ADU fees in Monterey County: $0–$5,380 in modeled fees for 1,000 sq ft, plus valuation-based permits
In unincorporated Monterey County, a new ADU up to 750 sq ft gets a reduced plan check fee: 32.5% of the building inspection fee instead of the usual 65%. Both are set from construction valuation, which the County takes from the ICC valuation tables. Enter your valuation to see the permit lines; area-specific traffic and park fees aren’t modeled.
6 fee lines · 1 official sources · checked Oct 18, 2026 · Sources · Calculator
Totals leave out permit fees until you enter a construction valuation, and area-specific impact fees and valuation-based building fees and plan check: new adu up to 750 sq ft, plan check: adu over 750 sq ft at some sizes. 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.
Fee
499 sq ft
750 sq ft
1,000 sq ft
1,200 sq ft
Planning & zoning
General Plan Management Fee115% of the permit fee; we apply it to the building inspection fee.
Needs valuation
Needs valuation
Needs valuation
Needs valuation
Building permit & plan check
Building inspection (valuation table)1Single-family new construction rows: base for the valuation range plus the increment per $1,000 or fraction above it. The County values construction from the current ICC Building Valuation Data; enter your valuation.
Needs valuation
Needs valuation
Needs valuation
Needs valuation
Plan check: new ADU up to 750 sq ft (32.5%)132.5% of the building inspection fee for a new ADU up to 750 sq ft.
Needs valuation
Needs valuation
n/a
n/a
Plan check: ADU over 750 sq ft (single-family rate, 65%)1The reduced ADU rate is only for ADUs up to 750 sq ft; above that we apply the single-family plan check rate of 65%.
n/a
n/a
Needs valuation
Needs valuation
Technology Fee113% of the permit fee; we apply it to the building inspection fee.
State floor: cities must allow at least 850 sq ft (1,000 sq ft with 2+ bedrooms); detached ADUs can be capped at 1,200 sq ft. Local rule not captured yet.3
Height
State floor: 16 ft detached (18 ft near transit or on a multifamily lot, +2 ft for roof pitch); 25 ft attached. Local rule not captured yet.3
Setbacks
State limit: no more than 4 ft side and rear. Local rule not captured yet.3
Parking
State limit: at most 1 space per ADU or bedroom, and none within ½ mile of transit and in other cases. Local rule not captured yet.3
Owner occupancy
State law: cities can't require the owner to live on site for an ADU (JADUs: owner on site if sanitation is shared). Local rule not captured yet.3
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.3
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 apply only above 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
Monterey County issued 61 ADU building permits in 2025
283 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 inspection and plan check depend on valuation; the County uses the ICC Building Valuation Data, which we don’t reproduce. Enter your own valuation.
Area-specific traffic impact fees, the TAMC regional fee, park (Quimby) fees, Environmental Health septic/well reviews and Water Resources Agency fees aren’t modeled.
Planning or coastal permits, where an ADU needs one, aren’t included. The Standardized ADU Plan Review option ($646) isn’t shown.
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 Monterey County’s official fee schedules comes to $0–$4,035 at 750 sq ft and $0–$5,380 at 1,000 sq ft. These totals leave out permit fees until you enter a construction valuation, and area-specific impact fees and valuation-based building fees and plan check: new adu up to 750 sq ft, plan check: adu over 750 sq ft at some sizes. Ranges show fees that may or may not apply to your project.
Does Monterey County 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.
Do school fees apply to an ADU?
Only above 500 sq ft. 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.
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