Egress Windows in Boulder, CO: City vs. Boulder County Permits
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Boulder has two permit offices: the City of Boulder for addresses inside city limits and Boulder County Building for unincorporated addresses.
Boulder has two different permit offices. Which one you use depends on whether the address is inside city limits.
Inside the City of Boulder
- The city's building permit page says "the alteration, … enlargement, … repair, removal or replacement of any building or structure is authorized by a permit". Only items on its exempt list (painting, flooring, cabinets, small drywall patches and similar) skip permits (City of Boulder).
- The city's Residential Alterations Guide covers alterations where the exterior work is limited to "replacement of existing doors and windows or installation doors and windows in new opening". That is the track for a new egress opening.
- Extra approvals may apply in floodplains, wetlands, historic districts or designated landmarks (city page above).
Unincorporated Boulder County
- Boulder County Building publishes its own egress handout (B10) based on the 2021 IRC. It requires an emergency escape opening in basements and every sleeping room, at least 5.7 sq ft (5 sq ft at grade floor), 24 in high, 20 in wide, with a sill no higher than 44 in. The well must be at least 9 sq ft and 36 in wide, with a ladder when it is deeper than 44 in (B10).
- County-specific: "Foundation wall cuts for Egress Windows require an engineer's design and/or inspection … signed, sealed, and dated by a Colorado Licensed design professional" (B10).
- The county's basement-finish handout (B03) notes that under IRC R310.7, an egress opening is required for new sleeping rooms in an existing basement, but not for other basement alterations (B03).
Boulder FAQ
- I'm finishing my basement in unincorporated Boulder County but not adding a bedroom. Do I need egress? B03 says an escape opening is required for new sleeping rooms. Other alterations of existing basements don't trigger it (B03, citing R310.7).
- Do I need an engineer to cut the foundation? In unincorporated Boulder County, yes (B10). Inside City of Boulder limits, confirm engineering requirements with City of Boulder Building Services before you cut.
Note: Boulder County is not part of the Denver-Aurora-Centennial MSA (OMB Bulletin 23-01). Denver Egress Pros serves Boulder County as an adjacent market.
Permit fees
Fees and taxes are set by the jurisdiction; see the official 2026 Schedule of Fees and B33 Permit Fees for current amounts.
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Frequently asked questions
Who issues egress window permits in Boulder?
It depends on whether the address is inside city limits. The City of Boulder permits work inside the city; Boulder County Building permits unincorporated Boulder County.
What size egress opening does Boulder County require?
Boulder County's B10 handout (2021 IRC) requires at least 5.7 sq ft (5 sq ft at grade floor), 24 in high and 20 in wide, with a sill no higher than 44 in. The well must be at least 9 sq ft and 36 in wide, with a ladder when it is deeper than 44 in.
Do I need an engineer to cut the foundation?
In unincorporated Boulder County, yes: foundation wall cuts for egress windows require an engineer's design and/or inspection. Inside City of Boulder limits, confirm engineering requirements with City of Boulder Building Services before you cut.
I'm finishing my basement in unincorporated Boulder County but not adding a bedroom. Do I need egress?
The county's B03 handout says an escape opening is required for new sleeping rooms. Other alterations of existing basements don't trigger it (citing IRC R310.7).
How are Boulder permit fees calculated?
In the city, fees are valuation-based. In unincorporated Boulder County, there is a valuation table. Check the official fee schedule linked on this page for current amounts.