ADU fees in Campbell: $9,824–$15,941 in modeled fees for 1,000 sq ft, plus valuation-based permits
Campbell prices its building permit at 2% of construction valuation, so most of the permit cost depends on your project. ADUs of 750 sq ft or more pay a park in-lieu fee, prorated under state law and capped at $9,328 per ADU in the FY 2026-27 schedule. Planning's post-entitlement review of a detached ADU is $259.
14 fee lines · 2 official sources · checked Oct 18, 2026 · Sources · Calculator
Totals leave out valuation-based building fees. Enter a construction valuation in the calculator to include them.
Modeled fees by ADU size
Detached ADU, 2,000 sq ft main home (example assumption), law in force today. Bars: solid = fees that apply, hatched = fees that may apply.
Each fee with its official source (numbers link to the source list). Est. = computed by us from the official rate; May apply = high total only; Up to = statewide cap, district may charge less.
Building permit (2% of valuation up to $500,000)1Tiered: 2.00% of the first $500,000 of valuation, 1.66% of the next $500,000, 1.00% above. Minimum $237. Campbell doesn't publish a valuation per sq ft, so enter your valuation in the calculator.
Strong motion instrumentation (state, 0.013% of valuation)1
Needs valuation
Needs valuation
Needs valuation
Needs valuation
Address addition1Per new address; ask the City whether your ADU needs one.
May apply$237
May apply$237
May apply$237
May apply$237
Construction taxes
Construction license tax ($0.50 per sq ft)1Campbell Municipal Code 3.40. We haven't confirmed whether it applies to ADUs, so it counts in the high total only.
May apply$250
May apply$375
May apply$500
May apply$600
Impact fees
Park in-lieu fee (ADU 750 sq ft or larger)1Prorated from the $33,025 single-family fee by ADU ÷ main-home size, as the schedule's note requires ("calculated per State law"), and capped at the $9,328 ADU maximum.
Exempt
Exempt
Est.$9,328
Est.$9,328
Roadway maintenance fee (0.32% of valuation)1Listed with Campbell's in-lieu/impact/mitigation fees, so we treat it as an impact fee: $0 at 750 sq ft or less.
Exempt
Exempt
Needs valuation
Needs valuation
School district fee
School fees (Campbell Union / Campbell Union High, or your district)3District rates not captured yet; shown at the 2026 statewide Level 1 maximum as an upper bound.
Exempt
Up to$4,035
Up to$5,380
Up to$6,456
Modeled total
$496–$982
$496–$5,143
$9,824–$15,941
$9,824–$17,117
Junior ADUs
Campbell's park in-lieu fee for a junior ADU is $0. 1
Rules
What you can build in Campbell
Maximum size
Detached: 1,200 sq ft. Attached: 50% of the existing home, but at least 1,000 sq ft is allowed. By-right detached ADU on a single-family lot: 800 sq ft. 2
Height
Detached: 20 ft (18 ft and one story on historic properties). Attached: same as the main home's standard. 2
Setbacks
4 ft rear and side; front setback as for the property. 10 ft from the main home when in front of or behind it, 5 ft when beside it. 2
Parking
None required, and parking removed for a garage conversion doesn't have to be replaced. 2
Owner occupancy
Not required for an ADU. For a JADU, the JADU or the house must be owner-occupied. 2
Pre-approved plans
State law: every city must run a program to pre-approve ADU plans (Gov. Code 65852.27). Local rule not captured yet.4
State law
Why a 750 sq ft ADU pays no impact fees
California bars impact fees on ADUs of 750 sq ft or less of interior livable space. Above that, they must be proportional to the main home’s size; we assume 2,000 sq ft unless you enter yours. School fees start at 500 sq ft. From January 1, 2027, SB 1117 limits impact fees to the area over 750 sq ft. How the state rules work →
ADU permits issued
Campbell issued 340 ADU building permits in 2025
1,182 from 2018 to 2025, as the jurisdiction reported to the state in its Housing Element Annual Progress Reports (Table A2, ADU rows; may include JADUs). “–” means no ADU rows were reported that year.
Building permit fees are a percentage of construction valuation; Campbell doesn't publish a valuation per sq ft, so modeled totals leave them out. Enter a valuation in the calculator.
Storm drain area fees are charged per acre ($2,120 per acre in R-1) and depend on the lot; whether an ADU triggers them isn't stated.
Trade permits (plumbing, electrical, mechanical: $237 base each), the state building standards fee and sewer/water connection charges from the sanitation district and water company aren't included.
School district rates not captured; shown at the statewide cap.
The Governor approved SB 1117 (Chapter 809, Statutes of 2026) on September 29, 2026. It amends Gov. Code 66311.5: on lots with up to two ADUs, impact fees on an ADU over 750 sq ft must still be proportional to the primary home, and may only be charged on the area over 750 sq ft. Regular 2026 statutes take effect January 1, 2027. Until then, fees on a larger ADU are figured on its full size. Our calculator has a 2027 setting that shows the difference.
The Department of Housing and Community Development updated its ADU Handbook to reflect the laws that took effect January 1, 2026. Its proportional-fee example: a 1,000 sq ft ADU next to a 2,000 sq ft home pays 50% of the fee a new home would pay. Our models use 2,000 sq ft as the example primary-home size unless you enter your own.
On January 28, 2026 the State Allocation Board raised the statewide maximum Level 1 developer fee for residential construction from $5.17 to $5.38 per sq ft (+4.06%). School districts collect it on ADUs of 500 sq ft or more, at their own adopted rate up to this cap (higher Level 2/3 fees need extra findings). Where we haven't confirmed a district's rate, we use $5.38 as the upper bound.
SB 543 (Chapter 520, Statutes of 2025) took effect January 1, 2026. It restates the impact-fee rule in Gov. Code 66311.5: no impact fees on an ADU of 750 sq ft of interior livable space or less, or a JADU of 500 sq ft or less; above that, fees must be proportional to the primary home. It also caps JADUs at 500 sq ft of interior livable space. Many city documents still cite the older section numbers (65852.2 or 66324).
For a detached ADU with a 2,000 sq ft main home (an example assumption), our model of Campbell’s official fee schedules comes to $496–$5,143 at 750 sq ft and $9,824–$15,941 at 1,000 sq ft. These totals leave out valuation-based building fees. Ranges show fees that may or may not apply to your project.
Does Campbell charge impact fees on a 750 sq ft ADU?
No. California Government Code section 66311.5 bars impact fees on an ADU of 750 sq ft of interior livable space or less (500 sq ft or less for a JADU). Above 750 sq ft, impact fees must be proportional to the size of the main home. At 1,000 sq ft, the impact fees we model for Campbell come to at most $9,328.
Do school fees apply to an ADU?
Only at 500 sq ft or more. School districts charge their adopted developer fee per sq ft, capped at the State Allocation Board’s Level 1 maximum ($5.38 per sq ft since January 28, 2026) unless they qualify for higher levels.
How big can an ADU be in Campbell?
Detached: 1,200 sq ft. Attached: 50% of the existing home, but at least 1,000 sq ft is allowed. By-right detached ADU on a single-family lot: 800 sq ft.
A local agency, special district, or water corporation shall not impose any impact fee upon the development of an accessory dwelling unit that has 750 square feet of interior livable space or less