What a full detached ADU build covers

When you hire us for a detached ADU build, we handle everything from the first shovel in the ground to the final inspection. That typically includes:

Site prep and foundation

• Demo and site clearing (as needed)

• Grading and drainage

• Utility trenching

• Foundation excavation, rebar, forms, and concrete pour, handled in-house through our sister company Supreme Concrete Group

Structural construction

• Framing

• Roofing

• Exterior siding and finishes

• Windows and doors

Mechanical systems

• Electrical rough-in and finish

• Plumbing rough-in and finish

• HVAC (if included in your plans)

Interior finishes

• Insulation and drywall

• Flooring, cabinets, countertops, trim, paint

• Fixtures and appliances (per your plans and selections)

Permitting and inspections

• Coordinating plan submittal with the city or county

• Managing inspections through the build

• Final walkthrough and certificate of occupancy

If you'd rather handle the interior finishes yourself to save on labor, see our ADU Shell Builds service. If you only need foundation work, we offer that separately through Concrete ADU Foundations. For the full menu of options, see all our ADU services.

Who this service fits best

A full detached ADU build is the right fit if:

• You want a complete backyard home, not a renovation or conversion. We do ground-up new construction only.

• You have backyard space that can accommodate a detached structure within your city's setback rules. Not sure? We can walk your property and tell you honestly.

• You'd rather have one builder handle the whole project than juggle multiple contractors yourself.

• You value quality and honest communication over the absolute lowest bid. We're competitive on price, but we're not the cheapest quote you'll get, and we're upfront about why.

• You want the owner personally involved in your build, not a project coordinator you've never met.

This service isn't the right fit if: you want an attached ADU, a JADU, or a garage conversion. We don't do those.

What sets TrueBuild apart on detached ADU builds

Foundations poured in-house
Most ADU builders subcontract their foundation work to whoever's available. We don't. Our sister company, Supreme Concrete Group, handles every foundation we pour. For one of the most critical and expensive phases of the build, that's a real difference. Read more about our approach on our Concrete ADU Foundations page.

Jose runs every project personally
There's no sales team, no project coordinator layer, no "account manager" calling you from a call center. Jose Flores walks every property, signs every contract, and stays on the job through final inspection. You get the owner's phone number, not an extension.

No surprise change orders
We bid the job honestly up front instead of low-balling to win the project and padding it later with changes. When something genuinely does need to change mid-build, we explain why before the work starts, not on the final invoice.

Small on purpose
We deliberately limit how many projects we run at once. That's not a limitation, it's how we keep Jose personally involved in every build and how we maintain quality without needing layers of middle management to stay organized.

Popular detached backyard ADU layouts

Detached ADUs in California can typically be built up to 1,200 square feet, with 1–3 bedroom layouts being the most common. Some popular options homeowners ask about:

• Studio ADU plans: open-concept layouts, typically 400–600 sq ft

• 1 bedroom ADU plans: efficient backyard homes, often 500–800 sq ft

• 2 bedroom ADU plans: popular for rental income and multigenerational living

• 3 bedroom ADU plans: larger family-friendly layouts

• Two-story ADU plans: a good option when your lot is small

• Narrow ADU plans: layouts that work on tight or awkward lots

Don't see a layout that fits? We also build from customer-supplied plans (see our Build From Your Plans service) or we can coordinate plans through our Design-Build ADU service.

What to expect on timeline

Every ADU build is different, but a typical detached ADU project looks something like this:

1. Pre-construction (plans and permits): 2–6 months. Depends heavily on whether you already have approved plans, which city or county you're in, and how backed up the permit office is.

2. Construction: 4–6 months. A straightforward single-story detached ADU usually lands in this range, assuming no major site complications or plan revisions mid-build.

3. Final inspections and walkthrough: 2–4 weeks.

Things that can shift a timeline: complicated sites (hillsides, tight access, extensive site prep), plan revisions required during inspections, weather (especially winter storm runs in San Diego), and materials lead times on specific finishes.

If a builder quotes you a timeline significantly faster than this on a full detached build, be skeptical. Timelines that sound too good to be true usually are.

What affects detached ADU cost

Detached ADU pricing depends on the factors you'd expect: size, number of bedrooms and bathrooms, site complexity, utility connections, finish selections, and your local jurisdiction's permit fees.

We don't publish a fixed price per square foot because that number misleads more than it informs. A straightforward flat lot in Chula Vista will cost a lot less to build on than a hillside lot in La Jolla with long utility runs, even if the ADU itself is identical. Honest pricing requires actually looking at your property.

For an honest bid on your specific project, schedule a free consultation and we'll come walk the site with you.

Common questions about detached ADU builds

How big can a detached ADU be in California?
California state law generally allows detached ADUs up to 1,200 square feet, though local jurisdictions can set smaller limits in some cases. Most of the detached ADUs we build in San Diego and Riverside counties fall between 600 and 1,200 sq ft.

Do I need to live on the property to build a detached ADU?
No. California law removed the owner-occupancy requirement for ADUs permitted between 2020 and 2025, and as of 2025 owner-occupancy can't be required for most detached ADUs. This makes detached ADUs a strong option for rental income and investment properties.

Can I rent out my detached ADU?
Yes, with some restrictions on short-term rentals (under 30 days) depending on the jurisdiction. Long-term rentals are allowed in most San Diego County cities.

Do you build on hillside lots?
Yes. Hillside builds require more site prep, engineering, and often more extensive foundation work, all of which we can handle in-house through Supreme Concrete Group.

How far do you travel for a detached ADU build?
We serve all of San Diego County and Southwest Riverside County: Temecula, Murrieta, Menifee, Lake Elsinore, and Wildomar. For projects outside those areas, we can usually take a look but can't promise coverage.