Local zoning · St. Helena
St. Helena — Overlay Districts
Overlay Districts under the St. Helena local zoning and planning code, with the controlling citations.
Last reviewed: July 6, 2026
Overview
St. Helena’s zoning code (Title 17) adds “overlay” districts on top of base zoning to address flood risk, downtown parking constraints, historic resources, mobile home parks, and master-planned projects. Overlay rules apply in addition to base zoning, and when there’s a conflict the overlay controls. The city recognizes five overlays in Chapter 17.21: the Flood Plain (FP), Mobile Home Park (MHP), Parking Exemption District (PED), Historic Preservation (HP), and Planned Development (PD) overlays (see Table 17.21(A)). § 17.21.005
In St. Helena, an overlay district adds special regulations on top of the base zoning for a mapped area, and if the two ever conflict, the overlay’s rule wins. § 17.21.005
Use this page together with the broader zoning, land use, development standards, parking, and design review guides to see how overlays interact with citywide rules.
District-by-district breakdown
Flood Plain Overlay (FP)
- Purpose and where it applies
- Identifies areas within the FEMA 100‑year floodplain and imposes additional protections. Applicability is based on FEMA maps and the General Plan Safety Element kept on file with Community Development. § 17.21.010(A)-(B)
- Typical permitted and prohibited uses
- Uses otherwise allowed by the base district may proceed unless specifically prohibited; the overlay prohibits critical and emergency facilities like hospitals, health care facilities, emergency shelters, fire stations, and telecommunication facilities. § 17.21.010(C)
- Key dimensional and development standards
- Waterway setbacks measured from the “top of bank”: 50 ft at the Napa River and 20 ft at Sulphur Springs Creek. § 17.21.010(E)
- Building height is measured from the mapped flood elevation rather than natural grade within the overlay. § 17.21.010(G)(4)
- Riparian construction fencing is required at the edge of the setback during construction. § 17.21.010(F)(2) (Riparian Area Protection)
- Subdivisions/new development must be reviewed by the City Engineer to minimize flood damage and ensure utility placement and drainage address flood hazards. § 17.21.010(H)
- New construction/replacement is also subject to the city’s flood-damage prevention standards in a separate title (cross‑referenced in § 17.21.010(D)); confirm details with staff to stay in zoning scope. § 17.21.010(D)
- Notes
- Open space parcels along Sulphur Springs Creek must meet both base OS standards and FP overlay setbacks. § 17.20.040(C)
Mobile Home Park Overlay (MHP)
- Purpose and where it applies
- Enables establishment/operation of mobile home parks when combined with a residential base zone; applied via a zoning map amendment for specific sites. § 17.21.020(A)-(B)(1)
- Process and required approvals
- Requires a simultaneous zoning map amendment (to add MHP) and a Conditional Use Permit (CUP) for the park; both are considered together. § 17.21.020(B)(1)
- Submittal must include a detailed site sketch and technical data (e.g., topography, trees to be removed, inundation areas, easements, mobile‑home space dimensions, and utility lines). § 17.21.020(B)(2)
- Typical permitted uses
- Installation of mobile homes that meet applicable federal/state regs; accessory structures per state rules (CCR Title 25). § 17.21.020(C)
- Key development standards
- Screening on street setback lines and along all other property lines; landscaped setbacks with irrigation; vehicle parking and access per Chapter 17.26; mobile homes must be on a permanent foundation. § 17.21.020(E)
- Enforcement and other notes
- State HCD enforces the Mobilehome Parks Act; the city notes parks in flood hazard areas must also comply with the city’s flood rules (separate title). § 17.21.020(F)
- In the base residential districts, “mobile home” is a CUP‑level use; the overlay adds the park framework. See Table 17.16.020(A). § 17.16.020 (table note to § 17.21.020)
- For landscaping specifics, also see landscaping and screening.
Parking Exemption District (PED)
- Purpose and where it applies
- Covers an area, generally within the CB (Central Business) district, where on‑site parking requirements (and any in‑lieu fee) do not apply, in order to preserve the historic downtown building pattern. § 17.21.030(A)
- Typical permitted uses
- Uses follow the base zoning; the overlay only modifies parking obligations. Projects in the PED are “not subject to on-site parking requirements.” § 17.26.060(A) and § 17.21.030(A)
- Key standards
- Maintain any existing on‑site parking. § 17.21.030(B)
- Short‑term bicycle parking requirements do not apply to uses located within the PED (as a listed exemption). § 17.26.080(A)(1)(d)(i)
- The city may update PED standards after a downtown parking study; verify status with staff. § 17.21.030 n.1
Historic Preservation Overlay (HP)
- Purpose and where it applies
- Safeguards the city’s historic and architectural character; applies to parcels on the HP overlay map, including properties on the city’s historic resources list, designated local districts, and other designated resources. § 17.21.040(A)-(B)
- Review and approvals
- All infill development in the HP overlay requires design review by the Planning Commission. § 17.21.040(C)
- Rehabilitation work inconsistent with HP standards requires Major Design Review; new construction/additions visible from the public right‑of‑way or increasing floor area by more than 25% of the primary structure also require Major Design Review. § 17.21.040(E)-(F) (triggers summarized)
- Core standards (preservation and infill)
- Applies the Secretary of the Interior’s Standards (mandatory for listed buildings) and city compatibility criteria—e.g., maintain unifying patterns such as setbacks, coverage, height, transparency, eave depth, and street orientation. § 17.21.040(E)-(F)(2)
- For infill on residential blocks, front setbacks must match the average of nearby houses (two methods allowed). § 17.21.040(F)(2)(a)(ii)
- Accessory structures visible from the street must echo the main structure but be clearly subordinate. § 17.21.040(F)(2)(e)
- Owners may opt to use the California Historic Building Code for designated historic resources; coordinate early with staff and the building official. § 17.21.040(G)
- Related guidance
- For city processes, see design review and historic preservation. Signs in historic areas should also align with signage rules where applicable.
Planned Development Overlay (PD)
- Purpose and where it applies
- Provides a flexible, master‑planned approach to implement General Plan goals with single- or mixed‑use projects that deliver superior design, environmental preservation, housing variety, and amenities. § 17.21.050(A)
- Typical permitted uses
- May include any use(s) permitted in other districts so long as they’re compatible and consistent with the General Plan. § 17.21.050(B)(2)
- Key dimensional and development standards
- PD standards (lot sizes, density/FAR, setbacks, heights, signs, parking, landscaping/screening) are set within the PD approval and prevail over the base zoning; where the PD is silent, base standards apply. § 17.21.050(B)(3), (B)(6)
- Minimum PD area is 1 acre, with flexibility to go smaller if certain suitability findings are made (e.g., topography, historic character, isolated problem area). § 17.21.050(B)(1)
- Park/open‑space dedication and dedication of streets/bike/ped ways to the city may be required. § 17.21.050(B)(4)-(5)
- Process and approvals
- Initiation: City Council, Planning Commission, Community Development Director, or property owner/agent. § 17.21.050(C)
- Processed as a zoning map amendment with a development plan/policy statement; Major Design Review is required before building permits. § 17.21.050(F)
- Application materials include a site features map, infrastructure phasing, inclusionary housing compliance (for residential), detailed district regulations (min. lot size/width, max. density/FAR, setbacks, heights, coverage, accessory rules, parking, design guidelines) and development plan elements (circulation, grading/drainage, open space, building sketches, phasing). § 17.21.050(D)-(E)
- Required findings include superiority to base zoning outcomes and adequate services/transportation. § 17.21.050(G)
- Lapse/extension: If no Design Review approvals are obtained and construction hasn’t started within 2 years, the city may remove the PD designation; extensions are possible under § 17.04.140. § 17.21.050(I)
- Notes
- Departures allowed in one PD don’t set precedent for others. § 17.21.050(B)(7)
- For variance‑type relief outside a PD, see variances and exceptions.
Key overlay standards at a glance
| Overlay | Most decision-relevant standard | Where it applies | Code Reference |
|---|---|---|---|
| FP | Setbacks from top of bank: Napa River 50 ft; Sulphur Springs Creek 20 ft; critical facilities prohibited; height measured from flood elevation | FEMA 100‑yr floodplain per city files | § 17.21.010 |
| MHP | Must rezone to add MHP and obtain a CUP; park must have perimeter screening and irrigated landscaped setbacks; parking per Ch. 17.26 | Only where City Council applies MHP to a residential site | § 17.21.020 |
| PED | No on‑site parking required; existing onsite spaces must be maintained; bike parking not required for uses in PED | Generally within downtown CB | § 17.21.030; § 17.26.060; § 17.26.080 |
| HP | Infill requires Planning Commission design review; use Secretary of Interior’s Standards; front setback averaging for infill | Parcels on HP map and local historic resources | § 17.21.040(C),(E)-(F) |
| PD | PD standards override base zoning; min. 1 acre (with exceptions); processed as zoning map amendment; Major Design Review before permits; 2‑year lapse if idle | Sites approved by City Council for PD | § 17.21.050(B),(F),(I) |
Practical guidance
- Start by confirming whether your parcel has an overlay in the city’s official maps; then apply the overlay rule set in addition to your base zone. § 17.21.005
- In the FP overlay, design early around waterway setbacks and the special height datum; integrate these with your base district’s development standards. § 17.21.010
- In the PED, plan for zero on‑site parking unless you already have spaces (which must be kept). Coordinate any shared/reduced parking ideas with the city’s parking rules. § 17.21.030; § 17.26.060
- In the HP overlay, assume a design‑review step and align with city and federal preservation standards; explore the California Historic Building Code option with staff, noting it sits within the separate California Building Standards Code. § 17.21.040(C),(E)-(G)
- For MHP and PD, expect a zoning map amendment and robust submittals; early pre‑application meetings with Community Development reduce rework. § 17.21.020(B); § 17.21.050(C)-(F)
Checklist
- Confirm base zone and any overlay designation on your parcel (HP, FP, PED, MHP, PD). § 17.21.005
- If in FP, map your top‑of‑bank setbacks and verify the flood elevation used for height measurement. § 17.21.010(E), (G)(4)
- If in PED, validate boundary and whether any existing onsite spaces must be retained; confirm any shared/demand‑based strategies with staff. § 17.21.030(B); § 17.26.060(A)
- If in HP, plan for Planning Commission design review and design to HP compatibility standards; check whether your project triggers Major Design Review. § 17.21.040(C),(F)
- For MHP, prepare rezoning + CUP applications and the required technical exhibits; coordinate screening/landscaping and parking plans. § 17.21.020(B)-(E)
- For PD, assemble the policy statement and development plan with full standards; expect Major Design Review before permits. § 17.21.050(D)-(F)
- If a rule seems to conflict with a base standard, apply the overlay; if relief is needed, discuss options under variances and exceptions. § 17.21.005
Risks & Ambiguities
| Issue | Why it matters | What to verify |
|---|---|---|
| Floodplain boundaries shift | FEMA updates can move the FP overlay line, changing setbacks and height datum | Confirm current FP maps and flood elevation used for § 17.21.010 compliance |
| Downtown PED coverage | The PED is “generally within the CB” and may be updated after a parking study | Confirm parcel’s PED status and whether post‑study standards apply (§ 17.21.030 n.1) |
| HP design review triggers | Some projects must go to Planning Commission; missing this can delay permits | Whether your scope triggers Major Design Review under § 17.21.040(F) |
| MHP state vs. city rules | HCD enforces the Mobilehome Parks Act; the city still applies local zoning/landscape/parking | Confirm submittals and city expectations under § 17.21.020(E)-(F) |
| PD lapse | PD approvals can be removed if inactive after 2 years | Timeline and extension options under § 17.21.050(I) |
| Overlay vs. base standards | Overlays prevail where conflicts arise | Which specific overlay provision supersedes the base (§ 17.21.005) |
Plain-English Summary
Overlays are custom rule layers that sit on top of your base zoning. If you’re near the river or creek, the FP overlay adds setbacks and a flood‑elevation height datum; downtown storefronts in the PED don’t have to provide on‑site parking; homes in the HP overlay need compatible design and Commission review; MHP and PD overlays are site‑specific re-zonings that set up mobile‑home parks or master‑planned projects with their own standards. § 17.21.010; § 17.21.030; § 17.21.040; § 17.21.020; § 17.21.050
Source References
- § 17.21.005 Districts designated (overlay list and overlay/base relationship)
- § 17.21.010 Flood Plain Overlay (FP) (purpose, applicability, prohibited uses, setbacks, height datum, riparian fencing, subdivision review)
- § 17.21.020 Mobile Home Park Overlay (MHP) (rezoning + CUP, uses, standards, enforcement)
- § 17.21.030 Parking Exemption District (PED) (purpose, standards) and related § 17.26.060, § 17.26.080
- § 17.21.040 Historic Preservation Overlay (HP) (purpose, applicability, reviews, preservation/infill standards, CHBC option)
- § 17.21.050 Planned Development Overlay (PD) (purpose, area, uses, standards, applications, findings, lapse)
- Related cross-references: § 17.16.020 (mobile home CUP table note to MHP); § 17.20.040(C) (OS and FP overlay); St. Helena zoning overview
Sources
Retrieved passages
- St. Helena Zoning Code (Title 17) High relevance
- St. Helena Zoning Code (Title 17) High relevance
- St. Helena Zoning Code (Title 17) High relevance
- CBC § 5 (§ 5) High relevance
- St. Helena Zoning Code (Title 17) High relevance
- St. Helena Zoning Code (Title 17) High relevance
- St. Helena Zoning Code (Chapter 17.21) High relevance
- St. Helena Zoning Code (Title 17) High relevance
- St. Helena Zoning Code (§ 5) High relevance
- St. Helena Zoning Code (Title 17) High relevance
Cited sections
- § 17.21.005 Districts designated (overlay list and overlay/base relationship) (§ 17.21.005)
- § 17.21.010 Flood Plain Overlay (FP) (purpose, applicability, prohibited uses, setbacks, height datum, riparian fencing, subdivision review) (§ 17.21.010)
- § 17.21.020 Mobile Home Park Overlay (MHP) (rezoning + CUP, uses, standards, enforcement) (§ 17.21.020)
- § 17.21.030 Parking Exemption District (PED) (purpose, standards) and related § 17.26.060, § 17.26.080 (§ 17.21.030)
- § 17.21.040 Historic Preservation Overlay (HP) (purpose, applicability, reviews, preservation/infill standards, CHBC option) (§ 17.21.040)
- § 17.21.050 Planned Development Overlay (PD) (purpose, area, uses, standards, applications, findings, lapse) (§ 17.21.050)
- Related cross-references: § 17.16.020 (mobile home CUP table note to MHP); § 17.20.040(C) (OS and FP overlay); St. Helena zoning overview (§ 17.16.020)
- StHelena_ZoningCode.md
Frequently asked questions
Does an overlay replace my base zoning in St. Helena?
No. Overlays add rules on top of the base zoning. If a base standard conflicts with an overlay, the overlay controls, but the underlying use and development permissions in your base zone still apply otherwise. § 17.21.005
What are the creek and river setbacks in the Flood Plain Overlay?
From the top of the bank, the overlay requires a 50 ft setback at the Napa River and a 20 ft setback at Sulphur Springs Creek. These apply in addition to any base‑district setbacks. § 17.21.010(E)
How is building height measured in the floodplain?
Within the Flood Plain Overlay, building height is measured from the flood elevation—not from natural grade—so your project’s height envelope effectively “floats” with the mapped elevation. § 17.21.010(G)(4)
Is my downtown project exempt from providing parking?
If your site is within the Parking Exemption District, projects are not subject to on-site parking requirements, though any existing on‑site spaces must be maintained. Confirm the PED boundary with staff. § 17.26.060(A); § 17.21.030(B)
What triggers design review in the Historic Preservation Overlay?
All infill development in the HP overlay requires Planning Commission design review. New construction or visible additions over 25% of the primary structure also require Major Design Review. § 17.21.040(C), (F)
Can I use modern architecture in the HP overlay?
Yes, if it’s compatible. The HP standards require maintaining unifying patterns (setbacks, height, coverage, etc.) and using the Secretary of the Interior’s Standards for listed buildings; front‑setback averaging is specifically required for infill on residential blocks. § 17.21.040(E)-(F)
How do I establish a mobile home park?
You must apply for a zoning map amendment to add the MHP overlay and a CUP for the park at the same time, with detailed site and technical exhibits. State HCD enforces park operations; the city applies local zoning, landscaping, and parking standards. § 17.21.020(B)-(F)
What is a PD overlay and why use it?
A PD overlay lets the city approve a master plan with custom standards that can mix uses and deviate from base rules, provided findings show a demonstrably superior project. It’s processed as a zoning map amendment and requires Major Design Review before building permits. § 17.21.050(B), (F), (G)
Do PD approvals expire?
They can. If Design Review approvals aren’t obtained and construction hasn’t begun within two years, the city may remove the PD designation unless an extension is granted. § 17.21.050(I)
Are bicycle parking spaces required downtown?
Short‑term bicycle parking is not required for uses located within the Parking Exemption District (and some other limited exemptions), but confirm whether your site is actually inside the PED. § 17.26.080(A)(1)(d)(i)
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