City or county? Find out which ADU rules apply to your property.
Boulder County has two very different ADU rulebooks, and the one that applies to you comes down to a single question: is your property inside a city or town, or is it unincorporated?
Why it matters
A Boulder mailing address does not mean city rules.
Mailing addresses follow post office routes, not city limits. Plenty of properties with a “Boulder, CO” address sit outside the city, on unincorporated county land. Gunbarrel is the example people run into most often. The two rulebooks differ sharply, so guessing is expensive.
- City of Boulder: Settled and permissive. ADUs are allowed by right in most zones, with a building permit and no separate approval step. See the rules.
- Unincorporated Boulder County: Restrictive today, and under review. The state ADU law does not reach unincorporated county land, and the county is rewriting its accessory dwelling rules. See the rules.
Your property tax bill, your water provider and your voter registration are all decent hints, but none of them is definitive. The county’s own property record is.
About two minutes
How to check your property.
An address lookup is coming to this page. Until then, the county’s own tool gives you the answer directly.
- 1
Open the county Property Search
Boulder County publishes a property lookup that covers every parcel in the county, incorporated or not.
- 2
Search your address
Enter the street address exactly as it appears on your tax bill. If nothing matches, try the parcel number instead.
- 3
Read the jurisdiction field
The record names the municipality a parcel sits in. If it names a city or town, that government writes your land use rules. If it names none, the parcel is unincorporated and the county Land Use Code governs.
- 4
Note the zoning district
The same record shows the zoning district. That is the first thing you will need on either rulebook.
Still not certain? Boulder County Community Planning and Permitting and the City of Boulder Planning and Development Services will both confirm which jurisdiction a parcel falls in. Ask them before you design anything.
Sources
- Boulder County Property SearchBoulder County
- Planning Frequently Asked QuestionsBoulder County
This page summarizes public rules for general information. It isn’t legal advice or a permit determination. Confirm requirements for your property with the City of Boulder or Boulder County before you design or build.
Not sure yet? Get updates anyway.
Tell us roughly where you are and we will send rule changes for that area. You can change it later.