Golden State ADUs is a full-service, design-build ADU builder serving Concord, California. We assess your property, design the living space, complete structural and civil engineering in-house, manage the City of Concord permit process and the separate outside-agency approvals, build, and carry the project through final inspection. One team, one point of accountability, from concept to completion.
Building permits for an accessory dwelling unit (ADU) inside Concord city limits are issued by the City of Concord Community Development Department, Building Division, at the Permit Center in Building D, 1950 Parkside Drive. California law strongly favors accessory dwelling units while still letting cities enforce local rules, size limitations, and design standards, which is why the right ADU builder matters more than a general contractor who subcontracts the design and hopes the pieces line up.
Licensed and bonded (LIS. #1125656). Every project carries a 10-year structural integrity warranty and a 1-year fit-and-finish warranty. Trusted by 100+ happy customers.
Book A Consultation. One 1-hour walkthrough will tell you whether your Concord property works.
Accessory Dwelling Unit (ADU) Construction Services in Concord
We handle every phase of your ADU project in-house, so you never hire a separate architect, engineer, or permit expediter. Granny flats, casitas, in-law suites: the names change, the permit path does not. A secondary housing unit can be detached, built as an attached ADU sharing a wall with your primary residence, or converted from existing space. Working with one ADU builder from first sketch to final inspection keeps the drawings, the engineering, and the field crew speaking the same language. The right answer depends on your lot, your budget, and your design goals. See our full ADU design, permitting and construction services.
Custom Design and In-House Engineering
Architectural design, structural engineering, and civil engineering come from Golden State Design & Engineering, our in-house design arm. That matters in Concord, where nonexempt ADUs generally have to be comparable to the primary dwelling in roof pitch, roof form, siding materials, and colors. A custom unit gives homeowners control over layout, light, materials, and privacy from the main living space, instead of a plan drawn for someone else’s property. Even a small space can carry its own kitchen, a full bathroom, and a separate entrance when the floor plan is built around how you actually live.
Detached ADU Construction
Detached ADUs are standalone structures with their own entrance and complete living space, from studios through three bedrooms. This is the configuration most often used to generate rental income, because the unit reads as its own small home. Square footage in Concord is generally capped at 1,000 on lots of 12,000 square feet or less, and 1,200 on larger lots. Height is generally capped at 16 feet, though Concord allows up to 18 feet in certain circumstances, including properties within one-half mile of a BART station or Clayton Road. Those size limitations are ceilings, not recommendations, and the right square footage is the one your lot and your budget both support.
Garage Conversions and Converted Living Space
Converting an existing garage is one of the most popular paths in Concord. An existing basement area or other permitted space can also become a legal rental unit, a home office for a small business, or quarters for a parent. Basement apartments are less common here than garage conversions, but we evaluate both. Conversion work still has to satisfy local building codes for ceiling height, egress, fire separation, insulation, and ventilation, and ADU construction typically runs two to four months once permits are in hand, since the basic structure already exists.
Permitting and Agency Coordination, Done For You
Permits, paperwork, compliance, done for you. We prepare and submit the City of Concord building permit package, then handle the approvals the City does not automatically route. Concord’s pre-approved-plan checklist requires separate fire-district and water-district approval for detached ADUs plus school-district certification. Utility connections are screened before design is finalized, every project complies with current code, and plan corrections are ours to answer, not yours.
Retirement and Multigenerational ADUs
Single-level, accessible living space for aging parents or adult children who want independence without distance. Zero-step entries, generous bathroom clearances, wide door openings, slip-resistant flooring, and placement close to the main house. Multigenerational living works when every family member keeps private space, which is why in-law suites built this way hold up over decades. Units built for family members today often serve later as guest quarters, a remote work studio, or a rental unit that helps generate rental income once the household changes shape again.
Why Concord Homeowners Choose Golden State ADUs as Their ADU Builder
Design, engineering, permitting, and construction sit with one accountable team that knows this city’s approval path. When a plan check comes back, nobody is pointing at anybody else.
- ADU specialists, not generalists. Accessory dwelling units are all we build. Our portfolio is ADUs, our designers draw ADUs, and our project managers run ADU schedules.
- Licensed and bonded. LIS. #1125656, with a 10-year structural integrity warranty and a 1-year fit-and-finish warranty on every project.
- Real references. 100+ happy customers and 18 Google reviews. Ask any ADU builder for project references before you sign.
- Local knowledge. Concord’s Building Division fees are valuation-based, with administrative, technology, planning, and waste-management charges layered on, and some outside-agency reviews require their own applications. We budget and schedule for that up front.
- Personalized service. One assigned on-site project manager, regular updates, and answers the week you ask for them.
When you compare bids, compare substance. A good ADU builder’s proposal spells out scope, site-work and utility allowances, foundation assumptions tied to your soil and slope, materials and finish allowances, written exclusions, a timeline, and a contingency. We do value engineering before plans are finalized, not after demolition starts. Many homeowners who see the real number early make better decisions about size, materials, and phasing, which is the entire point of fair and transparent pricing.
Our office is in Roseville, and we serve Concord and communities throughout California with scheduled site visits.
Get a Free Estimate for your Concord property.
How Your Concord ADU Project Works: Five Steps
- Free 1-hour walkthrough and site assessment. We review the parcel, setbacks, access width, utilities and electrical capacity, slope, trees, and flood screening, confirm the number and type of ADUs allowed on your property, then tell you honestly what the site supports.
- Design and value engineering. We compare a City pre-approved plan against a custom design, lock the layout, select materials and finishes, and align scope with budget before engineering starts. Design and permit plans typically take three to five months.
- Engineering, permit submittal, and agency coordination. Structural and civil engineering, submittal to the Concord Permit Center, and the separate fire, water, and school-district applications. Concord says complete ADU building permits are typically issued within 60 calendar days of a complete application.
- Construction. Once permits are approved, site preparation starts and construction begins. You get scheduled inspections, and Concord inspection requests generally go onto the next-business-day schedule, subject to availability. A new detached ADU typically takes three to four months, longer for larger or more complex work.
- Final inspection, closeout, and warranty. Sign-off, documentation, walkthrough, and post-project construction administration backed by both warranties.
These are typical ranges based on complete submittals and ordinary site conditions, not guarantees.
Building ADUs in Concord: Lots, Zoning Laws and Site Conditions
Most Concord surprises come from the age of the housing stock, not the accessory dwelling unit itself. Using 2019 to 2023 ACS data, 79.4% of Concord’s owner-occupied homes and 67.7% of its renter-occupied homes were built before 1980.
Older homes, older systems. Long before your project begins, we screen for undersized electrical panels, aging sewer laterals, narrow side-yard access, and prior unpermitted conversions. The City identifies North Todos Santos as Concord’s oldest and most historically significant neighborhood, and reports that much of Holbrook, Hillcrest, Uplands, and Sun Terrace was built during the 1940s through 1960s. Southeastern Concord along the Clayton Road corridor developed mainly in the 1960s and 1970s. Around Four Corners at Monument Boulevard and Oak Grove Road the property mix varies, so conversions often pencil better than new construction.
Zoning laws and size. Lot size sets your ceiling: 1,000 square feet on lots of 12,000 square feet or less, 1,200 on larger lots. The 18-foot height allowance near BART or Clayton Road buys vaulted extra living space without widening the building. Design matching to the main house applies to nonexempt ADUs, one more reason to keep the designer and the builder under one roof.
Terrain, soil, flood, and climate. Sloped or expansive-soil properties may require a geotechnical report and an alternate foundation. Parcels in mapped flood zones other than Zone X need additional documentation, and Special Flood Hazard Areas exist along the northern portion of the Walnut Creek channel. Concord summers are hot, so energy performance drives shade, window orientation, insulation materials, and heat-pump sizing. Wet-season grading needs erosion control, and exposed soil gets stabilized before rain.
Permit review in Concord. Plans go to the Building Division at the Permit Center, Building D, 1950 Parkside Drive. An ADU using City pre-approved plans carries a published review target of five business days for first review and five for subsequent review. A custom detached ADU follows the residential-new schedule of 20 business days first review and 10 for subsequent reviews. The free pre-approved plan program covers detached ADUs only, and the City’s ADU rebate page lists a September 30, 2026 deadline that has already passed, so confirm current programs rather than budgeting around one. Talk to one of our ADU specialists.
Frequently Asked Questions
Do I need a permit to build an ADU in Concord, CA?
Yes. It starts with a City of Concord building permit from the Building Division at the Permit Center, Building D, 1950 Parkside Drive, plus the separate outside-agency approvals the City does not route for you. Concord typically issues complete ADU building permits within 60 calendar days of a complete submittal, and we manage the full package on your behalf.
How much does it cost to build a 1,000 sq ft ADU in Concord?
Costs vary based on several factors, so we estimate during feasibility rather than publishing a fixed price. The variables are valuation-based City fees and their added charges, utility connections, any electrical service upgrade, foundation type, materials, and finish level. Concord also lists parkland fees of $5,508 or $8,345 for certain ADUs between 750 and 1,200 square feet, depending on size relative to the primary dwelling. Our online ADU Cost Estimator gives a starting range, not a quote.
What’s the most cost-effective way to build an ADU in Concord?
A detached unit on City pre-approved plans usually carries the lowest design and plan-review expense, thanks to the five-business-day review target. Those plans apply to detached ADUs only and are not always the better fit. Unusual lot shapes, slope, accessibility needs, privacy, or required architectural matching often make a custom design the smarter spend. We put both options side by side with real numbers before you choose.
How long does ADU construction take in Concord?
Typically three to five months for design and permit plans, then three to four months of construction. Custom detached ADUs follow Concord’s residential-new review schedule, while outside agencies can take longer and are best approached concurrently. These are typical ranges, not guarantees.
Can I rent out my Concord ADU, and will it add property value?
You can rent it long term, and that rental income can help offset mortgage payments, but Concord prohibits renting an ADU or JADU for fewer than 30 consecutive calendar days, so short-term listings are out. A permitted, well-built unit adds usable square footage, flexible space, and long-term property value. We do not publish income or return projections.
Do you serve my part of Concord?
Yes, from North Todos Santos and the Monument Corridor to the Clayton Road corridor and the hillside neighborhoods, along with communities throughout California. Our office is at 1001 Enterprise Way #100, Roseville, CA 95678, and site visits are scheduled in advance. If you are searching for an ADU builder near you in Concord, call (916) 909-2387 and we will book a walkthrough.
Start Your Concord ADU Project With a Free Initial Consultation
In one hour on your property, you get a feasibility read on your lot, a setback and access sketch, utility and electrical screening, a pre-approved versus custom comparison, and a realistic conversation about budget. Whether you want space for family members, a workspace, or a unit that can generate rental income, we will tell you straight whether the property supports it. Choosing an ADU builder is a six-figure decision, and that first meeting should give you clarity either way.
Complete applications move faster than incomplete ones, utility upgrades carry long lead times, and dry-season site work avoids rain delays.
Call (916) 909-2387, email office@gsadus.com, or visit us at 1001 Enterprise Way #100 in Roseville. Book A Consultation or Get a Quote.
