Longmont, CO Accessory Structures: Carport Rules (2026)

Carports — covered, open-sided structures used to shelter vehicles — are treated as detached accessory structures under LMC Title 15. Under LMC Title 16 and the International Residential Code, a carport with a roof area exceeding 120 square feet requires a building permit, foundation design, and engineered anchorage for the post-and-beam system. Required setbacks per LMC § 15.03.080.C (accessory structure standards) are at least 5 feet from rear and side property lines, and the carport must be located behind the front facade of the principal dwelling. The carport counts against the 75% total accessory structure cap relative to the principal structure's floor area. Carports may not be permanently enclosed with walls without a separate permit converting them to a garage, which triggers full IRC garage standards including a fire separation between the structure and any habitable space. Carports attached to the principal dwelling are treated as part of the dwelling for setback purposes — they must meet the principal-building setbacks (typically 15 ft front in R-SF, 5 ft side, 20 ft rear without alley). Carports placed in front yards or used to encroach into required setbacks are prohibited.