Zoning, setbacks, and permitting for infill development in Boise. Covers ZOA25-000013 ADU rules and Idaho SB 1352 starter-home allowances effective July 1, 2026.
This guide summarizes Boise infill-development rules based on the City of Boise Zoning Code and Idaho Senate Bill 1352. Effective date: 2026-02-15 (ZOA25-000013) and 2026-07-01 (SB 1352). This is not legal advice. Standards change. Verify all information at https://codelibrary.amlegal.com/codes/boise_id/latest/boise/0-0-0-65305 and https://legislature.idaho.gov/sessioninfo/2026/legislation/s1352/ before making any development or acquisition decision.
Applicable code
Code references active as of publication. Verify current standards at the official source before any development decision.
Cities with populations over 10,000 must allow at least one accessory dwelling unit per lot in all residential zones. No owner-occupancy requirement may be imposed. No blanket square-footage bans permitted.
Investor implication: Boise must allow ADUs citywide regardless of local zoning preferences. Existing HOA restrictions remain enforceable, but HOAs cannot add new ADU bans without written consent of all members.
Verify at Idaho Legislature SB 1354 →Cities with populations over 10,000 must allow residential development at a minimum density of 12 units per acre on tracts of 4 acres or more. Lots as small as 1,400 square feet permitted. Setback and lot-width requirements do not apply to qualifying starter-home subdivisions.
Investor implication: Infill developers can pursue higher-density projects on larger parcels without local downzoning. Minimum lot size of 1,400 sq ft enables townhome and small-lot SFH products previously prohibited in many Boise zones.
Verify at Idaho Legislature SB 1352 →Residential zoning districts in Boise include R-1A (single-family, 7,500 sq ft min), R-1B (single-family, 6,000 sq ft min), R-1C (single-family, 5,000 sq ft min), R-2 (two-family, 5,000 sq ft min), R-3 (multi-family, 5,000 sq ft min per unit), and R-4 (multi-family, 2,500 sq ft min per unit). SB 1352 overrides these minimums for qualifying projects on tracts ≥4 acres.
Investor implication: Baseline zoning still applies to parcels under 4 acres and to projects not pursuing SB 1352 density. Investors must verify underlying zone before acquisition.
Verify at City of Boise Zoning Code →Properties within Boise's historic overlay districts (North End, Warm Springs, Fort Street) are subject to additional design review and demolition restrictions. New construction and exterior alterations require Historic Preservation Commission approval. HPC approval is discretionary and based on compatibility with the historic character of the district and compliance with adopted design guidelines.
Investor implication: Infill projects in historic overlays face longer approval timelines and stricter design standards. Demolition of contributing structures is rarely approved. Budget 6–12 additional months for design review. Approval is discretionary and can be denied based on design compatibility even if all zoning standards are met.
Verify at City of Boise Zoning Code →Off-street parking requirements vary by zoning district and use type. Accessory dwelling units located within one-half mile of a frequent transit route as designated by Valley Regional Transit are exempt from parking requirements. Multi-family projects typically require 1.5–2.0 spaces per unit depending on unit size and zone.
Investor implication: ADUs within ½ mile of frequent transit routes require no parking. ADUs outside this radius typically require 1 space per unit. Multi-family projects must provide 1.5–2.0 spaces per unit depending on zone and unit size. Verify transit proximity and zone-specific requirements before finalizing site plans.
Verify at City of Boise Zoning Code →Renew analysis
SB 1354 removes the most significant barrier to ADU development in Boise—local zoning prohibitions. Investors can now pursue ADU strategies in any residential zone, but must still verify HOA covenants on a per-parcel basis. Existing HOA bans are grandfathered; new bans require unanimous written consent, making them effectively unenforceable going forward.
SB 1352 is the most significant infill enabler in Idaho history. Boise's R-1C zone previously required 5,000 sq ft minimum lots; this is now overridden for qualifying projects. Developers can pursue 12+ units/acre on any 4+ acre residential parcel, regardless of underlying zoning. The 1,400 sq ft minimum lot size unlocks townhome and cottage-court products that were previously non-conforming in most Boise neighborhoods.
Boise's underlying zoning districts remain in effect for parcels under 4 acres and for developers not invoking SB 1352. R-1C (5,000 sq ft min) is the most common single-family zone in established neighborhoods. R-2 allows duplexes by right. R-3 and R-4 zones are concentrated near downtown and along arterials. Always verify the underlying zone via the City's zoning map before underwriting.
Historic overlays are the primary constraint on infill development in Boise's most desirable neighborhoods. North End and Warm Springs properties require HPC approval for any exterior change, including ADUs. Demolition of contributing structures is effectively prohibited. Investors pursuing infill in these areas must budget for architect-led design review and accept that some projects will be denied. Non-contributing structures face fewer restrictions but still require HPC approval.
This is the lowest-risk infill scenario in Boise. The Bench has minimal overlay restrictions, and single ADUs on conforming lots are now by-right under both state and local law. Underwrite conservatively on construction costs—detached ADUs typically run higher per-square-foot than attached conversions due to foundation and utility hookup costs.
Two-ADU strategies are now viable in Boise, but the 70% cap on combined ADU square footage is a binding constraint on smaller primary dwellings. Investors must run the math before acquisition—on a 1,800 sq ft primary, the maximum combined ADU square footage is 1,260 sq ft, not the nominal 900 + 500 = 1,400 sq ft. Underwrite conservatively and verify that the site can accommodate two structures within setback and height limits.
SB 1352 projects are the highest-upside infill opportunity in Boise, but they require significant capital and entitlement expertise. The 12 units/acre minimum is a floor, not a ceiling—developers can pursue higher densities if the site supports it. The 1,400 sq ft minimum lot size is a game-changer for townhome and cottage-court products. Budget 12–18 months for entitlement and expect public opposition in established neighborhoods. The law prohibits cities from denying projects on density grounds alone, but design, infrastructure, and compatibility standards still apply.