Local zoning · Sonoma County

Sonoma County — Overlay Districts

Overlay Districts under the Sonoma County local zoning and planning code, with the controlling citations.

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Last reviewed: July 6, 2026

Overview

In unincorporated Sonoma County, “overlay” zoning appears in the code as combining districts layered on top of a base zone in Chapter 26 (Zoning) of the Sonoma County Code. Overlays never replace the base zone; they add standards, limits, or review requirements tied to site resources, hazards, mobility, or policy priorities. The County’s official list of combining districts is in § 26-02-100, and parcel-specific overlay flags are maintained in the official zoning database (§ 26-02-130).

The big rule: an overlay (combining district) adds to your base zoning; it doesn’t erase it. Always verify overlay flags in the County’s official zoning database before designing a project (§ 26-02-130).

Related reading: see the countywide context at the zoning & planning overview, how base districts work in Sonoma County Zoning, dimensional rules in Sonoma County Development Standards, project review in Sonoma County Design Review, parking rules in Sonoma County Parking, historic procedures in Sonoma County Historic Preservation, how existing uses are treated in Sonoma County Nonconforming Uses, and relief routes in Sonoma County Variances and Exceptions.

What overlays exist?

The County enumerates combining districts (overlays) in § 26-02-100, which include but are not limited to: S, F1, F2, AH, RE, LG, SR, RC, BH, VOH, HD, G, MR, Z, X, B, and TS. Additional combining districts appear elsewhere, including VR (Visitor Residential) in Article 77 and WH (Workforce Housing) in Article 75; the PF zone can also function as a combining district for future public facilities. Always confirm live applicability in the zoning database (§ 26-02-130).

S — Study Combining District (Article 54)

  • Purpose and where it applies: Temporary overlay used while the County studies an area; it supplements all other zoning during that period. Projects still must follow the base zone plus any S-conditions.
  • Typical permitted uses: One single-family dwelling, home occupations, and accessory/agricultural uses by right; other uses require a use permit (§§ 26-54-010, -020).
  • Key standard: S provisions are “combining in nature” and time-limited; at study conclusion they cease for the rezoned area. Verify any ordinance establishing S for your site.

F1 — Floodway Combining District (Article 56)

  • Purpose/where: Applied to mapped floodways (FEMA); protects life/property from floodway risks (§§ 26-56-005, -010).
  • Uses: No new permanent structures or structures intended for human occupancy in the floodway (§ 26-56-020). Temporary items like docks may need a use permit (§ 26-56-030).
  • Key standards: “Zero net fill” in the Laguna de Santa Rosa floodways (§ 26-56-030(c)); County may require technical studies (§ 26-56-030(b)).

F2 — Floodplain Combining District (Article 58)

  • Purpose/where: Applied to the 100‑year flood hazard area per FEMA (§ 26-58-010).
  • Uses: Same as base zone but must meet floodplain standards (§ 26-58-020).
  • Key standards: Construction must meet County flood protection regulations (Chapter 7B) (§ 26-58-030(a)); subdivisions allowed only if filled to selected flood profile (§ 26-58-030(c)); “zero net fill” applies within the Laguna de Santa Rosa (§ 26-58-030(d)).

AH — Affordable Housing Combining District (Article 59)

  • Purpose/where: Implements Housing Element to enable lower‑income rental housing in urban service areas (§ 26-59-005).
  • Uses: Adds all‑affordable multifamily (16–24 du/ac) plus related accessory uses (§ 26-59-010).
  • Key standards: Must meet R3 design/development criteria and execute an affordable housing agreement; design review is required (§ 26-59-020).

RE — Renewable Energy Combining Zone (Article 60)

  • Purpose/where: Flags areas appropriate for large-scale renewable energy; may be combined only with listed base zones (LEA, DA, RRD, TP, C3, M2, PF) (§§ 26-60-005, -010).
  • Uses: Adds certain renewable energy facilities as permitted with a zoning permit (§ 26-60-030).
  • Key standards: Not allowed with LIA or any residential zones and not within 300′ of them; excludes mapped scenic/biotic/historic areas unless protective easements are recorded (§ 26-60-020).

LG — Local Guidelines Combining District (Article 63; see Article 90 for subarea standards)

  • Purpose/where: Identifies parcels subject to adopted Local Area Guidelines and Standards (§§ 26-63-005 to -030; § 26-90-030).
  • Uses: Same as base zone, but design/site plan review is required for exterior work unless a listed exemption applies (§ 26-90-040). Subareas include Canon Manor West, Glen Ellen, Hwy 116 Scenic Corridor, Penngrove Main Street, Russian River Corridor, Sebastopol Rd Urban Vision, The Springs Hwy 12, Taylor/Sonoma/Mayacamas Mountains, and Lance Drive (§ 26-63-030; §§ 26-90-050 to -130).
  • Key standards: Subarea guidelines control if they conflict with general code; check the Zoning Database suffix (e.g., LG/GE2). § 26-90-040.

SR — Scenic Resources Combining District (Article 64)

  • Purpose/where: Preserves scenic character; applies to mapped scenic landscapes and community separators (§ 26-64-005).
  • Uses: Base-zone uses continue; hillside siting/screening and infrastructure placement rules apply in designated areas (§ 26-64-020).
  • Key standards: Site below ridgelines and use natural landforms/vegetation to screen; underground utilities where practical (§ 26-64-020). Design review applies to development projects (§ 26-64-050).

RC — Riparian Corridor Combining Zone (Article 65)

  • Purpose/where: Protects riparian habitat along designated streams; includes the stream bed/bank and a streamside conservation area measured from the top of the higher bank; zoning database shows corridor width and ag setback (e.g., RC 100/50) (§§ 26-65-005, -010, -020).
  • Uses: Most development is prohibited in the stream channel/streamside area unless allowed by § 26-65-040 or granted an exception per § 26-65-030. Examples include restoration, road/utility crossings, fencing, and limited agriculture with setbacks (§ 26-65-040).
  • Key standards: Agricultural cultivation setbacks are 100′ (Russian River 200′ corridor), 50′ (100′ corridor/uplands of 50′ corridors), or 25′ (all other corridors) (§ 26-65-040.H.2).

BH — Biotic Habitat Combining Zone (Article 66)

  • Purpose/where: Applied to mapped Biotic Habitat Areas in the General Plan or area/specific plans (§§ 26-66-005, -010).
  • Uses: Base-zone uses continue; the County may require a biotic assessment for discretionary projects; tentative maps must set envelopes away from habitat; 50′ wetland setback with specified exceptions (§ 26-66-020).

OAK and VOH — Oak Woodland and Valley Oak Habitat Combining Districts (Article 67)

  • Purpose/where: Countywide oak protections updated in 2024; applies to entire parcels that intersect the VOH zone or contain ≥0.5 acre of mapped Oak Woodland (§ 26-67-020(2)). Prohibits oak woodland “type conversion” except as allowed through discretionary review with findings/mitigation (§ 26-67-010; § 26-67-070).
  • VOH tree removal: Removing a valley oak >6″ DBH requires a zoning permit and mitigation at 1.5× the tree-protection ratios (or in‑lieu fee); ≥36″ DBH removals require a use permit (§ 26-67-090).
  • Design review tie-in: Projects already subject to design review must landscape with at least 50% valley oaks in VOH areas (§ 26-67-100). Penalties for knowing violations increase mitigation fivefold (§ 26-67-110).

HD — Historic Combining District (Article 68)

  • Purpose/where: Protects designated historic structures and districts (§§ 26-68-005, -010).
  • Uses/approvals: Exterior alterations, demolition, and new buildings in an HD district require approval by the County Landmarks Commission; minor alterations may be approved by staff where guidelines allow (§ 26-68-020). Conformance with adopted district guidelines (Bodega, Freestone, Occidental) is required (§ 26-68-025).

G — Geologic Hazard Area Combining District (Article 70)

  • Purpose/where: Applied within Alquist‑Priolo special studies zones; reduces seismic/landslide risks (§§ 26-70-005, -010).
  • Uses: Base-zone uses continue, but you cannot place a structure intended for human occupancy across or within 50′ of an active fault (§ 26-70-020). Geologic reports are required (§ 26-70-030).

MR — Mineral Resource Combining District (Article 72)

  • Purpose/where: Conserves land for future mineral production; typically combined with agricultural/resource base zones consistent with the Aggregate Resources Management Plan (§ 26-72-005).
  • Uses: Mining allowed with a surface mining use permit and reclamation plan; certain agriculture/timber activities allowed; agricultural cultivation near riparian corridors is limited (100′/50′/25′) (§ 26-72-010). Development criteria set lot yards/heights and defer to plans where more restrictive (§ 26-72-030).

WH — Workforce Housing Combining District (Article 75)

  • Purpose/where: Increases workforce housing near jobs/transit within urban service areas; applied to LC, C2, MP, M3, M1, PF base zones (§§ 26-75-005, -010).
  • Uses: Adds multifamily/mixed-use housing options with specified affordability minimums; prohibits vacation rentals in WH (§§ 26-75-030 to -050).

Z — Accessory Dwelling Unit Exclusion Combining District (Article 76)

  • Purpose/where: Excludes ADUs in areas with water/sewer/fire access or traffic constraints (§ 26-76-005).
  • Uses: Base-zone uses continue, but establishing a new ADU is prohibited (§ 26-76-010). See also ADU applicability and groundwater limits elsewhere in Chapter 26.

VR — Visitor Residential Combining Zone (Article 77)

  • Purpose/where: Can be applied to the K (Recreation and Visitor-Serving Commercial) base zone; allows a mix of residential products (e.g., SRO, resort/condo/time-share) by use permit where compatible (§§ 26-77-005 to -020).
  • Key standards: Development follows base-zone standards; F1/F2 flood restrictions are reaffirmed in § 26-77-030.

X — Vacation Rental Exclusion and Cap Combining District (Article 79)

  • Purpose/where: Used to exclude or cap concentrations of vacation rentals in defined areas (§ 26-79-005).
  • Uses: If “exclusion” applies, new vacation rentals are not permitted; if a “cap” applies (5% or 10% of single-family dwellings), new vacation rentals are disallowed once the cap is met (§§ 26-79-010, -020).

B — B Combining Districts (Article 78)

  • Purpose/where: Sets maximum residential density (B6) or freezes parcels against further subdivision (B7/B8), typically after clustering or due to policy constraints (§§ 26-78-005, -010).
  • Key standards: B6 fixes maximum dwelling density; B7/B8 lots cannot be further subdivided; base-zone yards apply unless otherwise approved (§ 26-78-010).

TS — Traffic Sensitive Combining District (Article 80)

  • Purpose/where: Implements General Plan traffic constraints; limits use intensity by trip caps in areas with congestion (e.g., Sonoma Valley) (§ 26-80-005).
  • Key standards: Example limits—63 trips/acre/PM peak for “limited commercial,” and 18 trips/acre/PM peak for “limited commercial/traffic sensitive” parcels; ITE Trip Generation governs analysis (§§ 26-80-010, -020).

PF — Public Facilities as a Combining District (Article 14)

  • Use as overlay: The PF zone may be applied as a combining district to signal where future public facilities may be needed; development otherwise follows the base zone, and the County may require contributions to facilities identified in the General Plan (§ 26-14-020.5).

Fast-glance overlay rules that often decide feasibility

Overlay What it does in practice Typical “gotcha” standard Code Reference
F1 Floodway protection No new permanent/habitable structures; “zero net fill” in Laguna floodways § 26-56-020; § 26-56-030(c)
F2 100‑yr floodplain rules Must meet flood regs; subdivisions need fill to flood profile; “zero net fill” in Laguna § 26-58-030(a),(c),(d)
RC Riparian buffers Ag setbacks 100′/50′/25′ depending on corridor; many works need zoning permit § 26-65-040.H.2; § 26-65-040
BH Biotic habitat 50′ wetland setback; building envelopes must avoid habitat § 26-66-020.B–C
SR Scenic resources Site below ridgelines; screen with natural forms; design review required § 26-64-020; § 26-64-050
VOH/OAK Oak resources VOH removals need mitigation; oak woodland conversion tightly limited § 26-67-090; § 26-67-010; § 26-67-070
TS Traffic-sensitive Trip caps (e.g., 63 or 18 trips/acre PM peak) limit build intensity § 26-80-010
Z ADU exclusion ADUs prohibited in mapped Z areas § 26-76-010
AH/WH Affordable/workforce Higher-density multifamily allowed with affordability, design review § 26-59-010; § 26-75-030; § 26-59-020
HD Historic Landmarks Commission approval for exterior work/demolition/new buildings § 26-68-020; § 26-68-025
LG Local guidelines Area-specific design/site plan review required unless exempt § 26-90-040; § 26-63-005–030

Note: Combining zones can modify standard dimensional tables; the code flags this in the development standards articles (e.g., § 26-08-040.B for residential, § 26-10-040.B for commercial).

Checklist

  • Confirm all overlay flags for the parcel in the official zoning database and zoning map layers (§ 26-02-130).
  • Cross-check base zone allowances in Sonoma County Zoning and overlay add‑ons here.
  • If in LG/SR/HD, plan for design review and align with applicable design guidelines (§§ 26-90-040; 26-64-050; 26-68-025).
  • If in RC or BH, map sensitive areas and setbacks; prepare required biotic assessment and streamside conservation compliance (§§ 26-65-010 to -040; 26-66-020).
  • If in VOH/OAK, scope tree inventory and mitigation strategy; anticipate design review landscaping ratios in VOH (§§ 26-67-090, -100).
  • If in F1/F2, confirm FEMA data, “zero net fill” where applicable, and Chapter 7B compliance (§§ 26-56-010 to -030; 26-58-030).
  • If in TS, prepare an ITE-based trip generation and show compliance with parcel trip caps (§ 26-80-010).
  • If in AH/WH, structure affordability, density, and design review commitments (§§ 26-59-010 to -020; 26-75-030 to -050).
  • If in MR, coordinate surface mining permitting and riparian limits (§§ 26-72-010, -030).
  • If in Z or X, verify ADU or vacation rental restrictions before planning those uses (§§ 26-76-010; 26-79-010, -020).

Risks & Ambiguities

Issue Why it matters What to verify
Overlay enumeration vs. current practice The code’s master list shows “X Mixed Occupancy” at Article 77, but Article 77 is now VR; “X” is now Vacation Rental (Article 79). Misreading can misclassify a parcel. Confirm the active overlay article and suffix in the zoning database; use the live articles (§ 26-79-005; § 26-77-005).
Approximate overlay boundaries Floodway/floodplain and RC corridors are shown generally; site-specific determinations can shift limits. For F1/F2 and RC, obtain parcel-level determinations from the County/Water Agency; FEMA sign‑off is required for boundary adjustments (§§ 26-56-010(b); 26-58-010; 26-65-020).
Conflicting overlays Multiple overlays can apply (e.g., SR + RC + BH). Apply the most restrictive overlay and any subarea LG standards; LG expressly controls where it conflicts (§ 26-90-040(c)).
VOH/OAK 2024 updates New countywide rules changed thresholds, mitigation, and penalties. Use Article 67 (2024) for oak/VOH rules (§§ 26-67-010; -020; -090; -100; -110).
Trip caps (TS) vs. base intensity TS can cap intensity far below base-zone allowances. Submit ITE trip generation and show conformance with § 26-80-010.
Design review thresholds Many overlays trigger design review; ministerial exemptions are area-specific. Check overlay article (LG/SR/HD/WH/AH/VR) for review triggers and exemptions (§§ 26-90-040; 26-64-050; 26-68-020; 26-59-020; 26-75-030; 26-77-020).

Plain-English Summary

In unincorporated Sonoma County, overlays are extra rules that sit on top of your base zoning. They can protect rivers and trees, limit building in flood areas, trigger design review, cap traffic, or even prohibit ADUs or vacation rentals in specific neighborhoods. Before you draw plans, pull your parcel’s overlay flags and check the specific article for setbacks, permits, and design standards that will shape what you can build.

Source References

  • § 26-02-100 (Combining districts enumerated); § 26-02-130 (Official zoning database)
  • Article 54: §§ 26-54-010, -020 (S Study combining)
  • Article 56: §§ 26-56-005, -010, -020, -030 (F1 Floodway)
  • Article 58: §§ 26-58-005, -010, -020, -030 (F2 Floodplain)
  • Article 59: §§ 26-59-005, -010, -020 (AH Affordable Housing)
  • Article 60: §§ 26-60-005, -010, -020, -030 (RE Renewable Energy)
  • Article 63: §§ 26-63-005 to -030 (LG Local Guidelines); Article 90 (subarea standards, e.g., §§ 26-90-040 to -110)
  • Article 64: §§ 26-64-005, -010, -020, -050 (SR Scenic Resources)
  • Article 65: §§ 26-65-005, -010, -020, -030, -040 (RC Riparian Corridor)
  • Article 66: §§ 26-66-005, -010, -020 (BH Biotic Habitat)
  • Article 67: §§ 26-67-010, -020, -070, -080, -090, -100, -110 (OAK/VOH)
  • Article 68: §§ 26-68-005, -010, -020, -025, -030, -040 (HD Historic)
  • Article 72: §§ 26-72-005, -010, -030 (MR Mineral Resource)
  • Article 75: §§ 26-75-005 to -050 (WH Workforce Housing)
  • Article 76: §§ 26-76-005, -010 (Z ADU Exclusion)
  • Article 77: §§ 26-77-005 to -030 (VR Visitor Residential)
  • Article 79: §§ 26-79-005 to -020 (X Vacation Rental Exclusion/Cap)
  • Article 80: §§ 26-80-005 to -020 (TS Traffic Sensitive)
  • Article 14: § 26-14-020.5 (PF as combining district)
  • § 26-08-040.B; § 26-10-040.B (combining zones may modify development standards)
  • County overview/context: Sonoma County zoning & planning overview

Sources

Retrieved passages

  • Sonoma County Zoning Code (Section 26-90-070.) Medium relevance
  • Sonoma County Zoning Code (article identifies) Medium relevance
  • Sonoma County Zoning Code (Article 63.) Medium relevance
  • Sonoma County Zoning Code (Chapter 7B) Medium relevance
  • Sonoma County Zoning Code (§ 11) Medium relevance
  • Sonoma County Zoning Code (section 2-76) Medium relevance
  • Sonoma County Zoning Code (§ V) Medium relevance
  • Sonoma County Zoning Code (§ II) Medium relevance
  • Sonoma County Zoning Code (§ IV) High relevance
  • Sonoma County Zoning Code (§ I) High relevance
  • Sonoma County Zoning Code (§ I) Medium relevance
  • Sonoma County Zoning Code (§ I) Medium relevance
  • Sonoma County Zoning Code (section to) Medium relevance
  • Sonoma County Zoning Code (title or) Medium relevance
  • Sonoma County Zoning Code (Article 70.) Medium relevance
  • Sonoma County Zoning Code (Section 26-88-015) Medium relevance
  • Sonoma County Zoning Code (Section 65858) High relevance
  • Sonoma County Zoning Code (article may) High relevance
  • Sonoma County Zoning Code (Section 26-54-010) Medium relevance
  • Sonoma County Zoning Code (article may) Medium relevance
  • Sonoma County Zoning Code (Article 94.) Medium relevance
  • Sonoma County Zoning Code (§ 4) Medium relevance
  • Sonoma County Zoning Code (§ II) Medium relevance
  • Sonoma County Zoning Code (§ VI) Medium relevance
  • Sonoma County Zoning Code (Section 26-92-040.) Medium relevance
  • Sonoma County Zoning Code (Section 26-28-160.) Medium relevance
  • Sonoma County Zoning Code (§ V) Medium relevance
  • Sonoma County Zoning Code (Article 56) Medium relevance
  • Sonoma County Zoning Code (Section 26-90-040) Medium relevance
  • Sonoma County Zoning Code (§ 13) Medium relevance
  • Sonoma County Zoning Code (Section 26-88-130) Medium relevance

Cited sections

Frequently asked questions

How do I find out which overlays apply to my unincorporated Sonoma County parcel?

Check the County’s official zoning database; it shows base zones and combining districts for each parcel (§ 26-02-130). Then open the cited article for each overlay (e.g., RC is Article 65) to see exact standards.

Do overlays change my setbacks or height limits?

Often yes. For example, the RC overlay imposes riparian setbacks of 100′/50′/25′ depending on corridor type (§ 26-65-040.H.2), and the BH overlay requires a 50′ wetland setback (§ 26-66-020.C). In scenic (SR) areas, design/siting rules can effectively shape building envelope (§ 26-64-020).

I’m in the floodplain. Can I still build?

In F2, new structures may be allowed if designed to meet County flood regulations (Chapter 7B) and other standards (§ 26-58-030). In F1 floodways, no new permanent/habitable structures are allowed (§ 26-56-020). Verify site specifics and “zero net fill” rules for the Laguna de Santa Rosa.

Are ADUs allowed in all areas?

Not everywhere. The Z overlay prohibits new ADUs (§ 26-76-010). Outside Z areas, ADUs are otherwise governed by County ADU provisions and state law; see local ADU rules and California ADU law.

Can overlays stop vacation rentals?

Yes. The X overlay can exclude new vacation rentals or cap them at 5% or 10% of single-family homes in the affected area (§§ 26-79-010, -020). Always confirm whether an exclusion or cap applies.

What if my site is in a scenic or historic overlay?

Expect design review. In SR, projects must be sited/screened per scenic criteria (§ 26-64-020, -050). In HD, exterior changes and demolition require County Landmarks review, and work must follow adopted district design guidelines (§§ 26-68-020, -025).

Do traffic-sensitive overlays reduce what I can build?

They can. In TS, intensity is capped by trip limits (e.g., 63 or 18 PM peak trips/acre) using ITE Trip Generation methods (§ 26-80-010). Projects must fit under the cap even if the base zone would otherwise allow more.

I have mature valley oaks—what should I know?

In VOH, removing a valley oak over 6″ DBH requires a zoning permit and mitigation; ≥36″ DBH removals require a use permit (§ 26-67-090). If your project needs design review, at least 50% of required landscape trees must be valley oaks (§ 26-67-100).

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