A second house in your back garden. The rules changed.
If someone told you no before 2025, ask again. Colorado’s ADU law reset the floor under every city on the Front Range, and several of them have not updated their own web pages yet.
Your city cannot make this a public hearing.
An ADU application is decided administratively, on objective standards. Not on whether it is compatible, or harmonious, or in keeping with community character — those tests are specifically prohibited now. There is no public hearing, and one cannot be added. There is no permanent owner-occupancy commitment and no deed restriction. In most cases no new parking space is required. And somewhere between 500 and 750 square feet has to be allowed to you.
That is the floor. Your city can be more generous. Several are. None of them can be less.
Same state law. Nine different answers.
We keep this because the number that decides your design is local, and it moves. Where we could not verify a rule, we say so instead of guessing.
Wheat Ridge is the only DOLA-certified ADU Supportive Jurisdiction on that list. If you live there, you have the easiest path on the Front Range.
Denver
- Size cap
- Varies by zone; no citywide cap
- Owner-occupancy
- Removed
- Note
- ADU-eligible land went from about 36% to 70% of the city in December 2024
Wheat Ridge
- Size cap
- 1,000 sq ft or 50% of the house, whichever is more restrictive
- Owner-occupancy
- Not required
- Parking
- None
Englewood
- Size cap
- 800 sq ft, permitted in eight districts
- Owner-occupancy
- Not required
- Parking
- None
Arvada
- Size cap
- 600 / 850 / 1,000 / 1,200 sq ft by lot size; also capped at 40% of primary living space
- Owner-occupancy
- Not verified — we confirm before design
- Parking
- Required; ratio not verified
Centennial
- Size cap
- 50% of the principal dwelling footprint; detached height capped at 17 ft
- Owner-occupancy
- Not required; absentee owners register
- Parking
- One space required — in live tension with state law
Golden
- Published cap
- 800 sq ft or 50%, owner-occupancy, one space, three occupants
- The problem
- That page makes no reference to the 2024 state law
- Our position
- We treat it as out of date and confirm before design
Lakewood
- Status
- New code effective January 2026, repealed at the April 2026 ballot, city pages not updated
- Our position
- We will not quote you a Lakewood number we cannot stand behind
Cherry Hills Village
- Where
- R-1 and R-2 only
- Constraints
- 75 ft accessory setbacks and a 12′6″ bulk plane
Highlands Ranch
- Status
- The county’s 2025 ADU resolution amends districts Highlands Ranch is not zoned under, and the PD guide is silent
- Our position
- Whether an ADU is permitted here is genuinely unresolved
The building is the cheap part. The ground and the services are not.
A detached ADU is a new structure, which means a new foundation, a new service run for water, sewer, gas and power, and in most cases a new electrical panel on the main house. On a sloping lot the foundation and the drainage decide the budget before anyone picks a finish.
Two towns will also shape the building itself before you have drawn it: Wheat Ridge and Englewood both apply bulk plane — an angled envelope over the top of your setbacks — and Centennial requires the ADU to match the main house on at least three of six attributes: roof pitch, cladding, windows, doors, architectural features, colour palette.
Arvada’s 2024 code also permits a homeowner to self-build an ADU. We will tell you honestly when that is the better economics for you and when it is not. We documented a Denver pop-top with an ADU on this project page.
- Feasibility and zoning check before you spend on design
- Survey and site plan
- Foundation and drainage design for your actual slope
- Utility service runs and panel upgrade
- Framing through finish
- Administrative permit submittal and inspections
- One contract, one accountable team
Detached ADU questions we get asked.
I was told no a few years ago. Is that still the answer?
Probably not, if you are in Denver. The December 2024 rezoning roughly doubled the amount of the city where an ADU is allowed and removed the owner-occupancy requirement. It is worth asking again.
Does someone have to live in the main house?
Not as a permanent commitment — the state removed that. Centennial asks absentee owners to register. Golden’s published page still says otherwise; we treat that page as out of date and confirm before design.
Will I need another parking space?
Usually not. Centennial still asks for one, which sits awkwardly against the state law. Wheat Ridge and Englewood require none.
How small can it be?
Your city has to allow you somewhere between 500 and 750 square feet whatever its own cap says. Arvada’s cap scales with your lot, up to 1,200.
Tell us the address. We will tell you what is possible.
We check your zoning, your lot and your city’s current position before anyone draws anything. If the answer is no, you hear it on the phone, not after you have paid for design.
Prefer to talk now? Call (720) 637-2060
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