Longmont, CO Building Setbacks & Zoning: Setback Rules (2026)

Longmont's residential dimensional standards are codified in LMC Chapter 15.03 (Dimensional Standards) with exception rules at § 15.03.080.C. Setbacks vary by zone: (a) Residential Single Family (R-SF): front yard dwelling 15 ft, front yard with alley garage access 10 ft, front-facing garage 20 ft, side yard (no street frontage) 5 ft, rear yard without alley 20 ft, rear yard abutting alley 6 ft; (b) Residential Mixed Neighborhood (R-MN): same as R-SF except rear yard without alley is 15 ft; (c) Residential Multifamily (R-MF): same as R-SF except rear yard without alley is 10 ft; (d) Residential Rural (R-RU): front yard 20 ft, side yard 10 ft, rear yard without alley 20 ft, rear yard abutting alley 6 ft. Corner lots are subject to front setbacks on both street-fronting sides. Decks less than 24 inches above grade may encroach into a required rear or side yard if uncovered and designed to accommodate lot drainage; decks 24 inches or higher must meet the principal-building setbacks. Detached accessory structures (sheds, detached garages, carports, ADUs) follow the accessory standard: at least 5 ft from rear and side property lines and behind the front facade of the principal building. Eaves, chimneys, bay windows, and similar architectural features may encroach into required yards by limited distances under § 15.03.080.C. Fences are regulated separately under the LDC fence standards.