ADU basics
What counts as an accessory dwelling unit, the four forms they take, and the words you will meet in the code.
Guides
The background you need once, written for homeowners. Every number in these pages is rendered from the same sourced data as the rules hubs.
Start here
The general picture.
Colorado’s ADU laws explained
HB24-1152: who it covers, what covered jurisdictions must allow, and what they can still require.
Factory-built vs site-built
State certification, the SB25-002 rules, and the local permits a modular ADU still needs.
Paying for an ADU
The options homeowners use, in general terms, and the state programs tied to supportive-jurisdiction status.
City of Boulder
Specific to the City of Boulder.
Permitting an ADU in the City of Boulder
The permit path for a City of Boulder ADU, step by step.
What drives ADU cost in the City of Boulder
The components that make one ADU cost more than another, and the fees the city publishes.
Renting an ADU in the City of Boulder
Long-term rules, the short-term ban, licensing and SmartRegs for a City of Boulder ADU.
Unincorporated Boulder County
Specific to unincorporated Boulder County.
Wells, septic, wildfire and access
The rural constraints that apply in unincorporated Boulder County whatever the rewrite says.
Get ADU rule updates
We email when a rule changes in the City of Boulder or unincorporated Boulder County, with the source. Nothing else.