About Boco ADU
A plain-English, sourced guide to accessory dwelling unit rules in Boulder County.
Who
Who runs this.
Boco ADU is run by [FOUNDER NAME]. [SHORT BIO]
Boco ADU is a Boulder County company working toward a local program for factory-built ADUs. That program does not exist yet, so this site sells nothing. There are no products here, no prices, no models and no manufacturers. When there is something to sell, we will say so plainly and you will still be able to read the rules for free.
Method
How the facts get here.
Every regulatory statement on this site lives in a data file, not in the page. Each one carries the official page it came from and the date a person last read that page. Both are shown to you: the source link sits beside the rule, and the review date sits at the top and bottom of every rules page.
We paraphrase official text rather than copying it, and we link out so you can read the original. Nothing here is written from memory or from another state’s rules.
When we are not certain of something, the site says it is being confirmed and names who we are confirming it with. It does not guess, and it does not show a number we have not checked. A build of this site fails if a rule is missing its source or its date, or if a page tries to state a figure that has not been verified.
We re-check every fact on a 90-day cycle and log what changes on the updates page. For the Boulder County ADU code rewrite we check the docket weekly until it is adopted.
Coverage
What we cover.
Boulder County only, and within it two jurisdictions to start:
- City of Boulder — Settled and permissive. ADUs are allowed by right in most zones, with a building permit and no separate approval step.
- 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.
We picked these two because they sit at opposite moments. The city’s rules have been settled and permissive since 2025. The unincorporated county is restrictive today, sits outside the state ADU law, and is rewriting its rules this fall.
Live somewhere else in Boulder County? You can still subscribe. We record which city you are in, and that is how we decide where to add coverage next.
We take no position on the county rewrite. We describe the process, link the documents and explain how to comment. What the rules should say is not our call to make in public.
Contact
Found something wrong?
Tell us. If a rule on this site is out of date or wrong, that is a bug and we want to fix it. Email [CONTACT EMAIL] with the page and what you found.
This site is not legal advice and it is not a permit determination. Only the City of Boulder and Boulder County can tell you what is allowed on your property.
Get ADU rule updates
We email when a rule changes in the City of Boulder or unincorporated Boulder County, with the source. Nothing else.