Overview
Code type
euclidean
Naming convention
conventional-suffix
| residential | R-1 (Low-Density), R-2 (Medium-Density), R-3 (Multi-Family) |
|---|---|
| commercial | CB (Central Business/Downtown), NC (Neighborhood Commercial), HC (Highway Commercial), OP (Office/Professional) |
| industrial | I-1 (Light Industrial), I-2 (Heavy Industrial) |
| overlays | HD (Historic District), FPO (Floodplain), AHO (Airport Hazard), RBP (Riparian Buffer Protection) |
Helena uses a conventional Euclidean scheme with separate base districts and layered overlays. Distinctive: post-October-2023 Montana state preemption package renders several dimensional standards and density caps legally unenforceable even while they remain in the Title 11 text. Height limits remain enforceable as they are not explicitly preempted by SB 245 or SB 382. Helena Planning Department (406-447-8444) provides written interpretation memos on which Title 11 provisions are still enforceable.
Districts
com 4res_sf 2ind 2res_mf 1
| Code | Name | Category | Min lot | Height | Coverage | FAR | Du/ac | Parking | Setbacks F/S/R |
|---|---|---|---|---|---|---|---|---|---|
| R-1 | Low-Density Residential | res_sf | 10,000 sf | 35 ft | 0.4 | 0.35 | 4.3 | 2 | 30 / 25 / 10 |
| R-2 | Medium-Density Residential | res_sf | 6,000 sf | 45 ft | 0.5 | 0.5 | 7.3 | 2 | 25 / 20 / 5 |
| R-3 | Multi-Family Residential | res_mf | 15,000 sf | 60 ft | 0.6 | 1.2 | 15 | 2 | 30 / 25 / 15 |
| CB | Central Business/Downtown | com | 5,000 sf | 60 ft | 0.85 | 2 | — | 2 | 10 / — / — |
| NC | Neighborhood Commercial | com | 5,000 sf | 45 ft | 0.7 | 1 | — | 2 | 15 / — / — |
| HC | Highway Commercial | com | 5,000 sf | 50 ft | 0.65 | 0.8 | — | 2 | 25 / — / — |
| OP | Office/Professional | com | 5,000 sf | 40 ft | 0.5 | 0.6 | — | 2 | 30 / — / — |
| I-1 | Light Industrial | ind | 20,000 sf | 50 ft | 0.5 | 0.5 | — | 2 | 25 / 25 / 10 |
| I-2 | Heavy Industrial | ind | 40,000 sf | 65 ft | 0.5 | 0.5 | — | 2 | 25 / 25 / 10 |
Confidence: confirmed partial under review not found
Overlays
HD
Historic District Overlay
HPFPO
Floodplain Overlay
FPAHO
Airport Hazard Overlay
APRBP
Riparian Buffer Protection Overlay
CORState preemptions
MT-SB-323-2023applies
Qualifying condition
Helena population (Census 2022 ACS estimate): 33,690. Threshold: >=5,000. 33,690 >= 5,000 = TRUE. Trigger also requires parcel.base_zone_category = res_sf. Helena has R-1 and R-2 single-family zones; predicate satisfies at parcel level for R-1/R-2 parcels.
Effect
Duplexes must be permitted as-of-right on any lot zoned single-family residential. Helena Title 11 R-1 and R-2 residential districts (§11-2-101) — single-family-only use lists are preempted; duplex must be added as by-right. Discretionary review for duplexes (CUP, variance, architectural review) is waived.
MT-SB-528-2023applies
Qualifying condition
Statewide ADU preemption applies regardless of city population. Trigger requires parcel.base_zone_category IN [res_sf, res_mf, res_th, mu]. Helena has R-1, R-2, R-3 residential zones; predicate satisfies.
Effect
At least one ADU must be permitted as-of-right on any residential lot. Helena Title 11 must allow ADUs by-right in R-1/R-2/R-3. Owner-occupancy requirements prohibited; additional parking requirements for ADU prohibited; no increased minimum lot size for ADU beyond what applies to primary dwelling.
MT-SB-382-2023applies
Qualifying condition
Helena population 33,690 >= 5,000 = TRUE. Trigger is population threshold.
Effect
Helena must adopt 10-year land-use plan with housing element under Montana Land Use Planning Act (MCA Title 76 Ch. 25). Once the adopted plan is in place, housing projects consistent with the plan receive ministerial (by-right) approval — no discretionary review, no public hearings for individual housing permits. Shifts entitlement from project-level to plan-level review. Helena Growth Policy 2023 update was an initial step; full MLUPA-compliant plan + regulatory framework integration is part of the in-progress Title 11 rewrite.
MT-HB-819-2023applies
Qualifying condition
Helena population 33,690 >= 5,000 = TRUE. Trigger also requires parcel.base_zone_category IN [res_sf, res_mf, res_th]. Helena has R-1 (min 10,000 sf), R-2 (min 6,000 sf), R-3 (min 15,000 sf) — all exceed the 2,500 sf cap.
Effect
Helena cannot impose minimum lot size greater than 2,500 sf for residential lots. R-1 10,000 sf, R-2 6,000 sf, R-3 15,000 sf minimums are legally unenforceable to the extent they exceed 2,500 sf. Effective minimum lot size for all Helena residential districts is 2,500 sf.
MT-HB-337-2023applies
Qualifying condition
Trigger requires parcel.base_zone_category = res_mf AND parcel.within_half_mile_transit = true. Helena has R-3 multi-family zone; transit proximity is parcel-level (resolved at site time via Helena Area Transit / Capital Transit route coverage — Helena operates fixed-route bus service with downtown-anchored radial coverage).
Effect
For multifamily projects on R-3 parcels within 1/2 mile of a transit stop, parking minimum is capped at 1.0 space per unit. Helena Title 11 §11-3-401 2-space-per-DU baseline for R-3 is preempted in transit-proximate R-3. Voluntary higher parking provision remains permissible; only the mandate is capped.
MT-SB-245-2023applies
Qualifying condition
Statewide preemption; trigger requires parcel.base_zone_category IN [res_sf, res_mf, res_th]. Helena has R-1/R-2/R-3. Predicate satisfies.
Effect
Local authority to cap dwelling units per acre in residential zones is removed. Helena R-1 (4.3 du/ac), R-2 (7.3 du/ac), R-3 (15 du/ac) density caps are legally unenforceable. Density governed instead by lot size (also HB 819-capped at 2,500 sf), setbacks, and building envelope.
MT-MCA-15-10-420-Property-Tax-Capapplies
Qualifying condition
Statewide property tax mill levy cap applies to all local governments including Helena.
Effect
State limits growth of local mill levies to one-half the average rate of inflation over the prior three years, plus newly taxable property. Does not alter zoning entitlements directly but constrains Helena's capacity to fund zoning infrastructure (planning staff, public works, utility extension) through property tax — indirectly affects entitlement throughput.
Adopted building codes
Local option to enforce
Click a code label to open its state-by-state adoption atlas.
Quirks & notes
Formulas
Definitions
- height
- Grade to highest point of structure. partial §Title 11 definitions
- lot_coverage
- Building footprint / lot area. partial §Title 11 definitions
- far
- Gross floor area / lot area. partial §Title 11 definitions
- du_ac
- Dwelling units per gross acre. NOTE: MT SB 245 (2023) preempts local du/ac caps in residential zones; local values retained for reference but not enforceable.
- setback_front
- Front property line to nearest building face. partial §Title 11 definitions
- setback_side
- Side property line to nearest building face. partial §Title 11 definitions
- setback_rear
- Rear property line to nearest building face. partial §Title 11 definitions
- parking
- Spaces per dwelling unit unless noted. NOTE: MT HB 337 (2023) caps MF parking at 1.0/unit within 1/2 mi transit.
Capacity calculations
- max_footprint_sf
lot_area_sf * lot_coverage- max_gfa_sf
lot_area_sf * far- buildable_width_ft
lot_width_ft - setback_side_ft * 2- buildable_depth_ft
lot_depth_ft - setback_front_ft - setback_rear_ft- max_stories_approx
max_height_ft / 10- max_units_post_preemption
lot_area_sf / max(min_lot_sf_after_HB819_cap, 2500) — SB 245 removes du/ac cap; building envelope + height are the binding constraints
Massing explorer
Interactive 3D comparison across every district. Drag to orbit, scroll to zoom, use the slider to walk districts, and toggle applicable overlays in the right-side panel.
Sort by
Max height
— ft
——
Floor area ratio
—
——
Lot coverage
—%
——
Setbacks (F / S / R)
— ft
——
Parking
— /unit
——
Max density
— du/ac
——
Min lot size
— sf
——
Copy zoning profile
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| District | Category | Height | FAR | Coverage | Setbacks | Parking | Density | Min lot | Overlays |
|---|
Research status
Publication gates
| primary url present | passed | code_source set to canonical Helena city-hosted code URL (ci.helena.mt.us). Helena code is not on Municode/amlegal/ecode360; primary is city-hosted. No mirror — Helena does not publish through a third-party codification vendor. |
|---|---|---|
| no aggregator cited | passed | Scanned all citations. Only primary sources: Helena City Code (Title 11), Montana Legislature (leg.mt.gov for SB 323/SB 528/SB 382/HB 819/HB 337/SB 245), MCA codification, FEMA NFIP (44 CFR §60.3), FAA Part 77 (14 CFR §77.9/77.19), Helena Regional Airport (HLN) Master Plan, USGS/EPA wetland classification, Montana DNRC riparian guidance, U.S. Census 2022 ACS. Zero references to Zoneomics, Steadily, SitePlanGuide, SitePlanCreator, Propwire, Zonara, or Unzoned. |
| confidence tags full form | passed | Every claim carries c§ section-tag OR explicit status (partial + partial_reason, inferred + derivation, not_found + search_performed, not_applicable + reason, preempted_by_state + preempting_law + preempted_value + preempted_effective_date, applies_fully, applies_at_parcel_level). v1's bare 'c'/'i' confidence shorthand fully replaced. |
| overlays have parameters trigger confidence | passed | All 4 local overlays (HD, FPO, AHO, RBP) carry ordinance_ref, geographic_trigger, parameters[] (multi-element), interaction_with_base, status, citation, and narrative_ref. All 7 state overlays (MT SB 323, SB 528, SB 382, HB 819, HB 337, SB 245, property tax cap) surface via state_preemptions_applicable[] with qualifying_condition_checked, effect, effective_date, preempted_fields_in_this_record, status, source_ref, narrative_ref. |
| preempt section city specific | passed | state_preemptions_applicable[] lists 7 entries tailored to Helena's specific status: population 33,690 (Census 2022) exceeds the 5,000 threshold for SB 323/SB 382/HB 819; SB 528/SB 245/property tax cap apply statewide; HB 337 applies at parcel level within 1/2 mi transit. Each entry carries Helena-specific qualifying_condition_checked computed from primary data (Census PEP), not a roster lookup. v1's generic reference to 'state-preemptions/montana.md' replaced with structured entries driven from state-overlays/montana.json. |
Data quality
64%completeness
Documented gaps
- Title 11 direct re-fetch (city-hosted platform not exercised this pass; Helena Planning Department 406-447-8444 authoritative)
- Comprehensive code rewrite adoption timeline (late 2026 / early 2027 per Helena Planning)
- HD Architectural Review Board scope over SB 382/SB 323/SB 528 by-right housing (unresolved in MT case law)
- Lot-coverage and FAR preemption status under SB 382 (contested)
- Parking-minimum preemption status under SB 382 (contested)
- Helena Growth Policy 2023 MLUPA-compliance status
- Helena Area Transit / Capital Transit route map for HB 337 1/2-mi transit proximity buffer computation
- CB/NC/HC/OP side and rear setback explicit values (v1 listed null; v2 confirms not_found pending re-fetch)
- Precise RBP buffer distances by stream size (75–150 ft range confirmed; specific values require local verification)
Known issues
freshness:volatiledata:gaps-present
Verification
| last_verified_at | 2026-04-19T08:35:00Z |
|---|---|
| verifier_specialist | verification-pass |
| verifier_version | 1.0 |
| verification_result | passed |
| atomic_claims_checked | 24 |
| atomic_claims_passed | 24 |
| atomic_claims_failed | 0 |
| notes | All confirmed claims carry c§ section-tag citations. Partial claims carry explicit partial_reason. Inferred values carry derivation. not_found values carry search_performed. No bare [confirmed] tags. No aggregator citations (Zoneomics, Steadily, SitePlanGuide, SitePlanCreator, Propwire, Zonara, Unzoned — absent). Montana 2023 preemption package citations point directly to leg.mt.gov bill PDFs and MCA codification. Population 33,690 (Census 2022 ACS) is primary-data source for SB 323/SB 382/HB 819 threshold check (not roster trust). |
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