Do I Need a Permit for an Egress Window?

Adding an egress window to a basement means sawing an opening through a foundation wall, digging a hole beside the house, and setting a well and window that a person must be able to climb out through in the dark. Building departments treat it as structural and life-safety work, and almost all of them require a permit for it.

This guide covers cutting a new egress opening or enlarging an existing basement window. If you are only swapping a window in its existing opening, see Do I Need a Permit to Replace Windows?. If the egress window is part of a larger basement project, read Do I Need a Permit to Finish a Basement? too.

Code citations below come from the unamended 2021 International Residential Code (IRC). Section numbers in R310 changed between editions: in the 2018 IRC, the window well rules were R310.2.3 and the replacement window allowance was R310.2.5. In the 2021 edition those became R310.4 and R310.5. Check which edition your jurisdiction has adopted before you rely on a section number.

Why a new egress opening needs a permit

IRC R105.2 lists the work that does not need a building permit: small sheds, fences up to 7 feet, low retaining walls, sidewalks, finish work like painting and flooring, small low freestanding decks, and a few other items. Cutting or enlarging an opening in a foundation wall is not on that list, so under the model code it needs a permit. Local codes add exemptions of their own, but in practice new egress openings are treated as permit work almost everywhere.

The permit covers three things a reviewer cares about:

• Structure. The foundation wall carries the house. Cutting it removes material that was holding up the rim joist and the floor above.
• Escape and rescue. The opening has to be big enough, low enough, and easy enough to open that someone can get out, and a firefighter in gear can get in.
• Water. A below-grade well is a hole against your foundation, so it has to drain.

What the 2021 IRC requires for the opening

Where it is required (R310.1). Basements, habitable attics, and every sleeping room need at least one operable emergency escape and rescue opening. If a basement has sleeping rooms, each one needs its own. The opening must lead to a public way, or to a yard or court at least 36 inches wide that opens to one. Exceptions include storm shelters, basements used only for mechanical equipment and no larger than 200 square feet, and some sprinklered homes.

Existing basements (R310.7). This is the provision people miss most often. In an existing house, the 2021 IRC requires an escape opening when you create a new sleeping room in the basement. Other basement alterations and repairs do not trigger one under the model code. Your local code may be stricter, so confirm before you assume a rec room does not need one.

Size (R310.2.1 and R310.2.2). The net clear opening must be at least 5.7 square feet. It must be at least 24 inches high and at least 20 inches wide, measured with the window opened in its normal way. Meeting both minimums is not enough on its own: a 20 by 24 inch opening is only 3.3 square feet. A 20-inch-wide opening has to be about 41 inches tall to reach 5.7 square feet.

The 5.0-square-foot exception. The 2021 IRC allows 5 square feet for a grade-floor opening, which Chapter 2 defines as one whose bottom is no more than 44 inches above or below the finished ground next to it. A typical basement window in a deep well falls outside that definition, so it needs the full 5.7. The 2018 IRC worded the exception as “grade floor or below-grade openings,” which is why older handouts may say 5.0 square feet for basements.

Sill height (R310.2.3). The bottom of the clear opening can be no more than 44 inches above the floor.

Operation (R310.1.1). The opening must work from inside without keys, tools, or special knowledge. Window opening control devices are allowed only if they comply with ASTM F2090.

Under decks and porches (R310.2.4). An opening under a deck, porch, or cantilever must open fully and have a path at least 36 inches high and 36 inches wide to a yard or court.

Window well rules

Any escape opening whose bottom is below the adjacent grade needs an area well (R310.4):

• Size (R310.4.1). At least 9 square feet of horizontal area, with at least 36 inches of projection out from the wall and 36 inches of width. The well must let the window open fully, which matters with casements: a sash that swings into a tight well can block the opening.
• Ladder or steps (R310.4.2). Required when the well is more than 44 inches deep. They must be permanently fixed and not blocked by the open window. A ladder may encroach no more than 6 inches into the required well dimensions.
• Ladder details (R310.4.2.1). Rungs at least 12 inches wide inside, projecting at least 3 inches from the wall, spaced no more than 18 inches apart for the full depth.
• Step details (R310.4.2.2). At least 12 inches wide, treads at least 5 inches deep, and risers no more than 18 inches.
• Drainage (R310.4.3). The well must connect to the foundation drainage system. The exception is a foundation on well-drained Group I soils (sand and gravel mixes).
• Covers and grates (R310.4.4). Allowed, but they must still leave the required clear opening and release from inside without a key, tool, or more force than it takes to open the window normally.

Cutting the foundation wall

The IRC’s R310 rules cover the size and function of the opening. They do not give a prescriptive detail for cutting a hole in an existing concrete or block foundation. That is why reviewers ask how you will support the wall above the cut.

Expect the department to want a framing or structural detail showing what spans the new opening, and in some places a design from an engineer. Lakewood, Colorado, for example, requires a structural engineer to evaluate site conditions and design the cut and reinforcement whenever an existing opening is altered or a new one is created. Ask about this before you schedule the saw cutting.

How the rules differ by city

All of these examples start from the IRC, but each adds its own twist.

• Lakewood, Colorado. Beyond the engineer requirement, Lakewood’s handout says temporary or fixed steps cannot be used to meet the 44-inch sill limit. It also says a casement in a well must be able to open to 90 degrees while still leaving the 36-by-36-inch well clear, and that the bottom ladder rung must be no more than 18 inches above the well floor.
• Minneapolis, Minnesota. The city’s basement egress handout (last updated 09/2024, based on the 2020 Minnesota Residential Code) requires window wells to be at least 2 feet from any side or rear lot line. It also warns that an egress window permit does not legalize a basement bedroom built without a permit or allow an extra dwelling unit. Finishing a room, adding a bedroom, or adding a unit needs separate permits.
• Fargo, North Dakota. Fargo’s handout lists local amendments that relax the model code. It allows a 48-inch sill height for below-grade escape windows instead of 44. It allows a permanent platform of at least 30 by 16 inches to bring a well’s depth to 42 inches or less, so the well doesn’t need a ladder. It also allows terraced wells with no more than a 24-inch rise and at least 12 inches of projection per level.
• Aurora, Colorado. Aurora’s 2026 flat-rate fee schedule (Form A175, revised 08/2026) lists egress window installation at $99. A basement finish is $536. The city still collects use tax and county tax based on building material costs, so the flat fee isn’t the whole bill.
• Denver, Colorado. On an individual landmark or in a historic district, an egress window also goes through Landmark Preservation design review. You apply through e-permits for a Landmark Certificate of Appropriateness, with labeled photos, elevations and sections of the window and well, and a window schedule.

Fees elsewhere are often based on valuation rather than a flat rate. Our building permit cost guide explains how those calculations usually work.

Replacing an existing window is a different question

If a window already serves as the escape opening and you are only replacing it, the 2021 IRC (R310.5) exempts the replacement from the size and sill rules. To qualify, it must be the manufacturer’s largest standard size that fits the existing frame or rough opening, and the same operating style or one with an equal or larger opening. It also can’t be part of a change of occupancy. This allowance does not apply once you enlarge the rough opening.

Even plain replacements need a permit in some cities. Saint Paul, Minnesota, requires a building permit for new or replacement windows, including storm windows. Minnesota’s code also adds stricter rules for rooms used for state-licensed foster care or day care.

What the inspections cover

Inspection sequences vary, but for a new egress window they usually include:

1. Framing or rough-in inspection after the opening is cut and framed, so the inspector can see the header or reinforcement, the opening size, and flashing before finishes cover them.
2. Final inspection, where the inspector opens the window, measures the clear opening and sill height, checks the well size, ladder, drainage, and any cover, and usually checks smoke and carbon monoxide alarms.

See building inspection stages for how to schedule and prepare for each visit.

What to have ready when you apply

• Site plan showing the house, the well location, and distances to property lines and other structures.
• Basement floor plan showing the room the window serves, existing windows, and mechanical equipment.
• Window specifications: model, rough opening, operating type, and the manufacturer’s net clear opening width, height, and area. Use clear-opening numbers, not rough-opening numbers.
• Section drawing through the opening showing finished floor to sill height, well depth, and the ladder or steps.
• Structural detail for the cut: header or lintel, and an engineer’s design if your department requires one.
• Well details: material, dimensions, cover, and how it drains.
• Contractor information, or an owner-builder declaration if you are doing the work yourself. See owner-builder permits.

Questions to ask your building department

• Which IRC edition is in effect, and are there local amendments to R310 for sill height, well depth, or platforms?
• Does cutting a foundation opening require an engineer’s design here?
• How close to a side or rear lot line can the well be?
• Is a flat fee available, or is the permit priced by valuation?
• Does my address fall in a historic district or need zoning review?
• If I am adding a basement bedroom, what other permits do I need?

If a previous owner cut an egress window without a permit, read our guide to unpermitted work for how retroactive permits usually work. To find the right office for your address, find your local building department.