ADU Questions, Answered Straight
Most homeowners come to us with the same handful of questions: what an ADU actually costs, how long permits take, whether a prefab unit is really cheaper than site-built, and whether their lot can even hold one. This page collects the answers we give every day at Orange ADU Builders, grouped so you can find yours fast. If you’d rather just talk it through, our line is open and estimates are free.
We’re an ADU-dedicated company, not a general contractor with a side business in backyard units. That focus shapes every answer below, because the tradeoffs between a Boxabl studio, a Mighty Buildings panelized unit, and a fully custom site-built ADU are real, and they change what you’ll pay and how long you’ll wait.
Key Takeaways
- ADU costs in and around Orange range from roughly $90,000 for a simple prefab studio to $400,000+ for a large custom detached unit with high-end finishes.
- Prefab brands like Abodu, Cover, and Boxabl can shorten the build phase considerably, but site work, permits, and utility tie-ins still take months.
- We handle design, permitting, and construction coordination, including garage conversions, attached units, and new detached ADUs.
- We’re licensed and insured, we offer free estimates, and we work with James Hardie exteriors for durability that lasts decades.
For a broader look at how we approach projects start to finish, see our ADU Builders in Orange page, or start at our home page.
Pricing & Estimates
How much does an ADU cost?
An ADU typically costs between $90,000 and $400,000+ depending on size, type, and finish level. A prefab studio from a brand like Boxabl sits at the low end, while a large custom detached unit with a full kitchen and high-end finishes lands at the top. The single biggest cost drivers are square footage, foundation and utility work, and whether you choose a turnkey prefab system or site-built construction.
| ADU Type | Typical Cost Range | Notes |
|---|---|---|
| Prefab studio (e.g. Boxabl) | $90,000 – $150,000 | Compact footprint, fastest path to occupancy |
| Garage conversion | $100,000 – $180,000 | Uses existing structure, saves on foundation |
| Junior ADU / interior conversion | $80,000 – $140,000 | Within existing home footprint |
| Panelized prefab (e.g. Cover, Mighty Buildings) | $150,000 – $280,000 | Fast assembly, modern finishes |
| Premium prefab (e.g. Abodu, Dvele, Plant Prefab) | $200,000 – $350,000 | Higher-spec systems and finishes |
| Custom site-built detached ADU | $250,000 – $400,000+ | Full design flexibility, highest finish ceiling |
Those ranges are honest market figures, not teaser pricing. Site work, utility trenching, and permit fees vary by lot, so the only way to get a real number is a site assessment. Call (877) 265-5812 for a free estimate, and we’ll walk your lot and give you a written range.
Do you offer free estimates?
Yes, we offer free estimates on every ADU project. We’ll review your lot, talk through which ADU types fit your goals and budget, and give you a written estimate with no obligation. That first conversation usually surfaces things you hadn’t considered, like utility routing or setback constraints, so it’s worth having early.
Is it cheaper to build a prefab ADU or a site-built one?
Prefab is often cheaper and faster on the build phase, but site-built gives you more design flexibility and can be the better value on an irregular lot. A prefab unit from Cover or Mighty Buildings arrives largely assembled, cutting on-site labor. Site-built construction costs more per square foot in many cases but lets you fit the unit precisely to your property and finish it however you like. We work across both paths, including Tuff Shed-style structures at the budget end, so we can compare them honestly for your situation.
What payment methods do you accept?
We accept standard payment methods including check, bank transfer, and major credit cards, and we structure payments in milestone-based draws tied to project progress. You’ll see the full payment schedule in your contract before any work begins. If you’re financing the project, we’re happy to talk through how draws typically align with lender disbursements.
Are there financing options for an ADU?
Yes, most homeowners finance ADUs through home equity lines, cash-out refinancing, or dedicated ADU construction loans. Because an ADU adds a rentable unit to your property, some lenders treat it more favorably than a standard renovation. We don’t originate loans, but we can provide the project documentation lenders ask for during underwriting.
Service & Scheduling
How fast can you respond?
We respond to new inquiries within one business day, and often the same day. For homeowners actively comparing builders, we can usually schedule a site visit within a week. ADU projects are planned months in advance rather than rushed, so the real timeline question is usually about permits and construction, not our callback speed.
Do you offer emergency ADU service?
No, we don’t offer emergency service, because ADU construction is a planned project rather than an urgent repair. If you have an active leak or structural issue during a build, contact your project manager directly and we’ll address it promptly. For routine questions between scheduled visits, one call or email is enough.
How long does it take to build an ADU?
A typical ADU takes 8 to 14 months from first design meeting to move-in, with permitting often consuming the largest share of that time. Prefab units can compress the construction phase to a matter of weeks once the foundation and utilities are ready, but the site work and approvals still run on the jurisdiction’s schedule. Site-built units take longer to construct but offer more design freedom.
What does the build process look like?
The process runs in a predictable sequence, and knowing it up front keeps surprises to a minimum. Here’s how a typical project moves:
- Site assessment and feasibility review. We check your lot’s setbacks, access, and utility capacity, then recommend ADU types that actually fit.
- Design and brand selection. We compare prefab options (Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab) against site-built, so you choose based on your lot, budget, and timeline.
- Permit submission and approvals. We prepare and submit plans, then track the jurisdiction’s review through to approval.
- Site work and foundation. Grading, foundation, and utility trenching happen before any unit arrives or framing begins.
- Construction or installation. Prefab units are set and tied in; site-built units are framed, roofed, and finished on site.
- Finishes and final inspection. James Hardie siding, interior finishes, and final sign-off complete the project.
If you also want your main house updated, we can coordinate kitchen and bathroom remodeling alongside the ADU so both projects share a schedule instead of competing for crews.
Do you handle ADU design and permitting?
Yes, we handle design and permitting as part of the project. We prepare plans that fit your chosen ADU type, submit them for review, and manage the approval process through to permit issuance. Because we work exclusively on ADUs, we know the plan details reviewers scrutinize and can head off common corrections before they slow you down.
Licensing & Trust
Are you licensed and insured?
Yes, Orange ADU Builders is licensed and insured. We carry the coverage a project of this scale requires, and we’re happy to walk you through our credentials during your estimate. You should ask any builder you consider for the same documentation before signing.
Do you guarantee your work?
Yes, we stand behind our work with a written workmanship guarantee, and our projects also carry the manufacturer warranties that come with prefab systems and materials. If you choose a panelized system from Mighty Buildings or a unit from Abodu, for example, those brands’ structural warranties apply alongside our own workmanship coverage. We spell out exactly what’s covered in your contract.
Who actually builds my ADU – your crew or the manufacturer?
It depends on the path you choose. With prefab systems, the manufacturer builds the unit in a factory and our team handles the site work, foundation, utility tie-ins, and installation. With site-built construction, our crews build on your property. Either way, you have one point of contact for the whole project, which is one of the reasons we work across multiple brands rather than locking into a single system.
How do I compare prefab brands fairly?
Compare brands on four things: delivered cost including site work, lead time, finish quality, and how well the unit’s dimensions fit your lot. A brand that looks affordable on its website may carry site-work costs that erase the savings. We work with six leading prefab brands, which means we can lay the options side by side and tell you where each one wins and where it doesn’t.
Why work with an ADU-dedicated builder instead of a general contractor?
An ADU-dedicated builder spends every day on permits, setbacks, utility tie-ins, and unit design, so that knowledge doesn’t get split across roofing, decks, and remodels. We see how the tradeoffs between prefab and site-built play out in real projects, and we can recommend the path that fits your lot instead of the one we happen to build. If your main house needs updates, we fold kitchen and bathroom remodeling into the same schedule.
Specific Services
Do you handle garage conversion ADUs?
Yes, we build garage conversion ADUs, which are often the most cost-effective path because the foundation and shell already exist. The work typically involves reinforcing the structure, upgrading insulation and utilities, adding a kitchen and bath, and installing new exterior finishes. Conversions also free you from building a new footprint, which keeps site costs down.
Do you handle new detached ADUs?
Yes, we build new detached ADUs, both prefab and site-built. A detached unit gives you the most design freedom and the best privacy for renters or family members. Whether a panelized system or a fully custom build suits you depends on your lot and budget, and we’ll compare both for you.
Do you handle junior ADUs and interior conversions?
Yes, we handle junior ADUs and interior conversions, which use existing space inside your home rather than a new structure. A junior ADU typically includes its own entrance, kitchenette, and bath within the home’s footprint. These projects are often the fastest and least expensive route to adding separate living space.
Can you also remodel our kitchen or bathroom?
Yes, we offer kitchen remodeling and bathroom remodeling alongside ADU construction. Many homeowners use an ADU project as the moment to update the main house, and coordinating both through one team keeps schedules aligned and avoids the juggling that comes with separate contractors. It’s a practical way to bring the whole property up together.
What materials do you use on the exterior?
We use James Hardie fiber-cement siding on ADU and main-house exteriors because it resists fire, holds paint longer, and stands up to decades of weather. An ADU is a long-term investment, and the exterior is what takes the beating, so the finish matters as much as the framing. James Hardie is the standard we rely on for durability and low maintenance.
Do you work with Tuff Shed-style structures?
Yes, we’re familiar with Tuff Shed structures and can advise on where they fit into the ADU picture. They serve the budget-conscious end of the range, though converting one to a fully permitted ADU involves utilities, insulation, and code compliance work. We’ll tell you honestly when a Tuff Shed-based path makes sense and when a different option gives you more for the money.
Service Area
What areas do you serve?
We serve Orange and the surrounding communities. Because ADU rules vary by jurisdiction, our team stays current on the local requirements that affect your project, from setbacks to utility connections. When you call, we’ll confirm whether your address falls in our service area and answer any jurisdiction-specific questions.
Can you build on a small or irregular lot?
Often yes, and the right ADU type depends on the lot’s shape and setback constraints. Smaller footprints, garage conversions, and compact prefab units frequently work where a large detached structure wouldn’t. A site assessment is the fastest way to know what’s possible, and we do those at no cost.
Ready to Compare Your Options?
You don’t have to sort through prefab brands, permit timelines, and lot constraints alone. We work across Abodu, Cover, Dvele, Mighty Buildings, Boxabl, and Plant Prefab, plus Tuff Shed structures and fully custom site-built units, so you get a straight comparison instead of a single vendor’s pitch. Whether you’re planning a garage conversion, a detached unit, or a junior ADU, we’ll help you choose the one that fits your property, budget, and timeline. Call Orange ADU Builders at (877) 265-5812 for a free estimate and honest answers about what your lot can hold.
Have a question we didn’t cover? Call Orange ADU Builders at (877) 265-5812.