ADU questions, answered straight.
32 of the questions we actually get asked, answered without the hedging. The rules here are California state baselines drawn from the Department of Housing and Community Development's ADU Handbook — including the changes that took effect in January 2026, which most of what you'll read online predates.
Your city layers its own ordinance on top of all of this, and two neighbouring cities routinely reach different answers. For your address specifically, ask Keyli — she looks up the city's own site — or book the free site walk.
Can I build an ADU?
Can I build an ADU on my lot?
Most likely yes. Under current state law most single-family lots in California can add at least one ADU, and many can add a detached ADU plus a JADU carved out of the existing house. Multifamily lots have their own, more generous allowances.
What the ordinance permits and what your lot can actually take are two different questions, though. Setbacks, existing structures, easements, where the sewer lateral and the panel are, and how a crew would physically get equipment into the back yard all narrow it. That is exactly what the free site walk settles, and it is the only honest way to answer for a specific address.
How big can my ADU be?
Bigger than most people expect, and the number depends on which rule is doing the work.
If your city has a compliant ADU ordinance, its maximum has to allow at least 850 square feet of interior livable space, or 1,000 square feet if the unit has more than one bedroom. Where a city has no compliant ordinance, state law allows up to 1,200 square feet for a new detached ADU. And separately, a city cannot use lot coverage, floor area ratio, open space, or front setback rules to block an ADU of at least 800 square feet that keeps four-foot rear and side setbacks.
Cities are free to be more generous than any of that, and some are. Converting existing space — a garage, or part of the house — is not subject to unit size limits at all.
How many ADUs can I put on my property?
On a single-family lot, generally one ADU plus one JADU. The JADU has to be carved from the existing house rather than built new, so the common arrangement is a detached unit in the back yard and a JADU converted from a bedroom, an attached garage, or a similar existing space.
Lots with an existing multifamily building are treated differently and can support considerably more — up to eight detached ADUs, capped at the number of units already on the lot.
What is the difference between an ADU and a JADU?
Size, and where it comes from.
An ADU is a full independent unit with its own kitchen, bathroom, and entrance. It can be detached, attached to the house, or converted from an existing structure like a garage. Up to 850–1,200 square feet depending on the rule that applies.
A JADU is up to 500 square feet and must be created inside the walls of the existing single-family home. It may share sanitation facilities with the house or have its own — and since January 2026 that choice determines whether an owner has to live on the property. A JADU is usually the cheaper and simpler permit, but it takes space from the house rather than adding it.
Plenty of properties do both.
Is a garage conversion faster than building new?
Usually, yes — the structure, the foundation, and often the utilities are already there, so a conversion skips the most expensive and slowest parts of a ground-up build.
State law helps more than people expect. You cannot be required to replace the parking spaces you lose. No setback is required for a unit created inside an existing structure. Unit size limits, open space, and landscaping requirements do not apply to a conversion of existing space. And if a detached garage is being demolished and replaced with an ADU, the city has to handle the demolition permit at the same time as the build permit rather than making it a separate queue.
The trade is that you give up the garage, and an older slab or framing sometimes needs work the drawings did not anticipate. We look at both on the site walk.
Should I look at a prefab ADU?
It can be a good fit when the timeline matters more than the details. A factory-built unit arrives finished and gets set on a permitted foundation, so the on-site phase is shorter and less weather-dependent.
What it does not skip is the site work: foundation, utility connections, access, and the permit itself all still happen, and a tight or sloped lot can make delivery and craning the harder problem. Bayfront installs prefab units as well as building custom, so we have no reason to push you either way — we will tell you which one your lot actually favours.
Do I need a large lot?
There is no minimum. Cities are specifically prohibited from imposing a minimum lot size requirement for an ADU, and they cannot use lot coverage or open space rules to block an 800-square-foot unit that keeps four-foot side and rear setbacks.
Small and awkward lots are a large share of what we build on. Sam specialises in hard-to-build spaces, and several of our floor plans exist because a standard rectangle did not fit.
What if my property is in an HOA?
An HOA cannot flatly prohibit an ADU on a single-family lot — state law limits them to reasonable restrictions that do not unreasonably increase the cost or effectively prohibit the unit. In practice that leaves them room on things like exterior materials and colours, not on whether you may build at all.
Worth reading your CC&Rs early so any architectural review runs alongside the city process instead of after it. Bring them to the site walk.
Permits, rules, and timeline
How long does it take to get an ADU permit?
State law puts two clocks on the city, and both were tightened in January 2026.
The city has 15 business days to tell you in writing whether your application is complete — and if it is not, to list exactly what is missing and how to fix it. Once the application is complete, it has 60 days to approve or deny it where there is already a house on the lot. The statute now says "approve or deny" rather than the older, weaker "act on," and a denial has to come back in writing with a full list of what is deficient and how to remedy it.
The statutory clock is not the whole calendar, though. Real timelines turn on how quickly plan-check corrections get cleared, which is the part we manage rather than hand back to you.
Can the city just say no?
Not on taste. ADUs and JADUs must be permitted ministerially — reviewed against an objective checklist, with no discretionary review and no hearing. There is no design review board deciding whether they like the look of it, and ministerial approvals are exempt from CEQA.
Because the review has to be objective, the standards themselves have to be objective: numbers like heights and setbacks, or specified colours and materials. Subjective language — "privacy," "compatibility with the neighbourhood," "design harmony," "must match the existing architectural style," "high quality materials" — requires judgement and cannot be imposed on an ADU.
A city can still deny an application that genuinely fails an objective standard. It has to tell you which one, in writing.
Do I have to add parking?
Often not. Parking for an ADU can never exceed one space per unit or per bedroom, whichever is fewer, and it can be tandem in the driveway. Guest parking can never be required.
No parking at all may be required where the ADU is within a half-mile walk of public transit, inside a historic district, part of the existing house or an accessory structure, in an area where on-street permits are required but not offered to the ADU's occupant, within a block of a car-share vehicle, or submitted together with a new primary dwelling.
And you never have to replace parking you lose: when a garage, carport, covered structure, or uncovered space is demolished or converted to build an ADU, the city cannot require those spaces to be replaced.
Will I have to pay impact fees?
Impact fees are prohibited entirely on an ADU of 750 square feet or less of interior livable space, and on a JADU of 500 square feet or less. Above 750 square feet, an impact fee on an ADU has to be charged proportionally to the size of the main house rather than as a flat charge.
What any particular city's fees come to is a question for that city, and what your project costs is a question we answer after walking the lot. We do not quote from a fee schedule.
How close to the property line can it go?
Four feet. A city may impose objective setbacks, but it cannot require more than four feet from the side and rear lot lines for an attached or detached ADU.
Front setbacks work differently — a city can apply them, but not so as to preclude an ADU of at least 800 square feet. If an 800-square-foot unit will not fit in the back yard, the city has to allow it in the front setback if that is what it takes.
No setback at all is required for a unit created inside an existing structure, or for a new structure built in the same footprint and dimensions as the one it replaces. Coastal Zone properties can carry additional setbacks under a local Coastal Program.
My unit was built without permits. Can it be legalised?
Usually, and the path is better than most people expect. A city cannot deny a permit for an unpermitted ADU built before January 1, 2020 on the grounds that it violates building standards or does not comply with state ADU law or the local ordinance.
Cities are required to publish how this works, including a checklist of the conditions that would make a building substandard. The genuinely useful part: before you apply, you may get a confidential third-party code inspection from a licensed contractor to find out what condition the unit is actually in and what the work would involve — without that becoming a code enforcement matter.
That assessment is the kind of thing we do on a site walk. Milpitas also runs its own "Safe ADU" legalisation program.
Do I have to deal with the city myself?
No. Permit management is one of the three things we do in house — plan check, corrections, and sign-offs end to end. The owner does not deal with the city.
That matters more than it sounds. The statutory clocks govern the city's response time, not how fast corrections come back, and a correction cycle that sits on someone's desk for three weeks is the single most common reason an ADU takes longer than it should.
Which rules apply in my specific city?
Every city layers its own ordinance on top of the state baseline — design standards, height limits, parking near transit, historic overlays, fire-severity requirements, utility connection rules. Two neighbouring cities routinely reach different answers on the same question, which is why we will not quote you a number for a named city from memory.
Bayfront publishes an official-links directory at /resources with the ADU page for every city we build in, plus the county authorities, so you can read the current rule from the source. Keyli will look up a specific city against that city's own site rather than guessing. The best county-wide starting point is Santa Clara ADU (aduscc.org), run jointly by the county and its cities.
Renting, family, and property value
Do I have to live on the property?
For an ADU, no. A city cannot impose an owner-occupancy requirement on an ADU. The old sunset date on that prohibition was removed, so it is the standing rule rather than a temporary one. The single exception is an ADU that has been sold separately to a qualified buyer.
For a JADU, it depends — and this changed on January 1, 2026. Owner occupancy is required only if the JADU has shared sanitation facilities with the main house. If the JADU has its own separate sanitation facilities, owner occupancy is not required. Where it does apply, the owner can live in either the JADU or the remaining part of the house.
Almost everything written before 2026 says a JADU always requires an owner on site. That is out of date, and it is worth knowing if you ruled a JADU out on that basis.
Can I rent it out on Airbnb?
Generally no, and for a JADU definitely not.
Cities are allowed to require that an ADU or JADU be rented for terms longer than 30 days, and most do — which takes short-term vacation rental off the table. For JADUs this is no longer optional: since January 2026 a JADU cannot be used as a short-term rental at all, and if rented must be rented for more than 30 days.
Long-term rental is the intended use, and it is what makes the numbers work anyway.
Can I sell the ADU separately from my house?
Only if your city has opted in. By default an ADU cannot be sold separately. A city may adopt an ordinance allowing the primary dwelling and the ADU to be sold separately as condominiums, but that requires the city to act — it is not automatic.
San José is the notable local example. Worth asking about specifically if separate sale is part of your plan, because it changes the financing and title picture substantially, not just the paperwork.
Will building an ADU reset my property taxes?
Not on the whole property. Under Proposition 13, adding an ADU triggers a reassessment of the new construction only — the assessor adds the value of what you built to your existing assessed value. The original house keeps its existing base year value and is not reassessed.
The county assessor is the authority on your specific bill, and it is worth a call to them before you plan around a number. Brad can walk you through how the arithmetic usually shapes up against the rental side.
Does an ADU actually add value?
It adds permitted, on-record square footage that follows the property, which is a different thing from a renovation that only changes how the house feels. Beyond resale, the common reasons our clients build are rental income against a mortgage, room for aging parents or adult kids who need to be close but not in the house, and a dedicated office or studio.
Brad is a licensed Real Estate Broker with ten years helping investors, so the conversation about what the unit adds in income and long-term value is one we have properly rather than hand-wave.
Can you help me find a tenant?
Yes. Bayfront is licensed with the California DRE, so once the unit is finished we can also place a renter in it. If rental income is the point of the project, that means you are not handing a finished ADU off to a separate agent and starting a new relationship from scratch.
Working with Bayfront
What happens on the free site walk?
We come to the property and give you a straight answer about what it can support. That means walking the lot with setbacks in mind, finding the sewer lateral and the electrical panel, looking at access for equipment, and identifying the things that decide feasibility but never appear in a rulebook — easements, grade, existing structures, a neighbour's tree.
You get an honest read on whether the project makes sense, roughly what path it would take, and what it would involve. No obligation and no pressure. If the answer is that your lot is a poor candidate, we would rather tell you at that visit than after you have paid for drawings.
Who does the design and engineering?
We do, in house. Architectural design and structural engineering both sit inside the company and are coordinated together, which is the main reason things do not get lost between trades or turn into a change order halfway through framing.
Six example floor plans are published at /floor-plans. They are starting points rather than a fixed catalogue — setbacks, lot coverage, and your city's rules decide the final footprint, and we adapt the plan to fit rather than forcing the lot to fit the plan.
How much does an ADU cost?
The honest answer is that we do not quote a price without seeing the property, and we will not give you a cost-per-square-foot number over chat. Two lots on the same street can differ by a lot once utility runs, grade, access, and the condition of what is already there come into it, and a number pulled from a blog is not a quote.
What we will do is give you a real number after the free site walk, with the scope written down. Bayfront's model is fixed scope and fixed schedule, with no change-order surprises — which only works if the number is built on an actual look at the property.
If you want to work the numbers yourself in the meantime, the feasibility calculator gives you a cost range, the monthly payment, and whether the rent covers it, with every assumption adjustable.
How long does the build actually take?
A detached ADU is our longest build, at about six weeks of construction. Garage conversions, JADUs, and prefab installations all come in shorter — the structure, the foundation, or both already exist.
Two things sit outside that six weeks and it is worth being clear about them, because most timelines you will read quietly fold them in. Permitting comes first and runs on the city's clock: state law gives it 15 business days to tell you whether your application is complete and 60 days to approve or deny it once it is. Inspection scheduling is the other, and it depends on how booked the city's inspectors are that month.
We give you a real schedule once we have walked the lot and know which permit path you are on, rather than a number that sounds good in a chat window.
Can I stay in my house while you build?
Almost always, yes, and we plan the work around it. A detached unit goes up in the back yard and barely touches the house.
A carve-out is the one that gets closer to you — a JADU or an interior conversion means that part of the house is a work area for a while, and there is usually some shifting around inside. Even so, we very rarely need anyone to move out.
Is there a warranty?
Twelve months from the certificate of occupancy.
Do you only build ADUs?
Yes, deliberately. ADUs are all we do — no kitchen remodels, no additions, no general contracting. That is why the permit path, the plan-check corrections, and the city relationships are familiar rather than a first attempt.
CSLB license #1131251, licensed and insured, and 100% of our projects are permitted and inspected.
Who am I actually working with?
Sam Saidian and Brad Pickens, the two founders, with about 30 years of combined experience between them. Sam is the boots-on-the-ground founder and handles everything from site feasibility through the final walkthrough; he comes from a family of real estate developers and specialises in hard-to-build spaces. Brad is a lifelong Silicon Valley resident from a family of general contractors and real-estate investors, a licensed Real Estate Broker, and handles the numbers side — rental income and long-term property value.
You get one dedicated crew and a single point of contact through final inspection and keys in hand, not a rotating cast.
What areas do you serve?
The Greater Silicon Valley corridor, from Palo Alto south to Hollister.
That covers Santa Clara County — Palo Alto, East Palo Alto, Los Altos, Los Altos Hills, Mountain View, Sunnyvale, Cupertino, Santa Clara, Milpitas, San Jose, Campbell, Saratoga, Monte Sereno, Los Gatos, Morgan Hill, and Gilroy — plus San Benito County, including San Juan Bautista and Hollister.
Unincorporated parcels are permitted through the county rather than a city, which is a different process and a different set of standards.
How do I get started?
The free site walk is the whole first step. Use the "Explore Feasibility" button anywhere on the site to book one, or the call and text button if you would rather just talk to someone.
If you would rather get your bearings first, Keyli can answer questions about the rules, the permit path, and what building on a Bay Area lot involves — she will look up your city against that city's own site rather than guessing, and she will tell you when a question genuinely needs Sam or Brad.
Still have a question?
Keyli knows the rules for every city we build in and will search that city's own site rather than guess. For what your lot can actually take, that's what the free site walk is for.