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Centennial, CO Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified August 2026

ADU rules in Centennial, CO, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

ADUs per lot: One, single-family lots only
Size cap: 50% of principal home footprint
Detached ADU height: 17 ft. max
Registration: Required if non-owner-occupied; renews annually

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Colorado under recent ADU streamlining laws. The Centennial, CO rules below cover local size, height, and setback requirements.

Summary

Centennial allows one accessory dwelling unit per single-family lot, capped at 50% of the principal home's footprint and 17 feet tall if detached, with mandatory registration for non-owner-occupants.

b.ADUs are permitted only on a lot containing one single-family detached dwelling....c.Only one ADU shall be permitted per single-family detached dwelling....a.Size. An ADU shall not exceed fifty percent (50%) of the footprint of the principal dwelling unit or the total size of an attic or basement area (including any internal stairwell providing access) where additional construction that would expand those footprints is not occurring....iii.The maximum height of a detached ADU is seventeen (17) feet.

Source: Centennial ADU ProgramView official code

Full Breakdown

LDC § 12-3-603(H) permits one ADU per lot containing a single-family detached dwelling; it can't be sold separately from the principal home or platted onto its own lot. An ADU's habitable area can't exceed 50% of the principal dwelling's footprint (or an existing attic or basement's size), and a detached ADU tops out at 17 feet, measured the same way as the principal dwelling's height. Owners who won't occupy either unit as their primary residence must register the ADU with Community Development before occupancy, mail notice to adjacent property owners, and renew registration annually.

Violations & Fines

Occupying an unregistered ADU, or failing to renew registration or notify adjacent owners as required, is a Code violation: each day of noncompliance is a separate offense under § 12-3-603(H)(8).

Frequently Asked Questions

Can I build an accessory dwelling unit in Centennial?

Yes, one ADU per lot with a single-family detached home, capped at 50% of the principal home's footprint and 17 feet tall if detached, per LDC § 12-3-603(H).

Do I have to register my ADU with the City?

Only if neither you nor a family member will occupy the principal home or the ADU as a primary residence: then registration and annual renewal with Community Development are required.

Sources & Official References

[1]Centennial, CO Municipal Code — Land Development Code (Municode Library)

Other rules in Centennial

Noise Ordinances: Construction HoursSome Restrictions Shed & Carport RulesSome Restrictions Noise Ordinances: Amplified Music & Outdoor SoundSome Restrictions Parking Rules: EV ChargingSome Restrictions Parking Rules: Loading ZonesSome Restrictions Fence Regulations: Retaining WallsSome Restrictions Fire Regulations: Wildfire ZonesSome Restrictions

All Centennial rules

How Centennial compares: Easiest Cities to Build an ADU·Compare Centennial to another location·View the Colorado accessory structures overview

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ADU Rules in Nearby Cities

How other cities in Arapahoe County handle adu rules.

Aurora, CO