Long-term rental of an ADU (30+ day leases) is allowed in Thornton with no city license beyond the ADU permit and no city-imposed cap on rental volume. Short-term rental (under 30 days) of an ADU requires a Thornton STR license under Code Sections 18-54 and 18-174 (Ord. 2020-099) at $180/year, $1M liability insurance, primary-residence operation, and collection of Thornton lodging tax plus the State of Colorado lodger's tax. HB24-1152 preempts ADU-specific rental volume caps as of June 30, 2025.
Thornton's residential rental framework distinguishes long-term and short-term use. Long-term ADU rentals (leases of 30 or more consecutive days) require no city license and are governed by Colorado landlord-tenant law, including the warranty of habitability (C.R.S. 38-12-503) and the 2024 just-cause eviction protections (HB24-1098). Thornton does not maintain a long-term rental registry. Short-term rental of an ADU triggers Thornton's STR ordinance (Code Sections 18-54 and 18-174, adopted by Ord. 2020-099, effective February 1, 2021). The operator must obtain an annual STR license at $180 (paid through the GovOS/MUNIRevs portal at thornton.munirevs.com), carry at least $1 million in liability insurance, list only the licensee's primary residence, hold one STR license per person, post the license number on every advertisement, and collect Thornton lodging tax plus the Colorado state lodger's tax (currently 4.25%). The primary-residence rule has the practical effect of limiting STR use to roughly 182 nights or fewer per year because the licensee must occupy the property more than 50% of the year. Colorado HB24-1152 (effective June 30, 2025) prohibits Thornton from capping ADU rental volume by ordinance, but does not preempt the city's STR licensing scheme generally; the primary-residence STR rule remains in place.
Operating an unlicensed STR in an ADU violates Thornton Code 18-54/18-174 and is grounds for license revocation, advertisement takedown, and Municipal Court fines up to $2,650 per day under Section 38-1. Renting a non-primary residence as an STR is prohibited outright. Failure to remit lodging tax accrues interest and penalties and personal operator liability. Long-term rental violations (e.g., habitability failures) are enforced under state law and through civil court, not the Thornton STR program.
Thornton, CO
Thornton prohibits storing abandoned, inoperable, or unregistered vehicles on public streets or visible on private property. Vehicles may be tagged and towed...
Thornton, CO
Thornton regulates electric vehicle charging infrastructure for residential and commercial properties. Building codes may require EV-ready parking in new con...
Thornton, CO
Thornton regulates overnight parking on public streets. Many areas restrict parking between certain hours or require permits for overnight street parking.
Thornton, CO
Thornton requires pool barriers meeting safety codes to prevent drowning. Fences must be at least 4 to 5 feet tall with self-closing, self-latching gates.
Thornton, CO
Thornton requires permits for retaining walls above a certain height, typically 4 feet. Engineering review may be required for taller walls.
Thornton, CO
Thornton restricts or prohibits intentional feeding of wildlife including deer, coyotes, and bears. Feeding wildlife creates public safety hazards and nuisan...
See how Thornton's adu rental restrictions rules stack up against other locations.
Help us keep this page accurate. If you notice an error or outdated information, let us know.