Boulder, CO Short-Term Rentals: Night Caps (2026)
Key Facts
- ADU night cap
- 120 days per calendar year
- Applies to
- Accessory dwelling units only, not principal homes
- Eligibility cutoff
- Unit legally established by February 1, 2019
- One unit at a time
- Either the ADU or the principal unit, not both
- Occupancy standard
- Follows Subsection 9-8-5(b), not the general STR rule
- New licenses
- Closed since February 1, 2019
Summary
An accessory dwelling unit rented as a short-term rental in Boulder is capped at 120 nights a year. Section 10-3-19(o)(5) sets that limit only for ADUs; it does not apply to a principal home rented short-term, which faces no separate day cap in the ordinance.
(5)An accessory dwelling unit may not be rented as a short-term rental for more than one hundred twenty days in any calendar year;
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Municipal Code: Supplement 167 Update 3).
Full Breakdown
Section 10-3-19(o) governs short-term rental of accessory dwelling units and, separately, of a principal dwelling unit on a lot that also has an accessory unit. Before any day-count applies, the ADU (or principal unit) must satisfy several threshold conditions: both the accessory unit and the principal unit had to be legally established by February 1, 2019, under paragraph (o)(1); the unit needs a current, valid short-term rental license under paragraph (o)(2); and only one of the two units on the lot, either the accessory unit or the principal unit, may be licensed or used as a rental at a time, under paragraphs (o)(3) and (o)(4).
C. 1981. Licensing for these units closed to new applicants after February 1, 2019, under paragraph (o)(7)(A); a detached accessory unit's applicant must also submit a structural inspection report under paragraph (o)(7)(B), and the city's energy efficiency standards in Property Maintenance Code Appendix C apply to any detached accessory unit licensed for short-term rental under paragraph (o)(7)(C).
Violations & Fines
Renting a licensed accessory dwelling unit as a short-term rental beyond 120 days in a calendar year breaches Section 10-3-19(o)(5) and exposes the operator to the escalating civil penalty schedule in Section 10-3-16(a)(1): $150, $300, then $1,000 for repeat violations of the same provision, plus possible license revocation. Licensing both the accessory unit and the principal unit as rentals at the same time also violates paragraphs (o)(3) and (o)(4).
Frequently Asked Questions
How many nights can I short-term rent my Boulder ADU?
Does the 120-day cap apply to my main house too?
Can both my ADU and my house be short-term rentals at once?
When did this 120-day ADU rule take effect?
Sources & Official References
Other rules in Boulder
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