Basement Egress Windows in Denver: Code, Permits & What to Expect

If you want a bedroom in your basement, you will almost certainly need an egress window. It is the single most common legal question in a Denver-area basement remodel, and it shapes the layout, the schedule and the permit. Here is what egress means, what the rules require, and what installing one involves.

What is an egress window?

An egress window is an emergency escape and rescue opening: a window big enough for a person to climb out of in a fire, and for a firefighter wearing gear to climb in. Most Denver-metro cities, including Denver, Westminster, Arvada, Thornton and Broomfield, base their residential rules on the International Residential Code (IRC), with local amendments. Always confirm the current version with your city's building department.

When do you need a basement egress window?

• Every sleeping room in the basement needs its own emergency escape opening.
• A basement with habitable space (for example a family room) generally needs at least one escape opening even without a bedroom.
• Offices, gyms and media rooms are not sleeping rooms, but if a room could be used as a bedroom later, adding egress now keeps it legal and adds resale value.

How big does an egress window have to be?

Under the IRC, the escape opening in a basement must meet all of these at once:

• A minimum net clear opening of 5.7 square feet (the actual open area when the window is fully open, not the glass size).
• A clear opening at least 24 inches high and 20 inches wide.
• A sill no more than 44 inches above the floor.
• It must open from the inside without keys, tools or special knowledge.

Casement and large sliding windows usually reach the clear-opening size most easily. A standard single-hung window often needs a bigger rough opening to qualify.

What about the window well?

Because a basement window sits below grade, it needs a well outside. The IRC calls for a well with at least 9 square feet of floor area and at least 36 inches of projection out from the wall. If the well is deeper than 44 inches, it needs a permanent ladder or steps. Many homeowners add a cover that keeps out snow and leaves but can still be opened from below.

Do you need a permit for an egress window?

Yes. Cutting or enlarging an opening in a foundation wall is structural work, and it is usually permitted either on its own or as part of the basement finish permit. The inspector checks the header over the opening, the window size and the well. A permitted egress window is also what lets you list a basement room as a bedroom when you sell.

What does installing one involve?

1. Locate the opening away from utilities, and where the outside grade allows a well.
2. Excavate outside for the well, protecting landscaping, sprinkler lines and the foundation drain.
3. Cut the foundation with a concrete saw and install a header if the opening is widened.
4. Set the window, flash and seal it, and tie the well into drainage.
5. Finish inside with trim, insulation and drywall returns.

On Denver's expansive clay soils, drainage at the bottom of the well matters as much as the window itself. A well that holds water will eventually leak.

Planning a basement bedroom?

Egress is easiest to get right when it is planned with the whole layout. Mile High Remodel handles egress windows as part of basement finishing across Denver, Westminster, Arvada, Thornton and Broomfield. See our basement remodeling in Denver, or book a free consultation.

Frequently asked questions

Can an existing basement window count as egress?

Only if it meets every size and height requirement. Most older basement windows are too small, so the opening has to be enlarged.

Can a door count instead of a window?

Yes. An exterior door or a walkout to grade can serve as the escape opening, which is why walkout basements rarely need egress windows.

Does every basement bedroom need its own window?

Yes. Each sleeping room needs its own escape opening; a hallway window does not cover the bedrooms off it.

Will an egress window make my basement brighter?

Noticeably. A full-size egress window brings in far more daylight than a small hopper window, which is one reason many homeowners add one even where it is not required.

More guides: Finishing a Basement in Colorado: 8 Things to Check First · Basement Finishing in Broomfield, CO: Permits, Egress and Design