Nampa Duplex Guide

Duplexes are permitted by right in RD (Residential Duplex) and RM (Residential Multi-Family) zoning districts. Conditional use permits may be required in certain R-1 and R-2 districts subject to specific lot size and compatibility standards.

Investor implication: RD and RM zones offer the clearest path to duplex development without discretionary review. R-1 and R-2 conditional use paths add 60-90 days and hearing risk to the timeline.

RD zone: minimum 6,000 square feet per lot. RM zone: minimum 5,000 square feet per lot. Conditional use in R-1/R-2: minimum 8,000 square feet.

Investor implication: RM-zoned lots under 6,000 sq ft can pencil duplex construction where RD cannot. Verify zoning before acquisition on any lot between 5,000-6,000 sq ft.

Front setback: 20 feet. Side setback: 5 feet (interior), 10 feet (corner). Rear setback: 20 feet. Alley-facing structures: 10-foot rear setback permitted.

Investor implication: Alley-facing lots gain 10 feet of buildable depth. On a 100-foot-deep lot, this is the difference between a 1,400 sq ft footprint and a 1,600 sq ft footprint at standard side setbacks.

Two off-street parking spaces required per unit (four total for a duplex). Tandem parking permitted. Garage spaces count toward requirement.

Investor implication: Four-space requirement constrains site design on narrow lots. Tandem allowance recovers some flexibility but limits rental appeal for two-car households.

Maximum lot coverage: 40% in RD zones, 50% in RM zones. Coverage includes all structures, driveways, and impervious surfaces.

Investor implication: On a 6,000 sq ft RD lot, maximum building footprint is 2,400 sq ft minus driveway area. RM's 50% allowance adds 600 sq ft of buildable area on the same lot size.

Maximum height: 35 feet in RD zones, 45 feet in RM zones. Height measured from average finished grade to highest roof point.

Investor implication: 35-foot RD limit accommodates two-story construction with standard 9-foot ceilings and typical roof pitch. Three-story construction requires RM zoning.