Aurora ADU rules

✓ Verified against code · August 19, 2026

Current rules under UDO §146-3.3.6.G (2018-era rules carried into the 2019 UDO), adopted by No HB24-1152 compliance ordinance exists, in effect since September 21, 2019. Aurora is the state's highest-profile ADU holdout: its council voted a staff-drafted compliance ordinance down in June 2025, the state formally identified Aurora as non-compliant with the ADU law in October 2025, and as of August 2026 the codified rules are still the restrictive 2018 regime. Where the code conflicts with C.R.S. 29-35-403, state law controls on paper — but the city's counter still applies its own code, and only 9 ADUs have been permitted since 2018.

Common questions, answered from the code

Can I build an ADU in Aurora?

Under the city's code as written: only a detached, 650 sq ft ADU on an alley-served lot in the Original Aurora subdistricts, through a public hearing, with the owner living on site. State law (C.R.S. 29-35-403) has required much more since June 30, 2025, and the state formally flagged Aurora as non-compliant in October 2025 — but the code hasn't been amended, so expect friction at the counter and get anything the city tells you in writing.

UDO §146-3.3.6.G; DOLA Oct 2025 determination · Permalink

Is Aurora breaking Colorado's ADU law?

The state says yes: Colorado's October 2025 compliance review named Aurora among the jurisdictions not complying with the ADU statute, after its council voted a compliance ordinance down in June 2025. A corrective ordinance was in staff drafting as of July 2026 but nothing has been adopted. We re-check every pass and will log the fix the day it lands.

DOLA Oct 7, 2025 release; council record 6/9/2025 · Permalink

When will Aurora's ADU rules change?

Unknown — council directed staff in July 2026 to draft an ordinance allowing one internal, attached, or detached ADU on most single-family lots with administrative review, but no ordinance number, hearing date, or adoption exists yet. Any guide describing 'new Aurora ADU rules' before an ordinance passes is ahead of the facts.

Council study session 7/13/2026 · Permalink

Does Aurora's lawsuit against the state cover ADUs?

No — Aurora joined five other home-rule cities suing over different housing laws (occupancy limits, transit-oriented density, parking) and an executive order. The city is 'not currently fighting' the ADU law in court; it just hasn't complied with it.

Six-city suit, Denver District Court (filed 5/19/2025) · Permalink

The rules at a glance

ADUs allowed per lot	As codified: one detached ADU per single-family home — attached and internal ADUs prohibited — and only in the Original Aurora MU-OA subdistricts (OA-R1, OA-R2, OA-RMU) on alley-served lots, plus the Painted Prairie master-planned area under its own development plan. State law requires far more; the code hasn't caught up.UDO §146-3.3.6.G.1; Table 3.2-1; contrast C.R.S. 29-35-403(1)
Maximum size	650 sq ft — below the 750 sq ft the statute protects, one of several provisions in apparent conflict with state law.UDO §146-3.3.6.G.1.h; contrast C.R.S. 29-35-402(18)
Detached ADU height	No taller than the principal dwelling, and never more than 24 ft.UDO §146-3.3.6.G.1.i, .p
Detached ADU setbacks	Rear yard only; 5 ft side, 5 ft rear, 3 ft from the alley. An ADU atop an existing garage may keep the garage's setbacks.UDO §146-3.3.6.G.1.o; §146-4.2.3.F.1
Off-street parking	One additional alley-accessed off-street space — and alley service is itself a prerequisite for the use. Both likely exceed what the statute permits.UDO §146-3.3.6.G.1.a, .k; contrast C.R.S. 29-35-403(2)(a), (3)
Owner-occupancy	Still codified: the owner must occupy the primary dwelling or the ADU. Preempted on paper by state law since June 30, 2025, but not repealed.UDO §146-3.3.6.G.1.l; contrast C.R.S. 29-35-403(2)(b)
Lot coverage / floor area	Lot must exceed 6,000 sq ft; the ADU may cover no more than 50% of the rear yard, and 360 sq ft of usable private open space (minimum dimension 10 ft) must remain.UDO §146-3.3.6.G.1.e, .g
Permit path & timeline	Conditional use with a Planning Commission public hearing — the opposite of the administrative approval state law mandates. No published timeline.UDO Table 3.2-1; contrast C.R.S. 29-35-403(1)

Worth knowing

The numbers tell the story: 9 ADUs permitted (5 built) since 2018, while 262 inquiries between 2023 and mid-2026 fell outside the eligible zones.
Council rejected the staff-drafted compliance ordinance on June 9, 2025 — the exact tally is contested (press reported 6–2 while admitting the clerk never announced it; a meeting-video summary says 7–2), so we publish the rejection without a number; a July 2026 study session directed staff to draft a broader fix (internal/attached/detached ADUs on most single-family lots, administrative review) — nothing adopted yet.
Aurora is a plaintiff in the six-city home-rule lawsuit against the state, but that suit targets other housing laws (HB24-1313, HB24-1304, an executive order) — not the ADU statute itself.
Aurora is not a state-certified ADU-supportive jurisdiction, which affects its access to related state grant programs.
How the city treats an application citing state law directly (outside the MU-OA zones) is publicly unstated — the city's 2024 memo says existing requirements remain until the UDO is amended.

On our watchlist

The corrective ordinance directed at the July 13, 2026 study session — this page goes materially stale the day it's adopted; it's the top item on our watchlist.

The six-city home-rule lawsuit (other housing statutes) remains pending and could reshape the preemption landscape.

Check your parcel

The rules above are citywide — what you can build depends on your lot’s zone, size, and setbacks. Look yours up on the official viewers:

Primary sources

Other Colorado cities

Arvada · Boulder · Colorado Springs · Denver · Fort Collins · Greeley · Lakewood · Longmont · Pueblo · Thornton · Westminster

Not legal advice. Every fact above cites the code section it comes from — check the cite, or ask your city’s planning department to confirm your specific lot. Spotted an error or a new ordinance? See about to reach us; corrections are logged in the changelog.