Boise Zoning Guide

R-1A (Estate Residential): Minimum lot size 10,000 sq ft, maximum density 4.35 units/acre, minimum lot width 75 feet, front setback 20 feet, side setback 10 feet (corner 15 feet), rear setback 25 feet.

Investor implication: R-1A is the lowest-density residential zone. Acquisition targets are typically large-lot teardowns in established neighborhoods (North End, East End) where lot value exceeds improvement value. Infill development is constrained by dimensional requirements.

R-1B (Low-Density Residential): Minimum lot size 7,000 sq ft, maximum density 6.22 units/acre, minimum lot width 60 feet, front setback 20 feet, side setback 5 feet (corner 15 feet), rear setback 20 feet.

Investor implication: R-1B is the most common single-family zone in Boise. Lot dimensions support standard production builds and minor land divisions. Primary target for flip acquisitions and SFH rental portfolios.

R-1C (Medium-Density Residential): Minimum lot size 5,000 sq ft, maximum density 8.71 units/acre, minimum lot width 50 feet, front setback 15 feet, side setback 5 feet (corner 10 feet), rear setback 15 feet.

Investor implication: R-1C allows tighter lot configurations. Common in newer subdivisions and infill parcels. Supports duplex development on conforming lots and ADU strategies.

R-2 (Medium-High Density Residential): Minimum lot size 3,500 sq ft per unit, maximum density 12.45 units/acre, minimum lot width 40 feet, front setback 15 feet, side setback 5 feet (corner 10 feet), rear setback 15 feet. Permits single-family, duplex, triplex, fourplex, townhomes, and accessory dwelling units.

Investor implication: R-2 is the primary missing-middle zone. Permits up to fourplex by right. Target for small multifamily infill and townhome projects. Lot assembly strategies unlock higher unit counts.

R-3 (High-Density Residential): Minimum lot size 2,500 sq ft per unit, maximum density 17.42 units/acre, minimum lot width 40 feet, front setback 15 feet, side setback 5 feet (corner 10 feet), rear setback 15 feet. Permits all residential building types including apartments and condominiums.

Investor implication: R-3 supports garden-style multifamily and mid-rise residential. Concentrated near transit corridors and downtown. Acquisition targets are typically assemblages or redevelopment parcels.

R-OD (Residential Overlay District): Applied to specific neighborhoods to preserve character. Additional design standards, height limits, and use restrictions may apply. Consult district-specific overlay standards.

Investor implication: R-OD zones add regulatory complexity. North End and East End have active overlays. Acquisition due diligence must include overlay review. Design review timelines extend project schedules.

Up to two accessory dwelling units permitted per lot in all residential zones. Maximum size: 900 sq ft or 70% of primary dwelling floor area, whichever is less. Junior ADUs up to 500 sq ft permitted within primary structure. No parking required within 1/2 mile of frequent transit service.

Investor implication: ADU allowances significantly increase income potential on single-family parcels. Two-ADU strategy is viable on larger lots (7,000+ sq ft). Pre-approved plans reduce permitting risk and timeline.

Duplexes permitted by right in R-1C, R-2, and R-3 zones on conforming lots. Minimum lot size requirements apply per district. Each unit must meet minimum habitable floor area of 600 sq ft.

Investor implication: Duplex-by-right in R-1C and higher zones eliminates conditional-use permitting. Acquisition targets are R-1C lots at or above 5,000 sq ft. Duplex + ADU combinations maximize density on single parcels.

Minor land divisions (lot splits) permitted for divisions creating four or fewer lots. Each resulting lot must meet minimum dimensional standards for the underlying zone. No new public streets required for minor divisions.

Investor implication: Minor land division is the fastest path to lot multiplication on oversized parcels. Target parcels are 14,000+ sq ft in R-1B zones (allows 2-lot split) or 10,000+ sq ft in R-1C zones. No subdivision plat required.