ADU Owner Occupancy: Thornton vs Westminster
How do adu owner occupancy rules compare between Thornton, CO and Westminster, CO?
Thornton, CO
Adams County
Thornton's STR ordinance (Code Sections 18-54 and 18-174) already requires short-term-rental use of an ADU to be at the licensee's primary residence, which functions as an owner-occupancy condition when an ADU is used as an STR. The Thornton Development Code historically conditioned some ADU types on accessory residential use rather than absolute owner occupancy. Colorado HB24-1152, operative June 30, 2025, preempts owner-occupancy requirements on ADUs in subject jurisdictions including Thornton; the city is amending the TDC to comply.
View full Thornton rules →Westminster, CO
Adams County
No data available yet for Westminster.
Key Facts Comparison
| Fact | Thornton | Westminster |
|---|---|---|
| Long-Term ADU Owner Occupancy | Cannot be required (HB24-1152) | - |
| STR Primary-Residence Rule | Code 18-54/18-174 (still applies) | - |
| State Preemption | HB24-1152 (eff. 6/30/2025) | - |
| Subject Jurisdiction | Yes (DRCOG MPO) | - |
| Deed Restriction | Not currently recorded | - |
| TDC Status | Amendments pending | - |
Highlighted rows indicate differences between cities.
Thornton FAQ
Can I rent both my Thornton main house and ADU without living on the lot?
For long-term leases of 30+ days, yes. Colorado HB24-1152 preempts any city requirement that the owner live on the lot to operate an ADU. For short-term rental (under 30 days), Thornton Code 18-54 and 18-174 still require the STR licensee to occupy the property as a primary residence, which Thornton may continue to enforce as an STR licensing rule independent of the ADU itself.
Does HB24-1152 affect ADUs already built in Thornton?
Yes. HB24-1152 applies to existing and new ADUs in subject jurisdictions. Thornton may not enforce owner-occupancy as a condition of ADU operation in conflict with C.R.S. 29-32-101 et seq. once the operative date passed on June 30, 2025, even on permits issued earlier. Recorded deed restrictions from older ADU approvals that include owner-occupancy clauses are likely unenforceable to that extent.
Westminster FAQ
No FAQs available.
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