What is the 500 to 750 square foot size protection in Colorado's ADU law?
✓ Verified against code · August 19, 2026
HB24-1152 bars design and dimensional standards that would prevent an ADU anywhere in the 500 to 750 sq ft range — a city can't cap ADUs so small that a legitimate 750 sq ft unit becomes impossible. Several city codes appear to conflict with that floor: Arvada caps ADUs on lots under 6,000 sq ft at 600 sq ft, Aurora sets a flat 650 sq ft cap, and Greeley's 60%-of-home formula can compute below the statute's protected range on smaller homes. Westminster and Fort Collins, by contrast, explicitly guarantee up to 750 sq ft for owners of smaller homes, matching the statute's protection directly.
Citation: C.R.S. 29-35-402(18)
How current is this?
Colorado’s ADU rules run under HB24-1152 (2024). HB24-1152 (codified at C.R.S. 29-35-401 through 29-35-405) required every Colorado city or town of 1,000+ residents inside a metropolitan planning organization to allow one ADU wherever a single-family home is allowed, through administrative approval, by June 30, 2025 — banning ongoing owner-occupancy mandates (an at-application residency check is allowed), most new-parking requirements, and design standards that would block an ADU in the 500–750 sq ft range. Note the contrast with Washington: one ADU per lot, not two. We verified this answer against primary sources on August 19, 2026, and every change we catch is logged in the changelog.
More Colorado ADU questions
- What is HB24-1152?
- Which Colorado cities are not complying with the ADU law?
- Does Colorado allow two ADUs per lot?
- What happened to Lakewood's zoning code?
- How big can an ADU be in Colorado?
- Do Colorado cities require ADU owners to live on the property?
- Can Colorado cities require parking for an ADU?
- What does home rule mean for Colorado's ADU law?
- What do Colorado ADU permits cost?
- How long does it take to get an ADU permit approved in Colorado?
- Can I rent out my Colorado ADU short-term on Airbnb?
Not legal advice — local ordinances can go further than the state floor. The citation above points at the governing statute; check your city’s code for the specifics.