ADU Laws · 2026
Santa Clara County ADU Fees (2026): What Applies to You
The fact that changes Santa Clara County ADU fees the most is a state rule, not a county one. Under Government Code section 66311.5, no city, county, special district or water corporation can charge an impact fee on an ADU with 750 square feet of interior livable space or less. Above that, impact fees must be proportional to your main home. School fees follow their own line, and the rest depends on who issues your permit, which in Santa Clara County is usually your city, not the County.
The short version: At 750 sq ft or less, an ADU pays no city, county or special district impact fees, like park and traffic fees. Larger units can be charged fees scaled to the main house. School fees are the one to watch: exempt under 500 sq ft, your district’s call above that. Building permit and plan check fees sit outside the waiver: cities set their own, and on unincorporated land the County charges a percentage of your construction valuation. We confirm your parcel’s fees in the feasibility study, before you sign.
On this page
The state fee rules that apply everywhere in Santa Clara County
These state rules apply in every city and on unincorporated land. They come from Government Code 66311.5 (in effect since January 1, 2026) and the school fee guidance in the state housing department’s March 2026 ADU Handbook:
| Situation | What state law says |
|---|---|
| ADU of 750 sq ft of interior livable space or less (JADU of 500 or less) | No impact fees from a city, county, special district or water corporation |
| ADU over 750 sq ft | Impact fees allowed, proportional to the main home’s square footage |
| School fees | Exempt under 500 sq ft of interior livable space; above that, districts may charge them but do not have to |
| Conversion of existing space | No new separate connection, connection fee or capacity charge (unless built with a new home or sold separately) |
| New detached ADU | A separate connection can be required, at a proportionate fee capped at the reasonable cost of service |
| Building permit, plan check and review fees | Not impact fees, so not waived |
Two details matter. Exactly 750 sq ft is now covered, though some older city pages still say “less than 750.” And because “impact fee” excludes permit processing fees (Government Code section 66000), the waiver never touches your building permit or plan check.
Six of our 14 models are 749 sq ft or smaller, priced from $199,000 to $369,000, and two of them, The 405 and the Four Fifty, are also under the 500 sq ft school fee line. Our eight models from 885 to 1,200 sq ft fall in the tier where proportional impact fees can apply.
What “ADU fees” actually covers
“Fees” usually means several charges paid to different agencies:
- Building permit and plan check: set by your city, or the County on unincorporated land, and tied to project size or valuation.
- Impact fees: park, traffic and similar facility fees, waived at 750 sq ft or less. See our ADU impact fees guide.
- School fees: set by your school district under Education Code 17620; the district certifies the fee is paid, or does not apply, before the permit is issued.
- Fire review: plan review by the fire agency, plus sprinkler permits where required.
- Water, sewer and septic: set by your providers within the state limits above, or by the County’s Department of Environmental Health on septic parcels.
City or county: who sets your fees
Most Santa Clara County homes sit inside a city, like San Jose, Morgan Hill, Gilroy, Los Gatos, Los Altos, Sunnyvale and Mountain View. Inside city limits, the city issues your permit under its own fee schedule; the County’s schedule covers only unincorporated land. That is why our Santa Clara County ADU rules guide goes city by city, and why we confirm jurisdiction from parcel records, not a mailing address. For the county-wide picture, see our Santa Clara County ADU regulations overview.
San Jose shows what a city schedule looks like. Its ADU FAQ says ADU size determines the building permit fee, offers a Building Fee Estimator, and lists school fees and location-based parkland fees (both of which, the FAQ says, do not apply to ADUs under 750 sq ft), and as-needed fees for geologic hazard clearance, tree removal and fire variances. See what an ADU costs in San Jose, or start with your city page: San Jose, Morgan Hill or Gilroy.
Unincorporated Santa Clara County fees
Outside every city’s limits, the County of Santa Clara’s Department of Planning and Development issues the permit. For zoning, lot types and the full pre-approved plan rules, see our unincorporated Santa Clara County ADU guide. Based on the County’s ADU page and its published fee schedules:
- Building permit fees follow your valuation. The County bases them on a percentage of construction valuation, and its schedule effective July 18, 2026 adds plan check and mechanical, plumbing and electrical permits as percentages of the building permit fee.
- The valuation has to be realistic. County guidance says it covers the total value of the work, including labor, profit and overhead, but not permit, financing or design fees. If the building official considers it too low, the permit can be denied until detailed estimates support it.
- Clean plans save money. Plan reviews beyond three completed rounds are billed hourly.
- Fire and school fees are separate. The County notes that fire and school impact fees are paid separately to those agencies. Its Fire Marshal’s Office keeps its own schedule.
- Pre-approved plans lower review cost. The County’s free plans (an 800 sq ft two-bedroom and a 1,200 sq ft three-bedroom) are charged the minimum two-hour plan review fee when used unchanged. Both are listed above 750 sq ft, so proportional impact fees can apply, depending on the plan’s interior livable space.
- The ordinance is being updated. The County is amending its ADU ordinance to reflect state law, with a Board of Supervisors hearing scheduled for the first quarter of 2027. State fee rules apply in the meantime.
Septic, wells and hillside lots
Unincorporated parcels, from San Martin to the hills above the valley floor, are more likely than city lots to sit on septic, a well or a slope, each adding cost unrelated to impact fees.
- Septic. The County’s Department of Environmental Health reviews septic work under its own fee schedule, and adding an ADU can mean evaluating or upgrading the existing system. See our ADU septic guide.
- Wells and slopes. A private well raises water supply questions a city connection does not, and hillside sites can add grading, drainage or engineering work. We check both early.
- Hazard zones. Expedited pre-approved review, and its minimum fee, is not available in the Wildland Urban Interface, a special flood hazard area or a geologic hazard zone.
This site work is property-specific: we scope it in the feasibility study, and it can sit outside the model price, though our team still handles it.
How Framework First pricing handles fees
Every Framework First ADU is priced all-inclusive: $199,000 to $599,000 across 14 models from 405 to 1,200 sq ft, with a permitting budget alongside plans, foundation, the factory build, crane delivery, utility hookups, appliances and final inspection. Each home is built about 97% off-site in our Salinas factory, and our team handles the permit process from application to final inspection.
Because several agencies set your fees, we never quote one from memory. The feasibility study ($497 standard, $997 empty lot) confirms your jurisdiction, fees and site work before you sign. It is refunded in full, minus payment processing fees, if your property cannot host an ADU, and credited toward your build if you sign with us within 90 days. Compare models and pricing to see which side of the 750 sq ft line fits your plans.
Frequently asked questions
Are ADU fees the same in every Santa Clara County city?
No. Each city sets its own building permit, plan check and local fees, and unincorporated land follows the County’s schedule. State law stays the same everywhere: no impact fees at 750 sq ft or less, proportional fees above, and the same water and sewer limits. School fees depend on your school district.
Which Framework First models avoid impact fees?
Six of our 14 models are 749 sq ft or smaller, so no city, county or special district impact fees apply: Four Fifty, The 405, Five Five Five, Six Sixty, Six Sixty Duo and Seven Forty-Nine. The 405 and Four Fifty are also under the 500 sq ft school fee line. Our 885, 945 and 1,200 sq ft models can be charged proportional impact fees, and building permit fees apply at every size.
Do I pay school fees on an ADU in Santa Clara County?
It depends on size and your district. Under 500 sq ft of interior livable space, no. Above that, the state housing department’s handbook says school districts may charge school fees but do not have to, and some city guidance, including San Jose’s ADU FAQ, says school fees do not apply below 750 sq ft. The district certifies its fee is paid or does not apply before the permit is issued. More in do ADUs pay school fees.
Does the county charge a separate fire fee?
On unincorporated land, yes. The County Fire Marshal’s Office charges for fire, life and safety review based on valuation, plus residential sprinkler permits where required. Fire impact fees follow the same 750 sq ft rule; review fees do not. Inside a city, the fire agency that serves that city reviews plans. That is the San Jose Fire Department in San Jose, and the Santa Clara County Fire Department in cities it serves, such as Los Gatos, Los Altos, Cupertino, Campbell and Saratoga. San Jose can require a fire variance, with its own fee, when an ADU sits far from the street or a hydrant.
Will I need a separate water or sewer connection, and what does it cost?
It depends on the ADU. A conversion inside your home or an existing accessory structure cannot be required to take a new connection or pay a related fee, unless it is built with a new home or sold separately. A new detached ADU can be required to connect separately, at a fee proportionate to its size or plumbing fixtures and capped at the reasonable cost of service. Your provider sets the number, and we confirm it for your parcel.
Is there a Santa Clara County ADU fee calculator?
The County’s ADU page links to a cost calculator from Baird+Driscoll Community Planning and the Chan Zuckerberg Initiative, a non-government group. The County warns it is a rough estimate that leaves out fire and school impact fees, and San Jose offers its own Building Fee Estimator. Neither replaces a parcel-specific check.
Want the real fee picture for your parcel instead of a general range? Start a feasibility study and our team will confirm your jurisdiction, your fees and your site work before you sign.
