Carlsbad ADU Regulations & Zoning

ADU in Carlsbad, CA


Want to learn about ADU regulations in Carlsbad, California? According to local laws, 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 a great summary can be seen in the ADU handbook published by the State of California.

One of the most affordable types of ADUs is a prefabricated home. One of Carlsbad’s most active prefabricated ADU builders in Carlsbad 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.
  • Local homeowners can also build one attached ADU or one detached ADU and one JADU, all on the same property.
  • California 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 there are some cities that 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 the 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 id/when adopted by cities – you will be allowed to sell your ADU as a separate unit.


The City of Carlsbad ADU regulations are some of the most progressive in the State of California!

  • Carlsbad, CA, has a population of 105,328
  • Median property value: $ 811,900
  • Single-family properties: 32,780
  • Persons per household: 2.6
  • Median rental value: $ 3,332
  • Multi-family properties: 12,818

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

Review City of Carlsbad ADU Regulations


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. The State of California pre-approves prefabricated home plans.
  • These homes are designed, reviewed, approved and inspected by the State of California.
  • The main benefits of Prefabricated Homes are they are less costly, faster to build in factories and have less impact on homeowners and neighbors.


Examples of allowable ADU sizes in Carlsbad are provided below:

Square Footage of Existing single-family residence (SFD) Maximum Allowed Square Footage for Detached ADU Maximum Allowed Square Footage for Attached ADU (up to 50% of SFD)
1,450 sq. ft. 1,200 sq. ft. 725 sq. ft.
1,800 sq. ft. 1,200 sq. ft. 900 sq. ft.
2,000 sq. ft. 1,200 sq. ft. 1000 sq. ft.
3,000 sq. ft. 1,200 sq. ft. 1,200 sq. ft.
4,500 sq. ft. 1,200 sq. ft. 1,200 sq. ft.


Why Build an Accessory Dwelling Unit in Carlsbad?

People build ADUs for many reasons, but the most common are rental income and/or to house relatives. Having a second unit is a simple and old idea to convert unused space. Second units are a relatively affordable type of construction because they do not require purchasing land or major new infrastructure. Here are some of the reasons to build an accessory dwelling unit.

Rental Income:  Many homeowners build accessory dwelling units to help pay the mortgage because they offer a steady source of income.

California passed Senate Bill 1069 to increase the supply of housing in the state. For this reason, any accessory dwelling unit may be used for a long-term rental.

What would you do with an additional $20,000-40,000 a year?
Average Rent per Month:
San Francisco: $3,800
San Diego: $2,000
Los Angeles: $2,200
Portland: $1,900
Austin: $1,700

Rental Estimate Income-Above data based on local average property data and value

Appreciation Estimate = (Base Value: $800,000) / (Home’s Living Space: 1,350 sqft) * (ADU’s Living Space: 500 sqft)
Rental Estimate = (Rent Per Sqft: $4.79) * (ADU’s Living Space: 500 sqft)

  • Housing for Relatives:  Accessory dwelling units allow homeowners with adult children, aging relatives or relatives with special needs to live together, but also maintain privacy
  • Downsizing:  Some homeowners build an ADU for themselves, often in retirement, while they rent the primary dwelling.
  • Flexible Space: A homeowner’s needs may change over time, and ADUs allow for flexibility and for the property to adapt to new needs, such as a growing family, live-in nanny or aging-in-place parents.
  • Sound Investment:   To maximize your return on investment those who build an ADU should plan to own their property for an extended period. The value passive rental income brings, especially in a city like Carlsbad, which boasts soaring rental prices is undeniable.
  • Community Benefits: ADU’s can help address the housing challenges in San Diego County by adding homes that are generally more affordable, which helps provide workforce housing and preserves diversity and community character. Many homeowners are motivated to build a second unit to rent to a school teacher, firefighter or other community member who might otherwise have to commute a long distance to find a home they can afford.


FAQs about ADUs in Carlsbad, CA

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

Are ADUs allowed in my neighborhood in Carlsbad, CA?

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

Can I build an ADU in Carlsbad? How many can I build?

On most single-family residential lots, you can build one detached ADU and one junior ADU (a unit no more than 500 square feet located within the home). If you live on a multifamily lot, you can 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 Carlsbad?

We recommend ordering your home while we are still in the permit phase to shorten the overall built time.

Are there any hidden or surprising costs to building an ADU in Carlsbad?

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

How will an ADU affect the sale price of my house?

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

Can I customize the standard floor plan options?

The Silver and Gold floor plans have limited options to change floor plans, but the units’ interior has some flexibility and upgrades available. ModPro series is a custom plan, and we can make changes to these plans and /or create a custom floor plan.

How do I know if an ADU can fit on my property in Carlsbad?

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 a 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 Carlsbad, CA?

Cities often have special building regulations for hillside construction. The feasibility of hillside construction must be determined on a case-by-case basis.

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:

  • 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 is $2000 per month. If you finance a $200,000 ADU with a home refinance and use your home’s equity – typical payments on this loan are $900-$1000 / month. Economically, it seems to make sense as it can save family members on rent or help you earn $ every month.

What is a Junior Accessory Dwelling Unit (JADU)?

A Junior Accessory Dwelling Unit (JADU) in Carlsbad 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 with over 40 years of experience in the industry. You can see the available floor plan and pricing at
Toll-Free: (888) 987-6638
Local: (951) 679-9907 Ext. 1

Check out our latest ADU projects!


US Modular

  • Enter your 10-digit phone number including area code. Use only numbers.
  • This field is for validation purposes and should be left unchanged.

Call Now Button