Longmont, CO Accessory Structures: ADU Rental Restrictions (2026)
Key Facts
- Governing section
- Longmont Municipal Code § 15.02.080.D.2.c; E.3.g
- ADU short-term rental
- Outright banned as a short-term rental
- ADU sale rule
- Cannot be sold separately from principal dwelling
- Long-term rental
- Ordinary long-term ADU rental remains allowed
- Penalty
- Up to $500 fine, 90 days jail (§ 1.12.010)
Summary
Longmont bars accessory dwelling units from being used as short-term rentals outright, under Longmont Municipal Code section 15.02.080.D.2.c. A separate ADU standard in section 15.02.080.E.3.g also blocks selling an ADU apart from the main house, keeping accessory units tied to long-term, owner-linked occupancy rather than the short-term rental market.
c.Accessory dwelling units shall not be used as a short-term rental. ... g.Limit on sale, tenancy and occupancy.i.Accessory dwelling units shall not be sold separately from the principal dwelling.
Full Breakdown
Longmont's short-term rental subsection lists exactly which dwellings can be licensed as short-term rentals: a primary dwelling, or a resident's second or investment dwelling. Accessory dwelling units are deliberately left off that list. E, adopted and amended through Ordinance No. O-2021-36, Ordinance No. O-2023-10, Ordinance No. O-2025-35 and Ordinance No. O-2025-83, the last effective December 16, 2025. Those standards cap most ADUs at 500 to 800 square feet, unless the unit stays under 50 percent of the principal dwelling's finished above-ground area, and require an ADU to sit on the same lot as, and be accessory to, a single-family detached dwelling.
g adds a related but distinct restriction on tenancy: "Accessory dwelling units shall not be sold separately from the principal dwelling," meaning an ADU cannot be carved off into its own parcel or condo-style ownership even for long-term housing. Together, the two provisions keep an ADU functioning as accessory housing tied to its principal lot: not sold off on its own, and not run as a nightly or weekly rental. "
Violations & Fines
Operating an accessory dwelling unit as a short-term rental violates section 15.02.080.D.2.c directly; because ADUs are excluded from the dwellings eligible for a short-term rental license, no license can lawfully issue for one, making operation unlicensed activity under section D.3 and a development code violation under section 15.09.030. That carries the general penalty in section 1.12.010, up to $500.00 and 90 days in jail, plus civil penalties under chapter 2.97.
Frequently Asked Questions
Can I rent out my backyard ADU in Longmont as an Airbnb?
Can a Longmont accessory dwelling unit be sold or owned separately from the main house?
What happens if someone operates an unlicensed short-term rental in a Longmont ADU?
Sources & Official References
Other rules in Longmont
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ADU Rental Restrictions in Nearby Cities
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