Hillsborough Zoning, Planning & Building Codes

Last reviewed: July 3, 2026

Overview

Hillsborough’s land-use rules are codified in Title 17 — ZONING, which establishes the town’s zoning map, purposes, and basic procedures. The ordinance’s stated purposes include implementing the general plan, protecting neighborhood scale, and conserving open space and light/air § 17.04.010 . The title is explicitly captioned the “Hillsborough Zoning Ordinance” and the town maintains an official zoning map on file with the city clerk § 17.04.020–030 . Key, frequently-used chapters include the definitions (Chapter 17.08), the zoning districts (Chapter 17.12), the uses table (Chapter 17.16), ADU/JADU rules (Chapter 17.52), two‑unit project rules (Chapter 17.54), variances (Chapter 17.40) and the town’s density bonus rules (Chapter 17.60) § 17.08.010; § 17.12.010; § 17.16.010; § 17.52.020; § 17.54.010; § 17.40.010; § 17.60.010 .

(For the town’s topical navigation pages, see Hillsborough Zoning and Hillsborough Land Use.)

How Hillsborough's code is organized

• Title-level structure: the zoning rules live in Title 17 and are arranged by subject chapters: General Provisions (Ch. 17.04), Definitions (Ch. 17.08), Zoning Districts (Ch. 17.12), Uses (Ch. 17.16), ADUs (Ch. 17.52), Two‑Unit Projects (Ch. 17.54), Variances (Ch. 17.40), Density Bonus (Ch. 17.60), etc. The title itself is named in the code § 17.04.020 and the purpose statement appears at § 17.04.010 .
• Official map: the town’s zoning map is adopted and kept on file with the city clerk § 17.04.030 .
• Cross-references: many procedural rules (design review, notice, hearings) refer to the planning/design chapter elsewhere in the code (for example the design review procedures in Chapter 2.12 are repeatedly referenced from Title 17) § 17.56.060; see also references in the ADU chapter .

Zoning district families

Hillsborough organizes its zoning into a small set of residential-focused district families; the zoning ordinance explicitly establishes three district types:

• Traditional residential (RD‑1) — intended mainly for single‑family development; the ordinance caps density at one dwelling per one‑half acre (exclusive of ADUs) § 17.12.010; § 17.16.010(A)(1) .
• Mixed residential (RD‑2) — created to accommodate townhomes and multifamily on specified town‑owned land; the chapter sets a minimum density of 20 units/acre where applied § 17.12.010; § 17.16.010(A)(2) .
• Governmental and residential mixed use (RD‑3) — allows town facilities plus limited residential units (the code notes a cap of 16 dwelling units on land zoned RD‑3) § 17.12.010; § 17.16.010(A)(3) .

The uses table and permitted/special‑permit markings for each district are located in Chapter 17.16 (Uses Permitted); the “P” (permitted) and “S” (special permit) conventions are applied there § 17.16.010 .

(For more on the town’s district map and permitted uses see Hillsborough Zoning and Hillsborough Land Use.)

Citywide development standards

Hillsborough distributes standards across Title 17 and associated chapters; below are the principal, town‑level rules and where to find them.

• Setbacks and measurement: the code uses dedicated setback and measurement chapter references (see the how distances are measured language and cross‑references to the setback chapter); for example some specialized setback rules reference Section 17.24.030 and other chapters for measurement procedures § 17.24.030 (measurement cross‑reference appears throughout Title 17) . See the town’s development standards page for the compiled objectives and tables.
• Height limits: general height limitations are organized under Chapter 17.28 (height limitations); many use‑ and project‑specific height rules defer to that chapter § 17.28 (see private‑school and other use standards referencing Chapter 17.28) .
• Floor‑area ratio (FAR) and lot coverage: ADU‑specific FAR and lot coverage rules are set in § 17.52.020.E.2–3, which (for ADUs) caps the combined floor area on the lot at 25% of net lot area for the first acre, plus 15% for area over one acre and also includes a structural coverage table (Table 17.52.020‑1) for maximum covered area by lot size § 17.52.020.E.2; § 17.52.020.E.3; Table 17.52.020‑1 .
• Parking: the town’s off‑street parking program and specialty rules live in Chapter 17.36 and related tables; the code explicitly bars the use of off‑street loading spaces to satisfy parking requirements § 17.36.270 . ADU parking requirements are spelled out in the ADU chapter: one off‑street space required per ADU, with specific exceptions (transit proximity, historic districts, ADU within primary residence, on‑street permit situations, car‑share, and concurrent permits) § 17.52.020.E.9 . (See Hillsborough Parking.)
• Typical numeric ADU standards you’ll find in the ADU chapter: maximum detached ADU height baseline 16 ft, with conditional increases to 18 ft (and limited exceptions to 20–22 ft in narrowly described situations); minimum 4 ft side/rear setbacks for most ADUs; maximum unit sizes of 800–1,000 sq ft depending on bedrooms and type, and ministerial approval when the ADU complies with the listed objective standards § 17.52.020.E.6–9; § 17.52.020.E.1 .
• Landscaping & screening: specific landscaping and screening rules (including water‑conservation requirements and when landscaping requires design review) are in Chapter 17.56 § 17.56.040–070 .

(For an at‑a‑glance table of numeric standards and measurement rules, see Hillsborough Development Standards.)

Design / discretionary review, variances & nonconforming rules

• Design review: objective projects and many building and landscape actions are routed through the town’s design‑review procedures (Chapter 2.12). Title 17 repeatedly ties project types (including ADU exceptions and landscaping) to Section 2.12.070 to determine whether a project is Type A (ministerial) or Type B (noticed/design review) and what approvals are required § 17.56.060; see also ADU exception rules referencing design review and Chapter 2.12 . (See Hillsborough Design Review.)
• Variances: the code authorizes variances where strict application of a requirement is impractical due to lot size, shape, topography, or other unique circumstances; variance applications, fees, public hearings before the city council, and required findings are in Chapter 17.40 § 17.40.010–020 . After a variance is granted, the applicant must apply for design review consistent with the variance § 17.40.020.E .
• Nonconforming uses and conditions: the Title defines “nonconforming zoning condition” and applies nonconforming rules in multiple places (for example ADU eligibility explicitly states that correcting certain nonconforming conditions is not required to approve an ADU) § 17.52.020.B; § 17.52.010 (definitions) . (For persistent nonconformance rules see the nonconforming uses chapter; see Hillsborough Nonconforming Uses.)

Specific plans & overlays

• The current Title 17 material provided defines the town’s zoning districts and discusses specialized overlay‑style controls (for example historic resource references in the ADU section and area‑specific ADU exceptions) but a named “specific plan” for a subarea is not present in the retrieved excerpts. ADU rules reference special treatment where a lot contains an “identified historical resource” and make ADUs in historic districts subject to exceptions § 17.52.020.E.11.e .
• The code points to overlay and resource protections in other chapters and ties overlay treatment into approvals and exceptions (see references to historic districts and the separate design review/exception process) § 17.52.020.E.11.e . (See Hillsborough Overlay Districts and Hillsborough Historic Preservation.)

If you need a consolidated map of overlay boundaries and specific‑plan text, verify with the town planning office or the zoning map on file (the code requires the zoning map be maintained by the city clerk) § 17.04.030 .

Building permits & the review/permit path

• Ministerial vs. discretionary: many routine approvals are ministerial when they meet the objective standards in the code. For example, an ADU that complies with all local ADU standards is approved ministerially; ADU exceptions that do not meet those standards require design review under Chapter 2.12 § 17.52.020; Chapter 2.12 .
• ADU permitting timeline & process: the ADU chapter requires an ADU planning permit for most ADU types (some small conversions may be building‑permit only), sets application/fee rules, and lists notice and recording (deed restriction) requirements tied to final occupancy § 17.52.020.C; § 17.52.020.F; § 17.52.020.E.13 .
• Two‑unit projects (state law implementation): the town’s Chapter 17.54 implements the state two‑unit law (Gov. Code § 65852.21) and structures a ministerial approval path for two‑unit projects with owner‑occupancy and notice/deed‑restriction requirements where applicable § 17.54.010–030 .
• Concurrent reviews / building code: Title 17 frequently cross‑references the local building and fire codes for technical compliance (for example ADUs must meet the building and fire code setbacks and sprinkler rules are addressed in the ADU chapter) § 17.52.020.C.1.a(3); § 17.52.020.C.2 . For state building‑standards reference see the California Building Standards Code (Title 24) and the ADU chapter’s incorporation of applicable building standards (the ADU chapter references compliance with state and local building standards) § 17.52.020 . (See California Building Standards Code.)

State housing law in Hillsborough

Hillsborough’s Title 17 integrates California housing law where state statutes preempt or require local implementation. Highlights:

• ADUs & JADUs: the town’s ADU chapter implements the state ADU framework (ministerial approvals, unit‑size baselines, setbacks, parking and impact‑fee limitations). The ADU chapter explicitly permits detached ADUs, converted ADUs, multifamily conversions, sets 4 ft minimum side/rear setbacks for most ADUs, and allows at least 800 sq ft units as a floor for objective standards § 17.52.020.E.1; § 17.52.020.E.7; § 17.52.020.E.1.c .
• Parking waivers & exceptions: the ADU chapter follows state limitations on parking requirements and lists multiple exceptions (e.g., within ½ mile of transit, historic districts, unit inside the primary dwelling, car‑share nearby) § 17.52.020.E.9 .
• Two‑unit laws and ministerial approvals: the town’s Chapter 17.54 implements Government Code § 65852.21 for two‑unit projects and establishes the ministerial review path and owner‑occupancy/deed‑restriction mechanics required for certain configurations § 17.54.010–030 .
• Density bonuses: the town’s density bonus chapter (Chapter 17.60) implements California Government Code § 65915–65917, giving applicants a defined path to request bonuses or concessions for qualifying affordable housing § 17.60.010–040 .

(For statewide statutory texts and how they change local procedures, consult California housing laws and California ADU law; Hillsborough’s ADU chapter repeatedly references the state framework in its approval and standards language.)

Practical orientation — turning code into a project step‑by‑step

1. Confirm zoning on the town’s official zoning map (Title 17 requires the map be kept on file) § 17.04.030 .
2. Read the district use table in Chapter 17.16 to confirm whether your use is P (permitted) or S (special permit) in the applicable district § 17.16.010 .
3. Check numeric development standards in the applicable chapters: setbacks (measurement cross‑references such as § 17.24.030), height (Chapter 17.28), lot coverage/FAR (see ADU table Table 17.52.020‑1 for ADU guidance) § 17.24.030; Chapter 17.28; Table 17.52.020‑1 .
4. Determine permit path: ministerial building permit (ADU meeting objective standards — § 17.52.020) versus ADU planning permit or discretionary review/variance (Ch. 2.12 and Ch. 17.40) § 17.52.020; § 17.40.010–020; Chapter 2.12 .
5. Expect neighborhood notice steps for ADUs and two‑unit projects as described in Title 17 (mailing/affidavit and deed‑restriction requirements) § 17.52.020.E.13; § 17.54.J .
6. Coordinate building permits and fire/sprinkler requirements with the permitting agency; ADU rules explicitly treat sprinklers and fire access as building/fire code matters § 17.52.020.C.2 .

Information gaps / what I could not confirm in the retrieved files

• The provided excerpts give the zoning district names and many chapter references, but the full district‑by‑district numeric tables for RD‑1 (setbacks, lot sizes, FAR, lot coverage outside ADU‑specific rules) are not present in the retrieved snippets — the exact RD‑1/RD‑2/RD‑3 baseline numeric standards (e.g., front‑yard depth for RD‑1, base FAR for RD‑2) were not located in the available extracts. Verify those district‑specific standards in the full Title 17 tables (look for chapters/tables that numerically list RD‑1 standards) or check the zoning map packet at the town clerk § 17.04.030 .
• Full text of Chapter 2.12 (design review) and of Chapter 17.28 (height table) was not included in the excerpts provided; the ADU and landscape sections reference those procedures and limits but the explicit design‑review rules and the town‑wide height table should be read in the full chapters (Chapter 2.12 and Chapter 17.28) for project submittal requirements and numeric heights. See the design‑review cross references § 2.12.070 and the height chapter references throughout Title 17 .

Source References

• Hillsborough Zoning Ordinance, Title 17 — General Provisions and Zoning Map (including § 17.04.010–030) .
• Hillsborough Municipal Code — Definitions, Zoning Districts, Uses (Ch. 17.08; Ch. 17.12; Ch. 17.16) § 17.08.010; § 17.12.010; § 17.16.010 .
• ADU/JADU rules — Chapter 17.52 (standards, FAR/coverage tables, parking, height, setbacks and ministerial/exception paths) § 17.52.020 (E.1–E.9, E.11–E.13) .
• Two‑unit projects — Chapter 17.54 (purpose, application and owner‑occupancy/notice/deed restrictions) § 17.54.010–030 .
• Variances — Chapter 17.40 (application, findings, public hearing) § 17.40.010–020 .
• Landscaping & design‑review cross references — Chapter 17.56 (landscape review triggers and design review requirement) § 17.56.040–070 .
• Density bonus implementation — Chapter 17.60 (integration with Gov. Code § 65915 et seq.) § 17.60.010–040 .
• Off‑street parking rules (example: loading stalls not allowed to count toward parking) — § 17.36.270 .