ADU / Accessory Dwelling Unit

Accessory Dwelling Units (“ADUs”) is a secondary dwelling unit with complete independent living facilities for one or more persons and generally takes three forms: detached from the primary residential structure, attached but separate, or repurposed existing space within the primary structure. ADUs are commonly known as granny flats, in-law units, backyard cottages, or secondary units.

ADUs create space for you and your community. Here are a few of the many benefits of an ADU:

1 ) ADUs are an affordable type of home to construct in California because they do not require paying for land, major new infrastructure, structured parking, or elevators.

2 ) ADUs can provide a source of income for homeowners.

3 ) ADUs are built with cost-effective wood frame construction, which is significantly less costly than homes in new multifamily infill buildings.

4 ) ADUs allow extended families to be near one another while maintaining privacy.

5 ) ADUs can provide as much living space as many newly-built apartments and condominiums, and they’re suited well for couples, small families, friends, young people, and seniors.

6 ) ADUs give homeowners the flexibility to share independent living areas with family members and others, allowing seniors to age in place as they require more care.

Generally, your single-story ADU needs to be 4 feet away from the rear and sides of your property line, 10 feet away from your primary structure, and 15 feet away from the front of your property line. These setbacks can vary slightly jurisdiction by jurisdiction, so a tailored feasibility analysis needs to be done. Begin that process with us now by briefly describing why you are considering an ADU. We can do an initial assessment of whether or not an ADU can fit in your backyard over Zoom. If that goes well, we’ll do an on-site in-depth feasibility study.

Factory-Built ADU

On-site construction is generally slower and more expensive. According to some studies, off-site modular manufacturing like we do at Halsell Builders enables construction to be completed in half the time and at up to a 30% cost savings.

An efficient construction process that achieves its budget and deadline requires a boots-on-the-ground understanding of local jurisdictions. At Halsell Builders, we are builders first with decades of experience successfully navigating and optimizing the construction process in the specific geographies we are currently serving. By drastically shortening the permitting process and build time, we reduce the cost to build, which we pass on to you as cost and time savings.

We also build California Building Code Compliant, fully mortgage-able, seismic- and thermal-compliant, hyper-efficient, and elegant housing that's delivered within 6-7 months of contract signing at an attractive under-market price point.

Yes. We can deliver up to 10 ADUs at once. An added benefit of ordering multiple ADUs is that you have greater ability to customize your ADUs.

We can guarantee delivery of your finished product 3 months after permitting is completed. On average, from the day you complete your initial feasibility study with Halsell Builders to installing your unit is 6-7 months. This is significantly shorter than the 12-18 months for an average ADU built on-site.

The actual construction of the ADU is approximately 5-22 working days.


Yes, 2 kinds of permits are required by every jurisdiction: a permit for the vertical structure and a permit for the site work. With prefabricated modular construction like we do at Halsell Builders, the permit for the vertical construction portion can be outsourced to a private 3rd party entity that's subject to state regulation under the California Department of Housing and Community Development, thereby bypassing local requirements. The site work will still be subject to local permitting regulations. As Halsell Builders scales and grows its ADU program, there will be more standing permits in each county and city which allows for faster turn times and potentially cheaper permits.

Our permitting process for the vertical component is 5-10 business days which is done through the California Department of Housing and Community Development. The site work permit is still subject to local jurisdictions. In Santa Barbara and San Luis Obispo County, site work permits generally take 10-12 weeks. However, our offsite construction process allows us to continue the construction of your ADU while awaiting the permits.

The permitting for vertical construction is $3,500 to $5,000 depending on your jurisdiction.


Once your ADU has been built in the facility in Northern California, we will transport it to your desired location. On site, we’ll use a hydraulic truck crane to set your ADU onto the foundation. We will finish the hookups and other final on-site work needed to get the unit up and running.

Yes! In Santa Barbara and San Luis Obispo County, we personally complete the site work so you don’t have to do anything yourself or find any other contractors to help.


Yes. We offer color customizations, roofing customizations and upgraded finishes.

Funding Your ADU

There are several ways to finance your ADU, including our ‘no money down’ option. Please contact James Halsell, for details.

No. We split the total payment into 5 scheduled payments over ~150 days.