit On My Property In San Bernardino County?

Many properties can accommodate an ADU, and we offer ADUs ranging from 160 sq ft to 1,200 sq ft. Contact us for a free Virtual site assessment to determine if the property can fit an ADU.


How Does An ADU Access Sewer, Water And Electricity Lines?

In most cities, ADUs are allowed to connect to the primary home’s water, sewer, electricity and gas.


Can I Build An ADU On A Hillside In San Bernardino County?

Cities often have special building regulations for hillside construction, and the feasibility of this type of construction must be determined on a case-by-case basis.


Can I Customize the standard floor plan options?

Many of our ADU floorplans can be customized. You can pick colors, flooring, cabinets, and countertops to create a unique home.


Does It Make Sense For Me To Build An ADU On My Property?

That is a question only you can answer, but we can provide a few reasons why it might be:

  • You need extra space for aging parents or kids, and it’s expensive for them to live in an apartment
  • You want extra income and have unused space on your property.
  • For example, in many areas of Southern California, a 2- or 3-bedroom apartment costs $2000 per month. If you finance a $200,000 ADU with a home refinance and use your home’s equity, the typical monthly payments on this loan are $900-$1000. Economically, this seems to make sense, as it can save family members on rent or help you earn money every month.


What is a Junior Accessory Dwelling Unit (JADU)?

A Junior Accessory Dwelling Unit (JADU) in San Bernardino County is a dwelling unit with independent exterior access that is no more than 500 square feet in size and contained entirely within a single-family residence, including an attached garage. The proposed JADU or the existing single-family residence must be owner-occupied.


USModular Inc. is a premier contractor of prefabricated homes and ADUs in Southern California with over 40 years of experience in the industry. You can see the available floor plans and pricing at
Toll-Free: (888) 987-6638
Local: (951) 679-9907 Ext. 1

Check out our latest ADU projects!

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