Local zoning · Hillsborough

Hillsborough — Zoning

Zoning under the Hillsborough local zoning and planning code, with the controlling citations.

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Last reviewed: July 2, 2026

Overview

Hillsborough’s zoning is codified in Title 17 - ZONING. The ordinance establishes a town zoning map, three residential districts, use rules, and objective development standards that control setbacks, lot coverage, height, and special programs such as ADUs and two‑unit projects. See the zoning map requirement at § 17.04.030 and the district list at § 17.12.010 for the legal starting points.

This page focuses only on what the Hillsborough zoning ordinance (Title 17) actually says about zoning (districts, permitted uses, and the key dimensional and procedural rules), with plain‑English interpretation and the most decision‑relevant citations.

Key rules and where to read them quickly

  • Zoning map and how parcel rules are determined: § 17.04.030.
  • Zoning districts established (names): § 17.12.010.
  • Permitted principal uses and district rules summary: § 17.16.010.
  • Development standards (setbacks, lot coverage, FAR, accessory structures): Chapter 17.24 and § 17.32.060.
  • Height envelope and maximums: Chapter 17.28 (esp. § 17.28.010).
  • Off‑street parking requirements: Chapter 17.36.
  • ADU standards and ministerial allowances: § 17.52.020 (ADU rules: size, setbacks, parking exceptions, FAR/coverage). See the town ADU rules here.
  • Two‑unit project (urban lot split / Gov Code compliance): Chapter 17.54.

Practical links you’ll want when applying: the town’s pages on development standards (/us/california/hillsborough/development-standards), parking (/us/california/hillsborough/parking), design review (/us/california/hillsborough/design-review), overlay districts (/us/california/hillsborough/overlay-districts), ADUs (/us/california/hillsborough/adu), and the California Building Standards Code (/us/california/building-codes). (Each of those topics is referenced in the ordinance as controlling or applicable to zoning decisions.)

District‑by‑district breakdown

Note: Hillsborough replaced older RD labels and now lists three districts by name in § 17.12.010. All quotations below are paraphrase/synthesis; consult the cited § for verbatim text.

RD‑1 — Traditional residential (RD‑1)

  • Purpose: Preserve single‑family character and neighborhood scale; implement general plan goals. § 17.12.010(1); general purposes at § 17.04.010.
  • Typical permitted uses: single‑family dwellings (principal permitted use); accessory structures and residential accessory uses consistent with Chapter 17.16 and the permitted uses table. See § 17.16.010(A)(1).
  • Key dimensional constraints that apply in practice:
    • Setbacks and measurement rules: front/street line and interior setbacks measured per § 17.24.020–030.
    • Lot coverage and limits (structural + hardscape) and softscape rules: § 17.32.060 (combined maximums and table of coverage by lot size).
    • Height / building envelope: maximum profile and inward slope rules in § 17.28.010.
  • Where it applies: essentially the Town’s single‑family neighborhoods identified on the zoning map; consult the official zoning map on file with the city clerk per § 17.04.030.

RD‑2 — Mixed residential (RD‑2)

  • Purpose: Allow townhomes and multifamily development on limited parcels, especially certain town‑owned land. § 17.12.010(2).
  • Typical permitted uses: multifamily and townhome uses; the ordinance sets a minimum density of 20 units/acre where RD‑2 applies (see § 17.16.010(A)(2)).
  • Key dimensional constraints: RD‑2 development is still subject to the same Chapters governing setbacks, height (Chapter 17.28), parking (Chapter 17.36), and development standards (Chapter 17.32), though project‑specific standards (including design review) will apply on a case‑by‑case basis. Verify site‑specific standards with the planning department; the ordinance ties RD‑2 to town‑owned parcels in practice.

RD‑3 — Governmental and Residential Mixed Use (RD‑3)

  • Purpose: Accommodate town facilities with limited residential uses on specific town‑owned land. § 17.12.010(3).
  • Typical permitted uses: town/government facilities with limited residential units; the code caps residential capacity (example: maximum of 16 dwelling units on RD‑3 parcels where the district is used). See § 17.16.010(A)(3).
  • Key dimensional constraints and process: subject to the same Chapters for height, coverage, parking and design review; municipal projects often require tailored approvals and council review. Verify applicability on the zoning map and with planning staff.

Quick standards and permitted‑use table (decision‑relevant)

Topic / District Key rule (plain English) Code reference
Districts established (names) RD‑1 (Traditional residential), RD‑2 (Mixed residential), RD‑3 (Governmental & residential mixed use) § 17.12.010
RD‑1 density/use Single‑family dwellings; max typically one dwelling per 0.5 acre (see text) § 17.16.010(A)(1)
RD‑2 density Minimum 20 units/acre where RD‑2 applies (town‑owned sites) § 17.16.010(A)(2)
RD‑3 cap Town facilities with limited residential — max 16 units on RD‑3 land § 17.16.010(A)(3)
Lot coverage (residential) Structural + hardscape ≤ 50% of net lot area (with street setback exceptions); detailed table by lot size in code § 17.32.060
Height envelope Building envelope: 22 ft at setback line then 45° internal slope to max 32 ft measured from warped plane; see diagrams § 17.28.010
ADU standards Min 4' side/rear setbacks; 25' front setback; size limits, FAR/coverage limits and parking exceptions — ministerial approval if standards met § 17.52.020
Zoning map Official map determines district; copy kept with city clerk § 17.04.030
Parking rules Residential parking minimums, garage sizing, backup space and exceptions for ADUs Chapter 17.36 (see § 17.36.010–030)
Two‑unit projects Town permits two‑unit projects under limits (unit sizes, heights, setbacks, parking); special findings for denial allowed for specific adverse impacts Chapter 17.54 (esp. § 17.54.010–030)

Practical guidance and synthesis (plain English, applied)

  • Confirm the parcel’s legal zoning on the official zoning map first; the map controls which district’s rules apply to a lot (§ 17.04.030). If the map is ambiguous or the parcel is split between zones, ask planning staff — Verify with the jurisdiction.
  • For most homeowners in RD‑1, the ordinance preserves single‑family character: standard setbacks, building envelope rules, and strict lot‑coverage math (see § 17.24, § 17.28, § 17.32.060) will limit footprint and height. If you’re planning an addition, check Chapter 17.32 for coverage and Chapter 17.28 for the building envelope.
  • If you want to add an ADU, Hillsborough’s ADU rules are in § 17.52.020 and allow ministerial approvals when objective standards are met; note the 4‑ft side/rear setback minimum, 25‑ft front setback, and parking rules and exceptions. Also see the town ADU page for the application path.
    • ADU size limits, FAR and lot coverage formulas are numeric and specific (see Table 17.52.020‑1 and the FAR formula) — run the arithmetic on your lot early.
  • If your project exceeds ordinary limits (variance, design review threshold, or very large houses), expect design review and possible City Council involvement (see § 17.32.040 and references to the architecture and design review board). For very large homes (>8,000 sq ft) the code requires Council review after the design board stage (§ 17.32.040).
  • Parking and garage geometry are controlled in Chapter 17.36; ADUs have specific parking exceptions in § 17.52.020(E)(9) if near transit or in historic districts. Link to the town parking guidance and check for on‑street permit conditions before assuming exemptions.

Checklist

  • Confirm parcel zoning on the official zoning map and note district: § 17.04.030.
  • Verify permitted uses for that district: § 17.16.010 (RD‑1 / RD‑2 / RD‑3).
  • Calculate lot coverage (structural + hardscape), open space and FAR limits per § 17.32.060 and Table 17.52.020‑1 if planning ADU.
  • Check building envelope and height rules: § 17.28.010.
  • Confirm setback measurements per § 17.24.020–030; ADU setbacks per § 17.52.020(E)(7).
  • Count required parking and note ADU parking exceptions: Chapter 17.36 and § 17.52.020(E)(9).
  • Determine whether design review or architecture/design board review applies; consult § 17.32.040 and the design review chapter referenced in the code.
  • If seeking relief (variance) note the standards and lapse rules in Chapter 17.40.
  • For two‑unit projects (Urban Lot Split/second unit rules) consult Chapter 17.54 for unit size, height and setback special rules.

Risks & Ambiguities

Issue Why it matters What to verify
Parcel‑level district boundary A single parcel could be split or mis‑mapped; district determines all rules Confirm official zoning map with city clerk; cite § 17.04.030.
Exact permitted uses/details The ordinance provides a permitted‑uses table but not every niche use is spelled out in summary Inspect the full § 17.16.010 uses table and request planning clarification for marginal uses.
Development standards interplay (FAR vs coverage vs ADU limits) Multiple numeric limits can interact and further reduce allowable building area Run coverage/FAR math against § 17.32.060 and § 17.52.020 Table(s) early; when within a few hundred sq ft, recordation notices may be required.
Applicability of RD‑2 minimum density RD‑2 applies only to certain parcels (town‑owned in text) — a developer might assume wider applicability Verify whether the specific parcel is zoned RD‑2 on the map and whether minimum density is required; see § 17.12.010 and § 17.16.010(A)(2).
Design review triggers Some projects (e.g., >8,000 sq ft, or ADU exceptions) require design review or council review Check § 17.32.040 and the ADU exception language in § 17.52.020; plan on public hearing if thresholds met.
Overlay districts and special historic rules The ordinance references "architecturally and historically significant historic districts" for ADU/parking exceptions, but specific overlay names/maps may not be in retrieved text Not found in retrieved materials — request the town’s overlay district map and specific overlay code sections. Verify with the jurisdiction.

Plain‑English summary

Hillsborough’s zoning (Title 17) is narrowly residential: three named districts (RD‑1, RD‑2, RD‑3) control where single‑family homes, multifamily/townhomes (in limited places) and town facilities may be built; the ordinance sets objective rules for setbacks, coverage, height, parking, and ADUs — check the zoning map to see which district applies to your lot and then apply the numeric rules in Chapters 17.24, 17.28, 17.32, 17.36, and § 17.52.020 for ADUs.

Source References

  • Hillsborough Zoning Ordinance, Title 17 — General provisions and zoning map: § 17.04.010–030.
  • Hillsborough zoning districts: § 17.12.010 (RD‑1, RD‑2, RD‑3).
  • Uses permitted in districts: § 17.16.010.
  • ADU rules (setbacks, size, FAR, parking exceptions): § 17.52.020 (Table 17.52.020‑1).
  • Lot coverage and coverage table: § 17.32.060 and Table for structural coverage.
  • Building envelope / height limitations: § 17.28.010.
  • Off‑street parking: Chapter 17.36 (see § 17.36.010–030).
  • Two‑unit projects: Chapter 17.54 (requirements and constraints).
  • Design review thresholds and Council review for very large homes: § 17.32.040.
  • Hillsborough Development Standards page: /us/california/hillsborough/development-standards
  • Hillsborough Parking page: /us/california/hillsborough/parking
  • Hillsborough Design Review page: /us/california/hillsborough/design-review
  • Hillsborough Overlay Districts page: /us/california/hillsborough/overlay-districts
  • Hillsborough ADU page: /us/california/hillsborough/adu
  • California Building Standards Code (Title 24) reference page: /us/california/building-codes

Sources

Retrieved passages

  • CBC § 3 (§ 3) High relevance
  • Hillsborough Zoning Code (Title 17) High relevance
  • Hillsborough Zoning Code (Section 21155) High relevance
  • Hillsborough Zoning Code (title shall) High relevance
  • Hillsborough Zoning Code (Section 17.32.020) Medium relevance
  • Hillsborough Zoning Code (Section 17.24.030) Medium relevance
  • CBC § 66321 (§ 66321) Medium relevance
  • Hillsborough Zoning Code (Chapter 17.56) Medium relevance
  • Hillsborough Zoning Code (chapter must) High relevance
  • Hillsborough Zoning Code (chapter of) High relevance
  • Hillsborough Zoning Code (section is) High relevance
  • California Fire Code High relevance
  • Hillsborough Zoning Code Medium relevance
  • Hillsborough Zoning Code (Section 21155) Medium relevance

Cited sections

Frequently asked questions

What are Hillsborough’s zoning districts?

Hillsborough’s ordinance establishes three districts: RD‑1 (Traditional residential), RD‑2 (Mixed residential), and RD‑3 (Governmental & residential mixed use). See the authority for the districts at § 17.12.010 which lists the district names.

What can I build on an RD‑1 lot in Hillsborough?

An RD‑1 lot is intended for single‑family dwellings and accessory residential uses; you must meet the town’s setbacks, lot‑coverage and height rules in Chapters 17.24, 17.28 and 17.32. Refer to § 17.16.010(A)(1) and the development standards cited in Chapter 17.32.

What are Hillsborough’s setback requirements?

Setback measurement rules are in § 17.24.020–030; ADUs have specific minimum setbacks (4 ft side/rear, 25 ft front for the ADU standards) in § 17.52.020(E)(7). Always measure per the code’s measurement rules in § 17.24.030.

Do I need design review for a large new house in Hillsborough?

If a proposed primary dwelling exceeds 8,000 square feet, the design record must go to City Council after Architecture and Design Review Board action per § 17.32.040; other projects may also trigger design review under the town’s design review procedures. Check § 17.32.040 for the Council review requirement.

What does the zoning map control and where is it kept?

The official zoning map delineates district boundaries and controls which Title 17 rules apply to a parcel; a copy of the zoning map is kept on file with the city clerk per § 17.04.030. Always confirm a parcel’s designation using that official map.

Can I add an ADU in Hillsborough and what are the main limits?

Yes—ADUs are permitted subject to § 17.52.020: minimum 4‑ft side/rear setbacks, 25‑ft front setback (with state constraints), specific size limits (800–1,000+ sq ft depending on bedrooms and whether the ADU is attached), FAR/coverage caps and parking rules (including exceptions). ADUs that meet objective standards are ministerially approved; noncompliant ADUs may be allowed through the ADU exception/design‑review path.

What parking requirements apply to new houses or ADUs?

Residential parking geometry and minimums are in Chapter 17.36 (e.g., garage and backup space sizes). ADUs require one off‑street space unless an exception applies (transit proximity, historic district, part of primary residence conversion, etc.) — see § 17.52.020(E)(9) for ADU parking exceptions.

When will the town deny a two‑unit project under Hillsborough rules?

Chapter 17.54 allows two‑unit projects but authorizes denial if the building official finds a specific, adverse impact on public health or the physical environment that cannot be mitigated. The standard and denial process are in Chapter 17.54.

Are there overlay or historic district exceptions I need to know about?

The code references “architecturally and historically significant historic districts” (for example, as an ADU parking exception) in § 17.52.020(E)(9)(2), but specific overlay names/maps were not fully present in the retrieved text — request the overlay district map and chapters from the town for parcel‑specific confirmation.

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