How is an ADU building permit fee calculated in California?

Three models exist. Valuation-based cities (Pasadena, Campbell) charge a percentage of your declared construction cost — Campbell charges 2.00% on the first $500,000 of valuation plus 33% of that for plan check. Flat-fee cities (Fontana $3,195; Chula Vista $3,951 for detached ADUs using standard plans) charge one number regardless of cost. Per-square-foot cities (Oceanside, ~$7,541 on 800 sq ft) charge by area. The model matters more than the rate: a valuation-based permit punishes expensive finishes, a flat fee rewards them.

Which California city has the cheapest ADU permit?

Of the cities in our series, Riverside at $1,006 (verified from the city's fee schedule) is the lowest we have published. Fontana's $3,195 flat fee and Chula Vista's $3,951 ADU-only flat fee are the most predictable — you know the number before you design anything.

What is plan check and is it included in the permit fee?

Plan check is the city's engineering review of your drawings, and it is usually a separate line item — often 33–65% of the base permit fee. Campbell charges plan check at 33% of the permit fee. Some cities bundle it (Chula Vista's $3,951 includes intake, plan check, and inspection). Always ask whether a quoted permit number includes plan check or not.

Valuation vs Flat vs Per-Sq-Ft: How Cities Actually Price Your ADU Permit

Published: 20 Oct 2026 · Last verified: 20 Oct 2026 · Next review: Jan 2027

Every California city charges you for the same building permit. Almost none of them calculate it the same way.

There are three pricing models in use across the cities in this series — valuation-based, flat-fee, and per-square-foot — and the model your city uses changes your incentives more than the rate itself. A valuation-based permit taxes expensive finishes. A flat fee rewards them. A per-square-foot schedule punishes size but ignores cost.

Here is how each model works, with real numbers from published fee schedules.

Model 1: Valuation-based — the percentage tax on your budget

Cities: Pasadena, Campbell (and most California cities by default)

The city takes your declared construction valuation — what you say the project costs to build — and charges a percentage of it.

Campbell publishes the clearest version (FY 2026 Master Fee Schedule, Resolution 13279):

First $500,000 of valuation: 2.00%
$500,001–$1,000,000: 1.66%
Over $1,000,000: 1.00%
Plan check: 33% of the permit fee, charged at permit issuance
Plus: General Plan maintenance (0.16% of valuation), technology fee (0.04%), training (0.02%), Construction License Tax ($0.50/sq ft), Title 24 plan check ($232), and state surcharges

On an 800 sq ft ADU with a $100,000 declared valuation (an illustrative assumption, not a city-published figure): permit ≈ $2,000 + plan check $660 + the add-ons ≈ $3,529 including the $400 construction tax.

Pasadena also uses valuation (“based on project valuation… calculated using current cost of construction,” per the FY 2019 staff report), but publishes no per-square-foot table — the city computes your number from your valuation. What Pasadena does publish: estimated permit + plan check for each of its four pre-approved ADU designs, from $7,000 (374 sq ft studio) to $13,000 (682 sq ft 2BR).

The incentive: valuation-based permits punish expensive finishes. Upgrade from laminate to quartz and your permit fee rises. Declare a higher valuation honestly and you pay more than the neighbor who lowballs — which is why cities audit valuations against their own cost tables.

Model 2: Flat-fee — one number, no math

Cities: Fontana ($3,195), Chula Vista ($3,951–$4,963)

Fontana charges $3,195 flat for an ADU building permit (confirmed from the city’s fee schedule). No valuation declaration, no percentage, no square-foot multiplier. You know the number before you draw a single line.

Chula Vista goes further with an ADU-only flat schedule (Fee Bulletin 10-400, September 2024) — the most transparent in our series:

Detached ADU using City Standard Plans: $3,951 ($476 intake + $533 plan check + $2,942 inspection)
Detached ADU, custom design: $4,963
Attached ADU, first story: $2,380 for the first 300 sq ft + $423 per additional 300 sq ft
Garage conversion to ADU: $1,604 for the first 400 sq ft + $158 per additional 400 sq ft

An 800 sq ft detached ADU on Chula Vista’s standard plans costs $3,951 all-in — intake, plan check, and inspection bundled. No surprises.

The incentive: flat fees reward expensive finishes and punish nothing. The quartz upgrade costs you $0 extra in permit fees. The tradeoff: small, cheap ADUs subsidize large, expensive ones.

Model 3: Per-square-foot — pay by the area

Cities: Oceanside (~$7,541 on 800 sq ft)

Editor’s note (21 Oct 2026): The Oceanside figures in this section are under review. They rest on 2018/2021-vintage rate tables — the city publishes no current FY rate table — and our Oceanside breakdown documents a separate open conflict between the city’s ADU impact-fee exemption ordinance and an August 2025 draft fee study. Treat the ~$7,541 as a partial, dated figure until the review completes.

Oceanside uses area-based plan check and inspection tables for new residential construction. On the “Custom or Model Homes” row at 1,000 sq ft (the bracket covering 800 sq ft):

Plan check base: $1,862.70
Inspection base: $3,515.40
Fire plan check + inspection (20% of building): $1,075.62
Water plan check (15% of building): $279.41
Plus 10% General Plan surcharge and 2% technology surcharge
Total: ≈ $7,541

That is the highest permit number in our series — roughly double Chula Vista’s flat fee — on a rate table adopted in 2018 (plan check) and 2021 (miscellaneous). Whether Oceanside classifies a detached ADU under the “Custom Homes” row or the cheaper “Residential Addition” row ($2,522.34) is not confirmed in any published document; we have marked it as such.

The incentive: per-square-foot schedules punish size but ignore cost. Build small with expensive finishes and you win. Build large with cheap finishes and you lose.

The comparison

Model	Example cities	800 sq ft ADU permit	Predictability
Valuation-based	Pasadena, Campbell	$3,529–$13,000 (varies)	Low — depends on your declared cost
Flat-fee	Fontana, Chula Vista	$3,195–$4,963 (fixed)	High — one number
Per-square-foot	Oceanside	~$7,541	Medium — depends on classification

The spread on the same 800 sq ft ADU: $3,195 to ~$7,541 — a $4,346 gap from the pricing model alone, before a single impact fee or school fee is added.

How to read your city’s fee schedule

Find which model your city uses. Search the fee schedule for “valuation,” “flat,” or “per square foot.” If the schedule lists percentages, it is valuation-based.
Ask whether plan check is included. It is usually 33–65% on top of the base permit. Chula Vista bundles it; most cities do not.
Ask about surcharges. Oceanside adds 12% in surcharges. Campbell adds five separate line items. The headline rate is never the total.
If valuation-based, ask how the city verifies your declared valuation. Most cities compare against ICC valuation tables. Under-declaring risks a correction mid-review.
Check for ADU-specific rows. Chula Vista and Torrance publish ADU-only fees. Most cities do not — your ADU is priced as generic residential construction.

The bottom line

The permit is the smallest of the big three soft costs (permit, school fees, impact fees), but it is the one you encounter first — and the pricing model tells you how your city thinks. Valuation-based cities tax your budget. Flat-fee cities sell you certainty. Per-square-foot cities tax your floor plan.

None of the models is inherently fair. But only one of them lets you know the price before you start.