ADU Questions, Answered Straight
Most homeowners come to us with the same core question: can I actually build an ADU on my property, and what will it take? The short answer is that Brea allows ADUs on most single-family lots, and the path depends on your lot, your budget, and which build method fits. This page covers pricing, permitting, timelines, licensing, and the specific ADU types we build in Brea. If your question isn’t here, call us at (866) 251-7857.
We’re Foundry ADU Builders. Every service we offer is oriented around accessory dwelling units, from factory-built modular units to traditional site-built construction to the kitchen and bathroom work that makes a unit livable. That focus means we answer these questions every week, not once a quarter.
Key Takeaways
- ADU costs in Brea vary widely by type and method: garage conversions and junior ADUs sit at the lower end, detached new construction at the higher end.
- We build across the full spectrum of methods: prefab (Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab), Tuff Shed conversions, and conventional site-built.
- We handle design, permitting, construction, and interior finish under one contractor relationship.
- Free estimates, transparent line-item pricing, and a single point of contact from first call to final walkthrough.
Pricing & Estimates
How much does an ADU cost in Brea?
ADU costs in Brea generally run from the low five figures for a garage conversion up to the mid-to-high six figures for a fully detached, site-built unit, depending on size, finishes, and site conditions. The number that matters is your number, and it depends on four things: ADU type, square footage, build method, and your lot’s existing utilities and access.
Rather than quote a single “average,” we build a line-item estimate for your specific property. Prefab and modular units often come in lower on labor because the shell is factory-built, while site-built gives you more freedom on layout and finish. We’ll walk you through both and show you where each one lands for your lot.
What does each ADU type typically cost?
Here’s how the major ADU paths break down on cost, from lowest to highest:
- Junior ADU (JADU): A converted space within your existing home, usually under 500 square feet. Lowest entry point since it uses existing walls and often existing plumbing.
- Garage conversion ADU: Converting an existing garage. Moderate cost, faster permits in most cases, and no new foundation or roof.
- Tuff Shed conversion: A budget-conscious path using a pre-built structure finished to livability standards. Good for homeowners who want speed and simplicity.
- Prefab / modular ADU (Abodu, Cover, Boxabl, Mighty Buildings, Dvele, Plant Prefab): Factory-built shell, delivered and set. Cost depends heavily on brand, size, and site prep.
- Detached site-built ADU: Highest cost, highest customization. Full foundation, framing, utilities, and finishes built on your lot.
Every one of these includes design and permitting work, which we coordinate. For an exact line-item breakdown on your property, call (866) 251-7857. Estimates are free.
Do you offer free estimates?
Yes, we offer free estimates on all ADU projects in Brea. We’ll review your lot, discuss your goals, and give you a written estimate with line items so you can see exactly where the money goes. There’s no charge and no obligation.
We also walk you through the trade-offs between build methods during that visit, because the estimate only means something if you understand what you’re comparing. Call (866) 251-7857 to schedule.
Is it cheaper to convert my garage or build a new detached ADU?
Converting your garage is almost always cheaper than building detached, because you’re reusing the foundation, roof, and often the utility connections. A detached ADU requires new site work, a new foundation, and new utility runs, which push the cost up.
That said, garage conversion gives up your parking and storage, and detached gives you a fully separate structure with its own entrance and yard space. The right call depends on how you plan to use the unit. We’ll lay out both numbers side by side so the decision is straightforward.
Service & Scheduling
Do you offer emergency ADU service?
We don’t offer emergency call-out service, because ADU construction is planned work rather than an emergency trade. What we do offer is responsive scheduling: when you call, you get a real conversation about your project and a clear next step, not a runaround.
If you have an urgent issue on an existing ADU (a leak, a failed fixture, a utility problem), call us anyway. We’ll tell you honestly whether it’s something we can address and how soon. Reach us at (866) 251-7857.
How fast can you respond?
We respond to new ADU inquiries quickly, usually within one business day, and we schedule site visits around your availability. The design and permitting phase that follows depends on your jurisdiction and the ADU type, not on us alone.
Once permits are in hand, prefab and modular units can compress the build timeline significantly compared to conventional site construction, since the shell is manufactured off-site. We’ll give you a realistic schedule at the estimate stage rather than an optimistic one.
How long does an ADU project take from start to finish?
Most ADU projects in Brea take several months from signed contract to finished unit, with the split depending on method. Prefab and modular paths can move faster on construction because the shell arrives built; site-built takes longer on framing and finish work.
Permitting is often the longest single phase and varies by jurisdiction, which is why we handle it for you. Here’s the general sequence we follow:
- Site visit and feasibility review: We look at your lot, setbacks, utilities, and access, and confirm which ADU types fit.
- Build-method selection: We match you to the right path, whether that’s a prefab brand, a Tuff Shed conversion, a garage conversion, or site-built.
- Design and permitting: We coordinate drawings and submit for permits with the applicable jurisdiction.
- Site prep and foundation or delivery: Depending on method, we either prepare the site for factory delivery or begin on-site construction.
- Interior finish: Kitchen, bathroom, flooring, and final details, done by our in-house team so there’s no handoff to a second contractor.
- Final walkthrough: We walk the finished unit with you and address any punch-list items.
Licensing & Trust
Are you licensed and insured?
Yes, we’re a licensed and insured ADU contractor. We’re happy to provide our license and insurance details during the estimate process so you can verify them before signing anything.
We don’t publish policy numbers on this page, but we’ll share documentation directly. Any contractor you hire for an ADU in Brea should be able to do the same.
Do you guarantee your work?
Yes, we stand behind our work and address any issues that arise after completion. The details of what’s covered and for how long are spelled out in your contract so there’s no ambiguity later.
We also use durable materials, including James Hardie fiber cement products for exterior cladding on site-built work, because long-term performance on an ADU structure depends on the exterior holding up. That’s part of how we reduce callbacks in the first place.
What payment methods do you accept?
We accept standard payment methods including check, bank transfer, and major credit cards, and we structure payments around project milestones rather than asking for large sums upfront. Your contract will lay out the schedule clearly.
If you have a specific payment arrangement in mind, bring it up during the estimate and we’ll work through it. Call (866) 251-7857 to start that conversation.
What areas do you serve?
We serve Brea and the surrounding Orange County and Los Angeles County communities. If you’re unsure whether your address is in our service area, call us and we’ll tell you directly.
Brea’s lots vary quite a bit by neighborhood, and that affects which ADU types are practical. We’ll factor your specific property into the feasibility review rather than giving you a generic answer. You can also see our work and service area on our home page, and if you’re nearby in La Habra, our ADU Builders in La Habra page covers that area in detail.
Design, Permitting & Project Scope
Do you handle ADU design and permitting?
Yes, we handle design coordination and permitting as part of the project. We prepare the drawings needed for submittal, work with the applicable jurisdiction through plan check, and manage the back-and-forth that permitting often involves.
Permitting is where a lot of ADU projects stall when homeowners try to manage it themselves. Having one contractor own that phase keeps the project moving and keeps you out of the middle of it.
Do you handle garage conversion ADUs?
Yes, we build garage conversion ADUs. It’s one of the most cost-effective ADU paths because the foundation, roof, and often the utilities are already in place.
We handle everything from the structural work to the interior finish, including the kitchen and bathroom that make the converted space livable. If you’re weighing a conversion against a detached unit, we’ll show you the cost difference for your specific garage.
Do you handle new detached ADUs?
Yes, we build new detached ADUs, both site-built and prefab. For site-built, we handle foundation, framing, utilities, exterior cladding, and interior finish. For prefab, we work with the brand to coordinate delivery and site prep, then finish the interior.
Detached ADUs give you the most flexibility on layout and the most privacy for tenants or family members. They’re also the highest-cost path, so we make sure the design and budget line up before anything gets built.
Do you handle junior ADUs and interior conversions?
Yes, we handle junior ADUs (JADUs) and interior conversions. A JADU is a smaller unit created within your existing home’s footprint, usually under 500 square feet, and it’s the lowest-cost ADU path available.
These projects often involve adding or upgrading a kitchenette and bathroom within the converted space, which is exactly the kind of interior work we do in-house. It’s a practical option for homeowners who want rental income or a space for a family member without building a new structure.
Which prefab and modular brands do you work with?
We work with Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab, and Tuff Shed. That range lets us match the build method to your lot, budget, and timeline rather than pushing a single product.
Each brand delivers something different. Abodu and Cover lean design-forward. Mighty Buildings and Boxabl bring factory-built modular technology that can compress build timelines. Dvele and Plant Prefab offer higher-end prefab construction. Tuff Shed gives budget-conscious homeowners a path to a livable ADU that still meets standards.
We’ll explain what each brand actually delivers and where the trade-offs are, then recommend based on your property. Prefab, modular, or site-built: we build across the full spectrum.
Can you finish the interior of my ADU if another company built the shell?
In many cases, yes. We do kitchen remodeling and bathroom remodeling, typically in the context of completing ADU interiors, and we can step in on a shell that’s already built.
We’ll assess what’s been done and what’s left before committing to a scope. If it’s workable, you get one contractor from shell to finished living space, without a second handoff. Call (866) 251-7857 to discuss your situation.
What exterior materials do you use?
We use James Hardie fiber cement products for exterior cladding on site-built work, chosen for durability and weather resistance. Fiber cement holds up well over time and needs less maintenance than some alternatives.
For prefab and modular units, the exterior finish depends on the brand and model. We’ll tell you what each one uses so you’re comparing like with like.
Making the Decision
How do I know which ADU type is right for my Brea property?
The right ADU type depends on your lot’s size and setbacks, your budget, how you plan to use the unit, and whether you want to keep your garage. That’s what the feasibility review is for.
We look at all of it during the site visit: available space, utility access, access for delivery or construction, and the setback requirements that apply. Then we match the build method to your lot, budget, and timeline, not the other way around.
Can I use my ADU for rental income?
Yes, many Brea homeowners build ADUs specifically for rental income, and an ADU can add a rentable unit to your property without buying another parcel. Whether and how you can rent it depends on local rules, which have shifted in recent years to make ADU rentals more feasible.
We’ll point you to the current regulations during the feasibility review so you’re planning with accurate information, not assumptions.
What’s the first step?
The first step is a free estimate and feasibility review at your property. We’ll look at your lot, talk through your goals, and give you a written estimate with the build methods that fit.
There’s no charge and no pressure. Call Foundry ADU Builders at (866) 251-7857 to schedule. We’ll match the build method to your lot, budget, and timeline, and we’ll tell you honestly where the trade-offs are.
Contact Us
If you’re ready to stop weighing options and get a real number for your Brea property, call Foundry ADU Builders at (866) 251-7857 for a free estimate. We’ll walk your lot, explain which build methods fit, and give you a line-item estimate you can actually compare. One contractor from foundation to finished kitchen, whether that’s prefab, modular, or site-built.
Have a question we didn’t cover? Call Foundry ADU Builders at (866) 251-7857.