Egress Window Requirements in Bismarck-Mandan: Sizes, Window Wells and Permits

Who this is for: homeowners in Bismarck, Mandan and nearby Burleigh and Morton County towns who want to add a basement bedroom or finish a basement, and buyers checking whether a basement bedroom was built to code.

The short answer: egress minimums at a glance

An egress window (the code calls it an emergency escape and rescue opening) is required in a basement and in every sleeping room, sized so you can climb out and a firefighter in gear can climb in. In Bismarck, a basement egress window needs at least 5.7 square feet of net clear opening and a sill no higher than 44 inches above the floor, according to the City of Bismarck Building Inspections FAQ (checked October 2026). The other minimums come from Section R310 of the 2021 International Residential Code (IRC), which Bismarck has adopted with local amendments.

Egress window minimums for a Bismarck basement (2021 IRC and city FAQ, checked October 2026)

Requirement	Minimum
Net clear opening	5.7 sq ft (5 sq ft for a grade-floor opening, such as a main-floor bedroom)
Clear opening height	24 inches
Clear opening width	20 inches
Sill height	No more than 44 inches from the floor to the bottom of the clear opening
How it opens	From the inside, without keys, tools or special knowledge
Window well	At least 9 sq ft of floor area, at least 36 inches out from the wall and 36 inches wide, and big enough for the window to open fully
Ladder or steps	Required once the well is deeper than 44 inches

If you're adding a bedroom downstairs, we plan the egress window, the permit and the inspections as part of the basement finishing scope, and the written scope says who files. This is a plain-language summary, not legal advice. Codes change, so confirm with the city before anyone cuts the foundation.

Where an egress window is required

The IRC requires one in a basement and one in every sleeping room (Section R310.1). In Bismarck, that means:

• Every basement bedroom gets its own egress window.
• A finished basement with no bedroom still needs one, according to the city's FAQ. The model code is looser for existing basements remodeled without adding a bedroom (R310.7), so ask Building Inspections how your project will be treated before you design around it.
• Main-floor bedrooms need one too, but the net clear opening can be 5 square feet.

The window has to open to a street or other public way, or to a yard at least 36 inches wide that leads to one (R310.1). Under a deck or porch, it must open fully and leave a path at least 36 inches high and 36 inches wide to the yard (R310.2.4), so a low deck can rule out the best window spot.

Net clear opening: why most old basement windows don't pass

Net clear opening is the space a person can actually climb through with the window opened the normal way, not the size of the frame or the glass. The 5.7 square feet is 820.8 square inches, so at 24 inches of clear height you need about 34.2 inches of clear width, and at 20 inches of width you need about 41 inches of height. An opening that only meets 24 by 20 inches is about 3.3 square feet, well short.

So window style matters as much as size:

• Casement (hinged on the side, cranks out): most of the window opens, so it can pass in a smaller wall opening than other styles.
• Sliding: only one side moves, so you lose about half the width.
• Single- or double-hung: one sash moves up, so you lose about half the height, which is hard to fit in a basement wall.

Before you order, get the manufacturer's clear-opening dimensions for that exact size and style.

Replacing an existing egress window is treated differently. The IRC can accept the manufacturer's largest standard-size window that fits the existing frame or rough opening, in the same style or one that opens wider, even if it falls short of today's minimums (R310.5). Creating a new bedroom is a different case, and Bismarck's FAQ lists the full 5.7 square feet for basements, so ask the inspector before you plan around an existing window.

Window wells: size, ladders, drainage and covers

When the bottom of the window is below the ground outside, it needs a window well (the 2021 code calls it an area well). The rules, from the city FAQ and IRC Section R310.4:

• Size. At least 9 square feet of floor area, at least 36 inches out from the wall and 36 inches wide, with room for the window to open all the way. A ladder may stick into those dimensions by up to 6 inches.
• Ladder. A well deeper than 44 inches needs a permanently attached ladder or steps usable with the window fully open. Rungs must be at least 12 inches wide, stand at least 3 inches off the wall and be no more than 18 inches apart vertically.
• Bismarck's alternatives. The city's building code amendments (Title 4) also allow a permanently attached platform at least 30 by 16 inches, no more than 42 inches below the top of the well, or a terraced well with steps no more than 24 inches high and at least 12 inches deep.
• Drainage. The well has to drain, normally into the foundation drain system, unless the foundation sits on well-drained sand or gravel.
• Covers and grates. Allowed, but they must release or lift off from the inside without a key, a tool or more force than it takes to open the window.

A cover keeps snow out of the well, and a snow-packed well won't help anyone in a fire. Pick one the person sleeping there could push open from inside.

Sill height: 44 inches in Bismarck, and what's different in Mandan

The sill is the bottom of the clear opening. In Bismarck it can be no more than 44 inches above the floor, which usually decides how low the foundation cut goes.

Mandan doesn't publish its own egress rules. Its building code page says the city has adopted the North Dakota State Building Code in its most current edition. According to the North Dakota Department of Commerce, that code took effect January 1, 2026, and is based on the 2024 IRC, which keeps the same 5.7-square-foot, 24-inch and 20-inch minimums. The 2026 North Dakota State Building Code adds a state exception that lets a below-grade egress window have a sill up to 48 inches, plus the same platform and terraced-well options Bismarck allows.

Bismarck writes its own amendments and its FAQ still lists 44 inches, so don't carry the 48-inch exception across the river. In Mandan, confirm with Building Inspection at (701) 667-3230.

Permits and inspections

Plan on a permit. Bismarck's list of projects that require one includes renovations, remodels and basement finishes, and cutting a new opening in a foundation wall is structural work. For a stand-alone egress window, call the Building Inspections Division at (701) 355-1465 to confirm the permit type. The city says most permits other than new construction are issued within one business day. Mandan's permit page says a permit is needed to construct, enlarge, alter or repair a building.

Tell us the property address. We identify the permitting office, discuss the required inspections, and state who will file and who pays the fees in your written scope. Egress window size is worth checking against the code before the window is ordered, because a unit that is too small has to be replaced.

A permitted basement finish also triggers smoke and carbon monoxide alarms placed as the IRC requires in new homes (R314.2.2 and R315.2.2); a window on its own is exempt. For stairs, headroom and the inspection sequence, read our guide to the full basement permit and inspection process in Bismarck and Mandan.

Before anyone digs: call 811

North Dakota law requires notifying 811 at least two business days before digging, according to the North Dakota Public Service Commission. Utilities mark their own lines; private lines like sprinkler pipes or a gas line past the meter are up to whoever requested the locate. Make sure 811 has been called before anyone digs the window well. On our jobs, HHI calls 811 before digging; the owner marks private lines.

Can you put in an egress window in winter?

Yes, but winter makes the outside half of the job harder. Bismarck's code designs for a 4-foot frost depth and a winter design temperature of minus 19°F (Title 4, Table R301.2), and a basement window well goes down through that frozen layer. Whether a winter install makes sense depends on access, ground conditions and the crew schedule, and frozen ground adds digging time and cost that should show up in the estimate. We review those before setting dates.

On a winter basement finish, schedule the egress cut early so framing and drywall can be built around it, and plan for spring: the well has to drain, and the soil around it should slope away from the house.

What drives the cost of an egress window

Egress windows are one of the main reasons basement prices vary, and the price depends mostly on what's outside the wall:

• Poured concrete or block foundation
• Well depth, and whether it needs a ladder, platform or terraces
• Drainage into the foundation drain or gravel
• What's in the way: a deck, an AC unit, a gas meter, landscaping
• Framing and drywall around the new opening
• Frozen ground in winter

For a real number: a 2026 HHI estimate for one new egress opening in Bismarck carried a $7,500 preliminary allowance. It included removing the existing window, normal excavation access, cutting and enlarging the foundation opening, framing, a standard window and well, a cover, flashing, sealing, normal trim and cleanup. Foundation thickness, digging access, obstructions, groundwater, utility conflicts and drainage requirements can change that number, so the opening needs an on-site check. Keeping a serviceable existing window is a different job: in a separate water-damage repair estimate, removing and reinstalling the existing unit and replacing damaged perimeter framing was a $1,700 allowance.

Is your basement window leaking instead?

A leaking window may need drainage or frame repairs. A new bedroom escape opening is a different scope. First, tell where the water shows up: in the well, at the frame or under the sill. A new window won't fix poor drainage on its own. Does water collect in the well or first appear under the sill? Send your town and, if it is safe, one photo inside and one outside, and see our page on egress window leak repair.

Our guide to basement prices shows how an egress window fits into a basement finishing budget. And because a new opening and well change how water reaches the foundation, start with checking a basement for moisture before you finish it.

Frequently asked questions

What size does an egress window need to be in Bismarck?

For a basement, at least 5.7 square feet of net clear opening, at least 24 inches high and 20 inches wide, with a sill no higher than 44 inches above the floor. Main-floor bedrooms can have 5 square feet.

Does a basement need an egress window if there's no bedroom?

In Bismarck, yes. The city's FAQ says a finished basement with no bedrooms still needs at least one egress window, and each basement bedroom needs its own. In Mandan, ask the Building Department at (701) 667-3230; Mandan applies its own code with exceptions by location and opening type.

When does a window well need a ladder?

When it's deeper than 44 inches. The ladder or steps must be permanently attached and usable with the window fully open. Bismarck also allows a 30-by-16-inch platform within 42 inches of the top, or a terraced well.

Can I put a cover on an egress window well?

Yes, if it releases or lifts off from the inside without a key, a tool or more force than it takes to open the window, and the window still opens fully under it.

Do I need a permit to install an egress window in Bismarck?

Plan on one. Bismarck requires permits for renovations, remodels and basement finishes, and a new egress window means cutting the foundation. Call Building Inspections at (701) 355-1465 to confirm the permit type.

Planning a basement bedroom? We check the clear opening, well and installation access before pricing it, and put it in a free written estimate with the permit steps. Call or text Viktor at (701) 329-9659 with your town, photos and what you want to change. Our office follows up during business hours. HHI is licensed in North Dakota (contractor license No. 000050538, Class D), and our employees are covered through WSI.