ADUs
ADU construction and ADU builders across the Bay Area
A second home on the lot you already own. California law is now firmly on your side, and a well built ADU houses family, earns rent, or does both.
The short version
ADU construction across the Bay Area, from lot check to lockup.
California has spent the last several years stripping away the local rules that used to block accessory dwelling units. Cities must now approve a compliant ADU application within 60 days, and most owner occupancy requirements are gone.
That does not make it simple. Utility connections, fire sprinklers, setbacks, and how the ADU meters separately from the main house are where these projects get expensive if nobody planned for them. We plan for them first.
Typical timeline · ADU timelines get quoted online as though every lot is the same. They are not. Utility connections, setbacks, fire access and your city's queue all change the date. State law does force cities to act within sixty days on a compliant application, which helps, and once we are approved our crews build fast because we are not subcontracting the shell out. Call us and we will give you the real picture for your lot.
Scope
What an ADU project includes
Site work, structure, utilities and city hall, all inside one fixed agreement.
- Feasibility and siting What your lot allows, where it can sit, and what it will really cost to connect.
- Plans and engineering Full architectural set, structural calculations and Title 24 energy compliance.
- Permit management Submittal, plan check corrections and every inspection through final.
- Site work and foundation Grading, drainage and a new foundation engineered for your soil.
- Full structure Framing, roofing, siding, windows, doors, insulation and drywall.
- Utilities Water, sewer, gas and electrical runs, with separate metering when you want it.
- Kitchen and bathroom A real kitchen and a real bathroom, built to the same standard as the main house.
- Finish and handover Flooring, paint, fixtures, appliances and the final certificate of occupancy.
Honest numbers
ADU construction costs in the Bay Area.
Most contractors will not put a number on a web page. Here is ours, so you can find out whether we are in your range before you spend an afternoon on a consultation.
$190,000 to $500,000
Garage conversions are the cheapest route to an ADU. New detached construction costs the most because it needs its own foundation, roof and utility connections.
Garage conversion ADU
Existing structure converted, insulated, and fitted with kitchen and bath.
Attached ADU
Built onto the main house, sharing one wall and some utility runs.
Detached ADU
New standalone structure with its own foundation, roof and connections.
These are typical ranges for completed Bay Area projects, not quotes. Costs move with the city and the age of the house, so your fixed price comes after we walk the space.
How it works
Five steps, start to finish.
The walkthrough
We come to you, look at the space, and talk about what you actually want. It is free, it takes about an hour, and there is no sales pitch at the end of it.
The contract and your price
An itemized breakdown of what every part of your project costs, a schedule for how long the work will take, and a clear payment structure, all in writing before anything begins. Read it closely and ask us anything. A contract you fully understand on day one is why the project ends with no surprises on the final bill.
Design and drawings
Measured plans, elevations and a professional 3D rendering of your space, so you can review the finished design before a single wall is touched. You approve it, and only then does the build begin.
Permits and build
We pull the permits, meet the inspectors and build it. You get a weekly update and a site we sweep every evening.
Walkthrough and warranty
We walk the finished job with you, clear the punch list, and hand over the warranty. And if you ever need us afterward, we will be right here, as we have been since 1989.
What clients say
300+ five star reviews from Bay Area homeowners.
The team turned our kitchen into a beautiful, functional space. They designed a layout that maximizes every inch and paid close attention to every detail.
As an architect, I highly value attention to detail, precision and timeliness, and Daniel and his team excelled in all of these areas.
Clarity Construction provided an exceptional experience. Daniel and his team were professional, knowledgeable and communicative throughout.
The team was outstanding. Friendly, communicative, and they kept me updated every step of the way. The final result is absolutely beautiful.
Straight answers
California ADU law is on your side.
The rules that make ADUs work now.
State law has made the ADU the most protected project in California housing. Approval is ministerial, no hearings and no discretionary review, and the city must decide a complete application within sixty days. Side and rear setbacks are capped at four feet. Every lot must be allowed at least eight hundred fifty square feet, a thousand for two or more bedrooms. And units under seven hundred fifty square feet are exempt from local impact fees, which used to add five figures. We design to these rules from day one, and we know them better than most counters do.
Pre-approved plans, if speed is the goal.
San Jose, Santa Clara, Sunnyvale, Mountain View and Cupertino all run pre-approved ADU plan programs: designs the city has already checked, so review covers only your site and utilities. San Jose says a complete package can be permitted the same day as its review meeting; Mountain View cites up to thirty days saved. If a pre-approved set fits your lot and your taste, it is the fastest legal square footage in the state, and we build from those sets at the same fixed-price standard as our custom work.
Already have an unpermitted unit?
California's amnesty law means a city cannot deny legalization of an ADU built before 2020 just because it was unpermitted, unless it is genuinely substandard on health and safety. If a past owner left you a converted garage of uncertain provenance, we can survey it, tell you what legalization takes, and carry it through. A legal unit rents openly, appraises, and stops being a liability sale-day surprise.
ADU Construction questions
What people ask us about ADU construction.
How much does an ADU cost to build in the Bay Area?
A detached ADU generally runs $350,000 to $500,000 across the Bay Area, which works out around $500 to $650 per square foot. Converting an existing garage is far cheaper at $190,000 to $250,000 because the structure and foundation already exist.
Am I allowed to build an ADU on my lot?
In almost all cases, yes. State law requires California cities to allow at least one ADU on a single family lot, and to approve a complete and compliant application within 60 days. The real questions are size, placement and utility connections, which we check against your specific parcel first.
Do I have to live on the property?
State law removed owner occupancy requirements for ADUs permitted through the current statutory framework. Rules do continue to change, so we confirm the requirements that apply to your parcel and your permit date before you commit.
Can I rent the ADU out?
Yes. Long term rental is allowed. Short term rental of under 30 days is where cities still restrict, and cities like San Jose have their own rules on that, so tell us your intention early and we will confirm what applies.
Does an ADU need a separate electric meter and address?
It does not have to, but separate metering makes renting much simpler and is worth the cost if you plan to rent. It needs its own address for utilities and mail either way. We handle the address assignment and the utility coordination.
Also worth a look
Related services.
Whole Home Renovation
Every room at once, under one contract and one schedule that holds.
$200k to $600kHome Additions
More square footage, tied in so cleanly it looks like it was always there.
$400 to $650 / sq ftGarage Conversion
The cheapest square footage you own. Foundation and roof are already there.
$100k to $250kFree consultation
Let us price your ADU construction properly.
Tell us what you are planning. We will walk the space, talk through what it really takes, and put a fixed price in writing.