Egress Window Code Guide: Denver Metro
Last updated
Under IRC 2021 R310, an egress opening needs at least 5.7 sq ft net clear (5 sq ft at grade floor), 24 in high, 20 in wide, with a sill no higher than 44 in, and Denver requires a permit for new egress windows.
Informational only, not legal or engineering advice. Codes and local amendments change; always confirm with your building department.
IRC 2021 Section R310 (Emergency Escape and Rescue Openings)
Source: ICC IRC 2021 Ch. 3. Requirements as restated by Arapahoe County:
- Required for basements, habitable attics and every sleeping room; where a basement has sleeping rooms, each sleeping room needs one (2021 IRC R310.1). Existing-building alterations have exceptions, so ask your building department.
- Net clear opening of at least 5.7 sq ft (5 sq ft for grade-floor/below-grade openings).
- Clear opening at least 24 in high and 20 in wide.
- Sill no higher than 44 in above the floor.
- Window well: at least 9 sq ft net clear, minimum dimension 36 in, and the window must be able to open fully.
- Ladder or steps required when the well is deeper than 44 in. They may encroach no more than 6 in into the required well dimensions. Rungs need an inside width of at least 12 in, project at least 3 in from the wall, and be spaced no more than 18 in on center vertically for the full height of the well (2021 IRC R310.4.2; restated in Scott County, MN's EERO handout).
- Bars, grilles, covers and screens over an egress opening or its well must keep the required clear opening and be releasable or removable from the inside without a key, tool, special knowledge or more force than it takes to open the window normally (2021 IRC R310.4.4; restated in Scott County, MN's EERO handout). Local amendments can differ.
Denver (City & County)
- Permit required: "New window, egress window, and skylight installations require permits" (Denver CPD). Apply in e-permits as a "Building Log". Upload a scaled site plan, floor plan and elevations.
- Historic districts and landmarks need a Landmark Certificate of Appropriateness first (Denver Landmark egress review).
Jefferson County (unincorporated)
- Egress windows are listed among renovations that require a Building Permit (Jeffco).
- Window enlargements can skip Planning & Zoning and use same-day counter review by appointment (Mon–Thu) (Jeffco checklist). Building Safety plan review normally takes about 3–6 weeks.
- Fees: use the county Building Safety Fee Estimator; unincorporated Jefferson County does not charge use tax (Jeffco Fees). The county now builds to the 2024 IRC (R319) (EERO page).
Arapahoe County (unincorporated)
- Apply online through the Customer Access portal and submit PDFs only. Basements require an egress window or door per 2021 IRC R310 (guide).
- A site plan is required when the work adds a window well. See also the county page.
Related guides
- Egress window check: see if your window and well likely meet the minimums
Frequently asked questions
Where is an egress window required?
In basements, habitable attics and every sleeping room; where a basement has sleeping rooms, each sleeping room needs one (2021 IRC R310.1). Existing-building alterations have exceptions, so ask your building department.
How big does an egress window need to be?
A net clear opening of at least 5.7 sq ft (5 sq ft for grade-floor/below-grade openings), at least 24 in high and 20 in wide, with the sill no higher than 44 in above the floor.
How big does the window well need to be?
At least 9 sq ft net clear, with a minimum dimension of 36 in, and the window must be able to open fully. A ladder or steps are required when the well is deeper than 44 in.
What are the ladder rules for a deep well?
Rungs need an inside width of at least 12 in, project at least 3 in from the wall, and be spaced no more than 18 in on center vertically for the full height of the well. They may encroach no more than 6 in into the required well dimensions.
Can I put bars or a cover over an egress well?
Yes, if they keep the required clear opening and are releasable or removable from the inside without a key, tool, special knowledge or more force than it takes to open the window normally (2021 IRC R310.4.4). Local amendments can differ.
Do I need a permit for an egress window in Denver?
Yes: "New window, egress window, and skylight installations require permits" (Denver CPD). Historic districts and landmarks need a Landmark Certificate of Appropriateness first.