Monterey County ADU Requirements (2026)
Size limits, setbacks, required documents, and fees for building an ADU in Monterey County, California — covering unincorporated county areas and key city differences.
Overview
Monterey County spans from the Salinas Valley to Big Sur, with a mix of urban, agricultural, and coastal properties. ADU rules follow California state standards, but certain areas have overlay requirements — particularly the Coastal Zone — that add review steps.
This guide covers ADU requirements for unincorporated Monterey County. If your property is within an incorporated city (Salinas, Monterey, Pacific Grove, Seaside, Marina, etc.), contact that city's planning department.
Jurisdiction and overlay zones
| Zone | What it means for your ADU |
|---|---|
| Standard residential | State ADU rules apply directly |
| Coastal Zone | Additional Coastal Development Permit may be required |
| Agricultural | ADU eligibility depends on existing legal dwelling status |
| Fort Ord | Fort Ord Reuse Authority (FORA) requirements may apply |
Check your property's zoning designation on the Monterey County GIS portal before starting your ADU project.
Size limits
| ADU type | Maximum size |
|---|---|
| Detached ADU | Up to 1,200 sq ft |
| Attached ADU | Up to 50% of existing living area, or 1,200 sq ft — whichever is less |
| JADU (Junior ADU) | Up to 500 sq ft, within existing structure |
| Garage conversion | Full existing garage area |
A single-family property may have both one ADU and one JADU.
Setback requirements
| Setback | Requirement |
|---|---|
| Side and rear | 4 ft minimum (state law, new construction) |
| Front | Per underlying zoning district |
| Conversion of existing structure | No additional setback required |
| Height | 16 ft for detached ADU (state minimum allowance) |
Properties in the Coastal Zone may face additional setback or height requirements from the Local Coastal Program.
Required documents
- Building permit application — Monterey County HCD form
- Site plan — property boundaries, setbacks, existing and proposed structures, access, parking
- Floor plan — dimensioned with room labels, fixtures, egress, accessibility
- Elevations — all sides, materials, heights, roof pitch
- Structural plans — foundation, framing, lateral force resistance (Seismic Design Category D)
- Title 24 energy compliance — CF1R forms
- CalGreen checklist — mandatory green building measures
- Proof of ownership — deed or title report
- Coastal Development Permit application — if within the Coastal Zone
For properties on septic systems, include a septic evaluation demonstrating capacity for the additional dwelling.
Fees
California limits ADU fees:
- No impact fees for ADUs under 750 sq ft
- Proportional impact fees for ADUs 750 sq ft and above
- No school fees for ADUs
Monterey County building permit fees are based on project valuation. As of 2026, expect:
- Building permit fee: $2,000–$5,000 depending on scope
- Plan check fee: Typically 65% of permit fee
- Coastal Development Permit: Additional fee if applicable
Coastal Zone considerations
If your property is within the Coastal Zone (roughly Highway 1 corridor and coastal areas):
- A Coastal Development Permit (CDP) may be required in addition to the building permit
- Review timelines are longer due to the additional permit layer
- Height and setback restrictions from the Local Coastal Program may be stricter than state minimums
- Visual resource policies may affect exterior materials and colors
- ESHA (Environmentally Sensitive Habitat Area) buffers may limit building location
Check with Monterey County Housing & Community Development to confirm whether a CDP is required for your parcel.
Common rejection reasons
- Missing setback dimensions on site plan
- No Title 24 energy forms included
- Incomplete structural details for Seismic Design Category D
- Coastal Zone requirements not addressed (for applicable parcels)
- Site plan missing north arrow, scale, or utility connections
- No construction type or occupancy stated on cover sheet
Sources
Frequently asked questions
Yes. Under California state law, property owners with existing single-family or multifamily residential properties can build at least one ADU. This applies to both unincorporated Monterey County and the incorporated cities (Salinas, Monterey, Pacific Grove, etc.), though each jurisdiction has its own permitting process.
Monterey County follows state minimum ADU standards. Some areas may have additional considerations due to the Coastal Zone overlay, agricultural land use designations, or the Fort Ord Reuse Plan. Properties in the Coastal Zone may require a Coastal Development Permit in addition to the building permit.
Properties zoned for agriculture may be eligible for farmworker housing or agricultural employee housing under different provisions. ADU rules apply to residentially-zoned parcels. If your property is zoned agricultural but has an existing legal dwelling, contact the County Housing office to confirm ADU eligibility.
California law requires the local agency to act on a complete ADU application within 60 days. Monterey County's actual timelines vary based on plan completeness, whether the property is in the Coastal Zone (additional review layer), and current application volume. Submitting complete, error-free plans is the best way to avoid delays.
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