ADU Impact Fees: Thornton vs Westminster
How do adu impact fees rules compare between Thornton, CO and Westminster, CO?
Thornton, CO
Adams County
Thornton collects development impact fees for new dwelling units through the City Development Department and Thornton Water/Infrastructure Division. ADU permits typically trigger a building permit fee scaled to valuation under Chapter 10, plan-review fees, Thornton Water/sewer tap or System Development Fees, drainage and traffic impact fees per the annual Thornton Fee Schedule, and use-tax on construction materials at the Thornton sales tax rate. Thornton has not adopted a categorical ADU fee waiver, though HB24-1152 encourages waivers for small or affordable ADUs through the Colorado DLG ADU Supportive Jurisdiction program.
View full Thornton rules →Westminster, CO
Adams County
No data available yet for Westminster.
Key Facts Comparison
| Fact | Thornton | Westminster |
|---|---|---|
| Building Permit Fee | Scales with valuation (Code Ch. 10) | - |
| Water System Dev Fee | $20k+ separate meter; $0 shared | - |
| Thornton Use Tax | 3.75% of construction materials | - |
| Categorical ADU Waiver | Not adopted | - |
| School Impact Fee | $0 (not authorized in CO) | - |
| DLG Waiver Program | ADU Supportive Jurisdiction (optional) | - |
Highlighted rows indicate differences between cities.
Thornton FAQ
Does Thornton waive ADU impact fees?
Not categorically. The city follows the standard residential fee schedule in Code of Ordinances Chapter 10 and the annual Thornton Fee Schedule, including building permit, plan-review, water/sewer System Development Fees, drainage, and traffic impact fees. The biggest cost saver is sharing the primary dwelling's water and sewer service rather than pulling a separate tap. HB24-1152 encourages waivers for small ADUs through the Colorado DLG.
How much should I budget for fees on a typical 700 sq ft Thornton ADU?
Budget $4,000-$8,000 in permit and plan-review fees if sharing utilities with the main house. Add tens of thousands per separate water and sewer tap if needed - Thornton Water's System Development Fees are among the highest in metro Denver because of the raw-water requirement. Use-tax at 3.75% of materials applies. Pull the current schedule from City Development before designing.
Westminster FAQ
No FAQs available.
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