ADU Laws · 2026
Santa Clara County ADU Regulations (2026)
In Santa Clara County, you can build a detached ADU of up to 1,200 square feet on nearly any single-family lot, and your city must approve a complete application within 60 days with no public hearing and no neighbor sign-off. That is because California state law sets the floor and overrides any local rule that would be more restrictive. The local layer that still matters here is mostly process and zoning detail, not whether you can build, and in a county with some of the highest land values in the country, the economics of adding a unit are about as strong as they get.
The short version: State law guarantees you an ADU up to 1,200 sq ft with ministerial (no-hearing) approval in 60 days, 4-foot setbacks, and no owner-occupancy requirement. Santa Clara County cities (San Jose, Los Gatos, Sunnyvale, Cupertino and the rest) add their own permit process and a few zoning details on top, but they cannot take those state protections away. We confirm exactly how the rules apply to your address in a feasibility study.
State law is the baseline in every Santa Clara County city
Whether your property sits in San Jose, Los Gatos, Los Altos, Morgan Hill, Sunnyvale, Cupertino, Santa Clara, Mountain View, Milpitas, Campbell, or unincorporated county land, the same California ADU law applies as the minimum standard. Cities can add detail and run their own permit counter, but they cannot remove these protections.
| Rule | What state law guarantees |
|---|---|
| Maximum size | Up to 1,200 sq ft for a detached new-construction ADU |
| Guaranteed minimum | At least an 800 sq ft / 16 ft tall ADU, regardless of local rules |
| Setbacks | No more than 4 ft required on the side and rear |
| Approval type | Ministerial: no public hearing, no neighbor approval |
| Decision deadline | The city must approve or deny a complete application in 60 days |
| Owner-occupancy | Not required for an ADU (still required for a JADU) |
| Parking | At most 1 space, with broad exemptions (see below) |
| Impact fees | Waived for ADUs under 750 sq ft, proportional above |
This is why an ADU is one of the most predictable construction projects you can take on in Silicon Valley. On a standard lot it is a by-right addition, not a discretionary negotiation with the planning department. You can read the full state framework in our California ADU laws 2026 guide and our breakdown of whether you can build an ADU on your property.
Parking is rarely a real obstacle here
A Santa Clara County city can ask for at most one parking space per ADU, and the state exemptions are wide enough that the requirement usually falls away. You do not have to add parking if your property is within a half-mile walking distance of public transit, within one block of a car-share, in an on-street permit area, part of an existing or proposed structure, or when the ADU replaces a garage or covered parking. Between VTA light rail, Caltrain, and dense bus coverage across San Jose, Sunnyvale, Mountain View, and Santa Clara, a large share of lots in the county sit close enough to transit that no extra parking is needed. We cover the details in our guide to ADU parking requirements in California.
The local layer that actually matters in Santa Clara County
State law decides whether you can build and how fast. Each city decides the texture of the process: which forms, which department, and a handful of zoning details. None of these stop a well-planned ADU, but they shape how the plans are drawn and how smoothly the permit moves.
City permit process and timelines
San Jose, the county’s largest city, has invested heavily in streamlining ADUs and even offers pre-approved ADU plan sets to speed review. Smaller cities like Los Gatos, Los Altos, Saratoga, and Monte Sereno run their own counters with their own intake quirks, but all of them are bound by the same 60-day ministerial clock once your application is complete. The practical difference is mostly how quickly a city deems an application “complete,” which is exactly where having your plans and engineering done right the first time pays off.
Lot coverage, height, and design rules
Cities can apply objective design and development standards, like maximum lot coverage, height limits within the state-protected 16-foot floor, and where the unit sits relative to the main house. These vary from Cupertino to Morgan Hill, but because they have to be objective (not subjective taste), they are knowable in advance. We design the placement to fit your specific lot’s coverage and setback math before anything goes to the city.
Hillside and slope parcels
Parts of the county are hilly, including the foothills above Los Gatos, Saratoga, Los Altos Hills, and the Santa Cruz Mountains edge near Morgan Hill. A sloped lot can mean extra foundation engineering and grading, and the placement has to respect slope and geologic-hazard rules. This is one reason factory building works well here: the home is built about 97% in our Salinas factory while the site work and foundation are handled to match the terrain.
Fire access and defensible space
Some foothill and wildland-interface parcels sit in higher fire-hazard zones, which can affect driveway and access width, defensible-space clearance, and exterior materials. One thing that does not change: fire sprinklers are not required for the ADU unless they are already required for your main house under state law.
How this plays out city by city
The state baseline is identical everywhere, but the day-to-day feel differs by jurisdiction. Here is the practical picture in the places we build most across the county.
| Area | What tends to drive the local review |
|---|---|
| San Jose | Pre-approved plan options, streamlined intake, transit-based parking exemptions |
| Los Gatos / Saratoga | Foothill slope, design standards, smaller-staff counters |
| Sunnyvale / Santa Clara / Mountain View | Flat infill lots, strong transit, straightforward path on many parcels |
| Cupertino / Los Altos | Lot coverage and objective design standards, premium neighborhoods |
| Morgan Hill / Gilroy | More land per lot, room for larger models, occasional well/septic |
We deliver across this whole area from our Salinas factory. You can see local detail on our San Jose, Los Gatos, and Morgan Hill city pages.
Why the ADU math is so strong in Santa Clara County
This is where Santa Clara County stands apart. Land here is among the most valuable in the nation, which means an ADU does two powerful things at once: it adds a high-rent rental unit and it adds resale value backed by Silicon Valley land prices. The all-inclusive cost of the home is roughly the same whether you build it in San Jose or in a lower-cost county, but the income and appraisal upside in this market are typically much larger. That is the core reason ADUs pencil out so well here. For the numbers, see our guides on how much rent an ADU can earn and ADU appraisal and resale value.
What it costs and how long it takes
A Framework First ADU runs $180,000 to $557,000 all-inclusive, and the words “all-inclusive” are the part that matters. That single number folds in a permitting budget, plans, the foundation, the factory build, delivery and crane set, utility hookups, appliances, and the final inspection, and because permit costs are set city by city, we confirm the real figure for your address in the feasibility study rather than guessing at one here.
We build 14 models from 405 to 1,200 sq ft in three styles: Classic Craftsman (our standard), Urban Farmhouse, and Ultra Modern. A few popular points on the lineup:
| Model | Size | Layout | All-inclusive price* |
|---|---|---|---|
| Four Fifty | 450 sq ft | Studio, 1 bath | $180,000 |
| Six Sixty | 660 sq ft | 1 bed, 1 bath | $287,000 |
| Nine Forty-Five 3/2 | 945 sq ft | 3 bed, 2 bath | $434,000 |
| Twelve Hundred U | 1,200 sq ft | 3 bed, 2 bath | $557,000 |
*Includes a permitting budget, not a final permit total. Permit costs and property-specific site work like septic or retaining walls vary by parcel and are confirmed in your feasibility study.
Most projects deliver in 4 to 9 months, because the home is being built in the factory while permits and the foundation move in parallel. See the full lineup on our models page and run your own numbers with the ADU cost calculator.
Frequently asked questions
Do I need owner-occupancy to build an ADU in Santa Clara County?
No. State law has permanently suspended the owner-occupancy requirement for standard ADUs, so you can build one and rent out both the ADU and the main house. The exception is a JADU (a junior ADU up to 500 sq ft created inside the walls of an existing home), which still requires the owner to live on the property. For the difference, see our JADU vs ADU guide.
How fast can I get approved in San Jose or another Santa Clara city?
Once your application is complete, state law requires the city to approve or deny it within 60 days, with no public hearing. The real variable is how quickly a city deems your application complete, which comes down to having complete, correct plans and engineering. San Jose’s pre-approved plan options can shorten that further. Our team handles the submittal and the back-and-forth so the clock starts as early as possible.
Can I build an ADU plus a JADU on the same lot?
Yes. State law allows a single-family lot to have the primary home plus one detached ADU plus one JADU. That means up to three households on a lot that today holds one, which is a meaningful play in a land-constrained market like Santa Clara County. We map out which combination fits your parcel in the feasibility study.
How big an ADU can I actually build?
Up to 1,200 sq ft for a detached new-construction ADU, and the city must allow at least 800 sq ft and 16 feet of height regardless of local rules. The right size for you depends on your lot, setbacks, coverage limits, and goals. Our guide on how big an ADU can be in California walks through the limits in detail.
Who handles the permits, the city, and the inspections?
Our team does. Permitting, plan check, city coordination, delivery, and the final inspection are all part of our process. Your all-inclusive price carries a permitting budget, and the exact cost for your address gets confirmed during the feasibility study. You are not standing in line at the planning counter or chasing an inspector. You can see the full sequence on our process page.
Every lot in Santa Clara County is a little different, and the only way to know exactly which city rules, coverage limits, or slope considerations touch your address is to look at the parcel itself. Start your feasibility study and our team will tell you what is possible on your property, what the permit path looks like, and what your all-inclusive number would be.