When does a ADU need a building permit in Denver?

Every ADU needs a building permit and a Certificate of Occupancy before anyone lives in it.

How far from the property line can a ADU go in Denver?

Side setback: 3 ft on lots 40 ft wide or less; 5 ft on wider lots. Setbacks vary by zoning district; check your exact lot for the district that applies.

Where do I apply for a ADU permit in Denver?

Apply through Denver e-permits (Accela), or call 311 (720-913-1311).

Do you need a permit for an ADU in Denver, CO?

Yes. The Denver Zoning Code sets the ADU's height, size and placement, and zoning review checks it.

ADUs are allowed in every Denver zone district that allows a new single-unit home.

Only a licensed contractor can pull an ADU permit; homeowner permits aren't allowed.

Rules last checked by a person on October 19, 2026. Guidance only; confirm with Denver before you build.

Check your exact lot

Setbacks depend on your zoning district, and a flood zone can change the permit answer. Enter your address to see both.

Permits a ADU can need in Denver

Permit	When it applies
Zoning permit	The Denver Zoning Code sets the ADU's height, size and placement, and zoning review checks it.
Building permit	Every ADU needs a building permit and a Certificate of Occupancy before anyone lives in it.
Sewer use and drainage permit (SUDP)	All new ADUs need zoning, building and sewer use and drainage permits in Denver.
Floodplain development permit	If the lot is in a FEMA special flood hazard area, all development there needs a permit.

Urban (U-) single unit, two unit and row house

ADU standards in Urban (U-) single unit, two unit and row house
Height	2 stories, 24 ft
Location	Rear 35% of the lot depth
Side setback	3 ft on lots 40 ft wide or less; 5 ft on wider lots
Rear setback	5 ft (0 ft on an alley when garage doors don't face it)
Footprint	864 sq ft on lots of 7,000 sq ft or less; 1,000 sq ft on larger lots

All rules for Urban (U-) single unit, two unit and row house

Urban Edge (E-) single unit, two unit and row house

ADU standards in Urban Edge (E-) single unit, two unit and row house
Height	Option A: 1 story, 17 ft. Option B: 2 stories, 24 ft
Location	Rear 35% of the lot depth
Side setback	3 ft on lots 40 ft wide or less; 5 ft on wider lots
Rear setback	5 ft with an alley or street behind; otherwise 5 ft (Option A) or 12 ft (Option B)
Footprint	864 sq ft on lots of 7,000 sq ft or less; 1,000 sq ft on larger lots

All rules for Urban Edge (E-) single unit, two unit and row house

Suburban (S-) single unit

ADU standards in Suburban (S-) single unit
Height	Option A: 1 story, 17 ft. Option B: 2 stories, 24 ft
Location	Rear 50% of the lot depth
Side setback	3 ft (lots 25 ft wide or less), 5 ft (under 62 ft), 7.5 ft (62 ft or wider)
Rear setback	10 ft (Option A) or 20 ft (Option B)
Footprint	864 sq ft on lots of 7,000 sq ft or less; 1,000 sq ft on larger lots

All rules for Suburban (S-) single unit

Suburban (S-) row house

ADU standards in Suburban (S-) row house
Height	2 stories, 24 ft
Location	Rear 50% of the lot depth
Side setback	3 ft on lots 25 ft wide or less; otherwise 5 ft
Rear setback	5 ft

All rules for Suburban (S-) row house

Local details

A licensed contractor must apply; Denver doesn't issue homeowner permits for ADUs.
Only one ADU per primary home, and the ADU needs its own address.
In single-unit districts the owner must live in the main house when applying (not required when both are built at the same time).
Call 811 at least a few days before you dig footings or post holes. Utility locating is free.
HOA covenants and deed restrictions can be stricter than city rules. Check yours before you build.

How to apply

Questions people ask

When does a ADU need a building permit in Denver?: Every ADU needs a building permit and a Certificate of Occupancy before anyone lives in it.
Do I also need a zoning permit for an ADU in Denver?: The Denver Zoning Code sets the ADU's height, size and placement, and zoning review checks it.
How far from the property line can a ADU go in Denver?: Side setback: 3 ft on lots 40 ft wide or less; 5 ft on wider lots. Setbacks vary by zoning district; check your exact lot for the district that applies.
Where do I apply for a ADU permit in Denver?: Apply through Denver e-permits (Accela), or call 311 (720-913-1311).

Sources

Denver CPD, Permitting an Accessory Dwelling Unit (ADU). Checked 2026-10-19.
ADUs are allowed in all zone districts that allow new single unit dwellings. ADUs must be built by a licensed contractor... Only one ADU is allowed per primary dwelling unit.
44 CFR 59.1, definition of development (NFIP). Checked 2026-10-19.
Development means any man-made change to improved or unimproved real estate, including but not limited to buildings or other structures...
44 CFR 60.3, floodplain management criteria. Checked 2026-10-19.
Require permits for all proposed construction or other development in the community...