ADU in San Diego | Learn From Prefab Accessory Dwelling Unit Builders in San Diego

Welcome to USModular Home Builders, Southern California’s premier full-service design and general contractor for the construction of your ADUs in San Diego. We have built countless ADU homes using prefab construction and are experienced and knowledgeable in dealing with all aspects of the building process.

With 75 combined years in general contracting and real estate development, we learned a few things along the way.

We handle all aspects of your project from the initial site visit to the creation of budget/contract through permits and construction, utility connections, and finally handing you a set of keys for your new modern prefab ADU…all with minimal disruption to residents of the primary dwelling unit as the ADU is set into your backyard in ONE DAY!!!!!

What is a San Diego ADU?

’Prefab’ is shorthand for ‘Previously Fabricated’, meaning it was built in a factory and is reassembled or finished onsite. Our prefab ADUs in San Diego are built to completion in our partner factories, transported to your site, and can be installed to a foundation within 24 hours. Prefab ADU construction in San Diego has the advantage of being significantly faster and more efficient than other construction types. Building in a factory allows us to use efficient processes and avoid weather delays so that we can complete your project on time and on schedule!

A prefabricated accessory dwelling unit (aka granny flat or companion unit) is a second small dwelling on the same parcel of land as your single-family house. A prefab home ADU can be up to 1,200 sq ft and can be built as:

Detached stand-alone building
Attached to a primary dwelling
Converted space within the primary dwelling (Junior ADU)

Why are ADUs becoming more popular in San Diego?

Thousands of new ADUs are being built in communities across the U.S. because they are a manageable and minimally disruptive option for adding needed housing to existing neighborhoods. Moreover, ADUs typically cost less than other forms of housing and make efficient use of existing land.

The other factor driving ADU adoption is that they serve so many varying needs that mirror socioeconomic trends in the U.S. ADUs allow for people to age in place or form multigenerational households to ease caregiving responsibilities and cost. Homeowners, given the high cost of buying a house, frequently turn to ADUs to provide additional income to make ends meet. Lastly, the appeal of downsizing and minimalist living seems to be growing, and ADUs allow people to simplify their lives and still live in a neighborhood setting.

Why Build a Prefab ADU in San Diego?

Additional Space for family members – grandparents, kids, and relatives

We recently built an ADU for a family in Orange County. It was built for the homeowner’s Mom, who was living in a 1 bedroom apartment – 10 miles from family, and they were spending $1,500 a month on rent. Grandma moved into The Bungalow ADU and is now closer to her daughter and grandkids. She feels safer, and has more social connections with family. The family has a net savings of over $1000 per month in rent. A true ADU success story.

Rental Income – turn a single-family rental property into a 2-income property.

An Investor with a single-family income property in San Diego put it best when he asked us – “where can I buy a 2-bedroom rental property for under $120,000 in San Diego? Nowhere! But I can build a 2 bedroom ADU for this price – it’s a no brainer”

The presence of an ADU can often enhance the attractiveness of a house on the market, and increasingly investments in new ADUs are being reflected in the appraised value of those properties.

What is the Cost of ADUs For Sale?

There are many local and site-specific factors to determine the complete cost to build an ADU, including access to the backyard, topography, utility location, sewer or septic, local fees, including sewer capacity fee, school fees, permits etc. But we have created the cost to build an ADU that assumes we have access to the backyard on a level lot and sewer is available within 100 ‘of the house. The starting cost for our 398 sq ft 1 bedroom ADU (Federal Building Code) is $78,000, which includes the ADU, transportation to the site, roll set/ installation on a permanent foundation, and connection to utilities. The local fees are city or county-specific and typically range from 5-15% of the quoted construction cost.

New 2024 San Diego Laws:

San Diego is in a housing crisis, both in physical houses and affordability. ADUs help the crisis by getting more homes and lowering the cost of building as land and utility infrastructure are already in place (2 of the biggest costs to build a new home).

New State of San Diego ADU laws include:

ADUs can be up to 1,200 sq. ft. regardless of the size of the primary dwelling unit (as long as you meet setbacks and FAR)
Setbacks reduced to 4’ side and rear yard
Parking requirement for ADU waived
No owner occupancy of primary dwelling unit (great for investors)
60-day review and approval process by the local building department or considered approved
Waiver of local development fees for ADUs less than 750 sq. ft.
Multifamily homes eligible for ADU
Fire Sprinklers are ONLY required if the Primary Dwelling Unit has them in place

Are ADUs allowed in my San Diego neighborhood?

In 2019, San Diego passed a series of bills to make it easier for homeowners to build ADUs. Major changes to zoning regulations, permit requirements and developmental standards went into effect on January 1st, 2020, superseding previously restrictive local regulations. While zoning, regulations and fees vary by municipality, the recent state laws say that ADUs can be built on property zoned for single-family and multi-family use.

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

If you live on a residential lot, yes! You can build one detached ADU and one junior ADU (a unit no more than 500 sq ft located within the home). If you live on a multi-family lot, a maximum of two detached ADUs are allowed on the property.

Why Hire Prefabricated ADU Builders In San Diego?

Our accessory dwelling unit builders in San Diego get asked this question daily. For us, it’s a pretty easy answer because we can build better, faster, greener and for less in a factory than a site-built ADU. It’s the same reason that we drive cars built in a factory: they have a more precise process building on a production line, indoors, by a team of workers that work in sync…than assembled in your backyard. Another important reason to consider prefabricated site construction is site construction time, as site-built projects will take months of daily hammering, sawing, dumpsters, and port-o-potties with 10+ different workers walking into the backyard during this time period. With prefabricated construction, the ADU is built in a factory, and we set the unit in the backyard in ONE DAY. Once the ADU is set, we have a very small crew to finish work and utility connections.

How Long Do USMODULAR ADU Contractors in San Diego Take To Build A Unit?

A lot depends on you. How long you take to choose the style, code and floor plan will determine the length of the project. Once the ADU plan is chosen and the contract is signed, it typically takes from 2-3 months to get a building permit and build a project. Much of this time is spent on the State and Local approval of the building plans. Once we have a permit in hand, our USModular San Diego ADU builders will act very fast and typically can complete a project within 1-3 months.

What is the process to build an ADU in San Diego with USModular?

Phase 1: Planning

Site visit to determine setbacks, accessibility, utility location /availability, FAR
ADU submittal requirements
New construction of ADU with Modular (CBC/Local) or Manufactured (HUD/Federal))
Develop a conceptual budget for ADU and site construction

Phase 2: Construction Contract

Finalize construction budget and contract

Phase 3: Plan Design and Submittal

Site plan design
ADU approval through State approved 3^rdparty and local jurisdiction
Build (Fabrication) the ADU at Factory while prepping onsite construction necessary to meet local ADU requirements, including utilities, foundation
Coordinate with the local building department for inspections

Phase 4: Final Inspection