Summary of Nampa City Code §10-7 (Accessory Dwelling Units) as it applies in Nampa.
Code evolves continuously. Verify at the official source before any development decision.
Applicable code
Code references active as of publication. Verify current standards at the official source before any development decision.
Accessory dwelling units are permitted in all single-family residential zoning districts (R-1, R-2, R-3, RD) subject to the standards in Section 10-7.
Investor implication: ADUs are permitted citywide in single-family zones. No conditional-use permit required for standard ADUs meeting dimensional standards.
Verify at Nampa City Code Title 10 →One accessory dwelling unit is permitted per single-family lot.
Investor implication: One ADU per lot. Idaho SB 1354 (effective 2026-07-01) requires cities to allow at least one ADU per lot; Nampa's current ordinance already complies.
Verify at Nampa City Code Title 10 →The accessory dwelling unit shall not exceed 800 square feet of gross floor area or 50% of the gross floor area of the primary dwelling, whichever is less.
Investor implication: Size cap is the lesser of 800 sq ft or 50% of primary dwelling. On a 1,600 sq ft house, maximum ADU is 800 sq ft. On a 1,200 sq ft house, maximum ADU is 600 sq ft.
Verify at Nampa City Code Title 10 →Accessory dwelling units may be attached to or detached from the primary dwelling. Detached ADUs must meet the accessory structure setback requirements of the underlying zone.
Investor implication: Both attached and detached ADUs are permitted. Detached ADUs follow accessory structure setbacks (typically 5 feet side/rear in R-1 and R-2 zones).
Verify at Nampa City Code Title 10 →Either the primary dwelling or the accessory dwelling unit must be occupied by the owner of the property.
Investor implication: Owner-occupancy is required in either the primary or the ADU. Idaho SB 1354 (effective 2026-07-01) prohibits cities from requiring owner-occupancy. Nampa's ordinance will need to be amended by July 1, 2026 to comply with state law.
Verify at Nampa City Code Title 10 →One additional off-street parking space is required for the accessory dwelling unit.
Investor implication: One parking space required per ADU. No transit-proximity waiver in current code. Verify lot dimensions can accommodate the additional parking space before acquisition.
Verify at Nampa City Code Title 10 →The accessory dwelling unit shall be designed to be compatible with the primary dwelling in terms of materials, colors, and architectural style.
Investor implication: Design compatibility is required but not defined by specific standards. Expect staff discretion during plan review. Match primary dwelling materials and roof pitch to minimize review friction.
Verify at Nampa City Code Title 10 →Process
Typical sequence for this pathway. Timelines are ranges; each parcel varies.
Confirm the lot is in a single-family residential zone (R-1, R-2, R-3, RD). Verify the primary dwelling exists and is legally established. Measure lot dimensions to confirm space for the ADU footprint, setbacks, and the required additional parking space.
City staff reviews plans for compliance with zoning standards (size, setbacks, parking, design compatibility), building code, and fire code. Corrections may be required.
After final inspection approval, the city issues a certificate of occupancy. The ADU is now legally habitable.
Renew analysis
ADUs are permitted citywide in single-family zones. No conditional-use permit required for standard ADUs meeting dimensional standards.
One ADU per lot. Idaho SB 1354 (effective 2026-07-01) requires cities to allow at least one ADU per lot; Nampa's current ordinance already complies.
Size cap is the lesser of 800 sq ft or 50% of primary dwelling. On a 1,600 sq ft house, maximum ADU is 800 sq ft. On a 1,200 sq ft house, maximum ADU is 600 sq ft.
Both attached and detached ADUs are permitted. Detached ADUs follow accessory structure setbacks (typically 5 feet side/rear in R-1 and R-2 zones).
Owner-occupancy is required in either the primary or the ADU. Idaho SB 1354 (effective 2026-07-01) prohibits cities from requiring owner-occupancy. Nampa's ordinance will need to be amended by July 1, 2026 to comply with state law.
One parking space required per ADU. No transit-proximity waiver in current code. Verify lot dimensions can accommodate the additional parking space before acquisition.
Design compatibility is required but not defined by specific standards. Expect staff discretion during plan review. Match primary dwelling materials and roof pitch to minimize review friction.
Nampa's owner-occupancy requirement will be unenforceable after July 1, 2026. Expect a city ordinance amendment in Q2 or Q3 2026 to bring local code into compliance. Investors acquiring ADU-capable lots before July 1, 2026 should model both scenarios: owner-occupied (current) and non-owner-occupied (post-SB 1354).