Golden State ADUs is a design-build company specializing in Accessory Dwelling Units (ADUs) for Morgan Hill homeowners and families throughout California. We design, permit, and build under one accountable team: in-house architectural design, structural and civil engineering, permitting, and construction services. We are licensed and bonded (LIS. #1125656), trusted by 100+ happy customers, and every ADU project we complete carries a 10-year structural integrity warranty and a 1-year fit-and-finish warranty.
An accessory dwelling unit is allowed on single-family and multi-family residential parcels in Morgan Hill, and the city asks owners to confirm parcel zoning and any additional requirements with the Planning Division before applying for a building permit. Knowing local zoning, California ADU law, and permit rules before drawings start is the job of your ADU contractor, not yours. So is carrying liability insurance and workers’ compensation you can verify before you hire any ADU builder.
Start with a free 1-hour walkthrough and find out what your lot can actually hold before you buy plans. See our full ADU design, permitting, and construction services.
Our ADU Construction Services in Morgan Hill, California
We handle design, engineering, permitting, and construction in-house, so you are never coordinating a separate architect, a separate engineer, and a separate builder who each blame the other. We are not a general contractor who subcontracts the drawings out: our architects, engineers, licensed contractors, and project managers work for the same company, which is what streamlining a build really means. That matters about 20 miles south of San Jose, where land is valuable and a second unit changes what a property can do for a family. Homeowners comparing ADU builders here often end up with design on one contract and construction on another. With us it is one project team and one point of accountability, from garage conversions to ground-up detached units.
Detached ADUs, Custom ADUs and Tiny Homes
Detached ADUs are standalone structures built elsewhere on your property, from compact studios and tiny homes up to 3-bedroom units, ADUs with garage space, and Retirement ADUs for multigenerational living. We build custom ADUs more often than repeat layouts, because almost no two Morgan Hill lots are shaped alike. Custom ADUs get drawn around how your family actually lives, whether that means a ground-floor bedroom for a parent or a quiet workspace away from the main house. Morgan Hill’s 2026 permit records show the local spread: a new 498-square-foot detached ADU on La Vela Court at a $150,000 valuation, and a 1,000-square-foot detached unit with a three-car garage on Morgan Avenue at $387,790. Those are declared permit valuations, not quotes. Our designs lean efficient and eco-friendly, with layouts that keep usable yard space instead of swallowing it.
Attached ADUs and Garage Conversions
Attached ADUs are built within or onto your existing house, and garage conversions turn an underused garage into finished living space. Garage conversions are often the quickest legal second unit on an older house. Morgan Hill issued garage conversions in 2026 valued at $49,000 and $70,000, plus a $154,880 conversion of an existing 791-square-foot structure on Claremont Drive. Conversions usually move faster than new construction, because the shell already exists and the work is part remodeling, part new build. That remodeling scope commonly includes slab repair, raised floors, insulation, egress windows, and a rebuilt wall where the garage door was. Older structures still need their legal status, framing, and utilities verified before any ADU builder promises you a budget.
Design, Engineering and Permitting Services, Done for You
Permits, paperwork, compliance: done for you. Our in-house design and engineering company, Golden State Design & Engineering, prepares construction drawings that include site plans, floor plans, and utility details built to the city’s ADU checklist and current California Building Standards Codes, then submits electronically in PDF format to permits@morganhill.ca.gov. The same professionals answer plan corrections, so nothing sits waiting on an outside office. If you are considering Morgan Hill’s pre-approved ADU plans, know that they still require property-specific site planning, emergency-access review, foundation design, and permitting services. Interior design bundles are available as an add-on.
Why Morgan Hill Homeowners Choose Us as Their ADU Contractor
Choosing an ADU contractor is most of the outcome, and homeowners here compare builders carefully. You get one accountable design-build team from the first walkthrough to the city’s final sign-off, with transparent pricing that separates design, engineering, city plan review, permit, school, impact, and utility costs so nothing lands as a surprise in month five. ADUs are all we do, and we are not a custom homes builder taking ADU work on the side.
- Proven work and reviewable proof: 100+ happy customers, 18 Google reviews, and a portfolio our clients are welcome to go through before committing.
- Licensed, bonded, insured: LIS. #1125656, with liability insurance and workers’ compensation coverage we document on request. Ask the same of every contractor you interview.
- Warranties in writing: a 10-year structural integrity warranty and a 1-year fit-and-finish warranty, backed by more than a decade of collected experience building residential projects.
- Value engineering before drawings are final: Morgan Hill applies proportional impact fees to units of 750 square feet or more and routes projects over 499 square feet of residential space to Morgan Hill Unified School District for school fees. Those thresholds belong in the size conversation on day one, when they are still worth real dollars to your family’s budget.
Nationally, ADU budgets run from around $30,000 for a modest garage conversion to well over $300,000 for a large detached build. Many builders price by the square foot, and we do not, because site conditions, utilities, and finishes decide it. We do provide a firm contract price once the architectural design is complete and the project scope is known.
On distance: our Sacramento-area office sits roughly 154 road miles from Morgan Hill, about 2 hours 43 minutes down I-680 and US-101. We answer that with planned site visits, a dedicated project manager, and regular updates by call and email, so you get peace of mind instead of chasing us. Let’s connect and discuss your property.
Our ADU Building Process, Step by Step
- Free 1-hour walkthrough and feasibility review. We look at zoning, setbacks, lot coverage, overlay zones, utility routes, electrical service capacity, and emergency access. If your lot will not support what you want, we tell you then.
- Design and engineering. Collaborative and iterative, with budget and value engineering settled before drawings are finalized. Bring your ideas and we turn them into a buildable plan, with floor plan, foundation, and service loads designed together rather than in sequence by three firms.
- Permitting. PDF submittal to Development Services, correction responses, and fee coordination. Morgan Hill’s ADU ordinance provides a 60-day approve-or-deny review period for qualifying applications on lots that already have a dwelling.
- Construction and completion. A project manager runs the site through concrete work, framing, utility installation, and finishes, with progressive inspections and skilled trades held to our standard of detail. At final inspection, Morgan Hill signs a Residential Dwelling Occupancy Approval on the inspection card rather than issuing a conventional Certificate of Occupancy.
Typical ranges: 3 to 5 months for design and permitting, 3 to 4 months of construction. Those are typical, not guaranteed, and a clean application is the biggest factor.
Building an ADU in Morgan Hill: Permits, Terrain and California Law
Morgan Hill ADU permits are processed through the City of Morgan Hill Development Services Department, with Building & Fire Prevention and Planning at 17575 Peak Avenue. Plan-review and building-permit fees are calculated from total construction valuation, which is why your design decisions and your fee bill are the same conversation. The city also offers a preliminary engineering fee estimate for $573 under the fee schedule effective July 1, 2026.
Four local conditions catch homeowners off guard, and we screen for all of them during feasibility:
- All-electric detached units. Morgan Hill generally prohibits new natural-gas infrastructure in detached ADUs unless electrical inadequacy is demonstrated through load calculations. We run those early so any panel upgrade is priced, not discovered.
- Street and sidewalk improvements. The city’s ADU checklist includes a review trigger tied to project valuation and the ADU’s size relative to the main house.
- Street cuts. If your street is on Morgan Hill’s five-year moratorium list, a utility cut may be restricted, which changes how we route service.
- Geologic hazard areas. The city may require a geologic report, a real consideration on the East Dunne foothill slopes.
Morgan Hill sits in a valley roughly four miles wide between the Santa Cruz Mountains and the Diablo Range, so your location on a hillside parcel or on the valley floor is not the same engineering problem. The city’s Emergency Operations Plan notes that hillside soils can become saturated during winter rains and that mountain watersheds create continuing creek flood potential. We sequence excavation, foundations, and trenching around that, with erosion controls planned rather than improvised.
Our engineers design to Morgan Hill’s adopted criteria: Climate Zone 4, Exposure C, Seismic Design Category D, and 92 mph Risk Category II wind speed. California energy and accessory dwelling unit standards shift regularly, so we design to the code edition in force at submittal. On site, we work within city construction hours of 7 a.m. to 8 p.m. Monday through Friday and 9 a.m. to 6 p.m. Saturday, with no work on Sundays or federal holidays.
The housing stock shapes the work too. Morgan Hill was 59.0% single-family detached in 2020, and the postwar houses with detached outbuildings near Claremont Street, site of the city’s first tract housing in 1959, are prime conversion candidates. Larger east-side parcels allow the bigger detached programs the permit record shows, the kind a family builds when relatives are moving in from San Jose or elsewhere in the Bay Area.
Frequently Asked Questions
How much does it cost to build an ADU in Morgan Hill?
Expect a range from roughly $30,000 for a simple conversion to over $300,000 for a large detached ADU with a garage. Garage conversions sit at the lower end of that span. Permit valuations are not all-in budgets, which also include design, engineering, city fees, utilities, and finishes. Many homeowners handle financing with a home equity loan, and most banks offer ADU construction lending.
How long does Morgan Hill take to approve ADU plans?
Morgan Hill’s ADU ordinance provides a 60-day approve-or-deny review period for qualifying applications on lots with an existing dwelling. That clock assumes a complete, accurate submittal; correction cycles add time. Our typical range is 3 to 5 months for design and permitting, then 3 to 4 months of construction.
Do I pay impact fees if my ADU is under 750 square feet?
Morgan Hill’s ADU checklist applies proportional impact fees to units of 750 square feet or more, so smaller units fall below that trigger. California law also allows development impact fees to be waived for ADUs of 749 square feet or less, though local rules vary. We put every threshold on the table during design.
Can I have gas appliances in a detached ADU in Morgan Hill?
Generally no. Morgan Hill prohibits new natural-gas infrastructure in detached ADUs unless electrical inadequacy is demonstrated through load calculations. We run service and load calculations during design so your panel capacity, heat pump, and appliance package are settled before permitting.
Does an Accessory Dwelling Unit Add Property Value, and What Is the Drawback?
The honest drawback is the upfront commitment: cost, city fees, and several months of activity in your yard. The benefits sit on the other side. A well-built accessory dwelling unit on a lot with an existing primary residence can add property value, create rental income in a tight San Jose and South Bay market, host guests and friends, or give a parent independent living space a few steps from your door.
Do You Serve My Part of Morgan Hill, San Jose and the Rest of California?
Yes. We design, permit, and build in downtown and the Monterey Road area, the East Dunne foothills, Madrone, and the Claremont-area tract neighborhoods, in nearby San Jose and the wider Bay Area, and throughout California.
Start Your Morgan Hill ADU with One Team
Get feasibility answers before you spend money on plans. Morgan Hill asks owners to confirm parcel zoning with the Planning Division first, and that review is part of your free 1-hour walkthrough. Whether you are weighing garage conversions or a detached build, schedule a meeting, book a free 30-minute consultation, or run numbers through our ADU cost estimator and see your vision come to life without the worry.
Contact us at (916) 909-2387, email office@gsadus.com, or find us at 1001 Enterprise Way #100 in Roseville. Book a consultation with one of our ADU specialists.
