If you are finishing a basement, adding a bedroom, or replacing a window in one, this is the requirement that decides whether the room is legal. The numbers are specific and they are not negotiable.
Every sleeping room, basement and habitable attic needs at least one emergency escape and rescue opening. The window must give a net clear opening of at least 5.7 square feet — 5 square feet at grade level — at least 24 inches high and 20 inches wide, with the sill no more than 44 inches above the floor. The opening has to be achievable by normal operation from inside, with no keys or tools.
Basements, habitable attics and every sleeping room need at least one operable emergency escape and rescue opening. Where a basement contains sleeping rooms, each of those rooms needs one, but the rest of the basement does not.
The opening has to lead somewhere real — directly to a public way, or to a yard or court that opens to one.
This is what makes a basement room legally a bedroom. A finished basement room without one is not a bedroom, whatever it is called when the house is listed.
MN DLI, quoting R310.1: “Basements, habitable attics and every sleeping room shall have not less than one operable emergency escape and rescue opening. Where basements contain one or more sleeping rooms, an emergency egress and rescue opening shall be required in each sleeping room, but not be required in adjoining areas of the basement.” Source: MN DLI, Emergency Escapes and Rescue Openings
A net clear opening of at least 5.7 square feet, at least 24 inches high and at least 20 inches wide. Grade-floor and below-grade openings get a slightly smaller allowance of 5 square feet.
The phrase that catches people is net clear. It is the hole you can actually climb through with the window operating normally — not the rough opening, not the frame size, and not what the catalogue calls the window. The sash, the frame and the hardware all come out of it.
That is why the minimum height and width alone do not get you there: 24 by 20 inches is 3.3 square feet, well under 5.7. Both the minimums and the area have to be satisfied at once, which in practice drives the window size up.
MN DLI, quoting R310.2.1: “Emergency and escape rescue openings shall have a net clear opening of not less than 5.7 square feet. The net clear opening dimensions required by this section shall be obtained by the normal operation of the emergency escape and rescue opening from the inside. The net clear height of the opening shall be not less than 24 inches and the net clear width shall be not less than 20 inches. Exception: Grade floor openings or below-grade openings shall have a net clear opening area of not less than 5 square feet.” Source: MN DLI, Emergency Escapes and Rescue Openings
No more than 44 inches above the floor. The point is that somebody has to be able to get out through it in the dark, in smoke, possibly a child — so it cannot be up near the ceiling.
If the sill is below grade, you need a window well that meets its own requirements.
MN DLI, quoting R310.2.2: “Where a window is provided as the emergency escape and rescue opening, it shall have a sill height of not more than 44 inches above the floor; where the sill height is below grade, it shall be provided with a window well.” Source: MN DLI, Emergency Escapes and Rescue Openings
The well has to be at least 9 square feet in horizontal area, with a horizontal projection and width of at least 36 inches, and it has to allow the window to open fully.
If the well is more than 44 inches deep, it needs a permanently affixed ladder or steps that can be used with the window fully open. A ladder is allowed to encroach up to 6 inches into the required dimensions of the well, which is the one piece of slack in the rule.
MN DLI, quoting R310.2.3 and R310.2.3.1: “The horizontal area of the window well shall be not less than 9 square feet, with a horizontal projection and width of not less than 36 inches. […] Window wells with a vertical depth greater than 44 inches shall be equipped with a permanently affixed ladder or steps usable with the window in the fully open position.” Source: MN DLI, Emergency Escapes and Rescue Openings
It can have a lock, but the opening has to be operable from inside the room without keys, tools or special knowledge. A window somebody has to find a key for in the dark does not satisfy the rule.
Window opening control devices — the limiters that stop a window opening far enough for a child to fall — are allowed on an egress window, but they have to comply with ASTM F2090, which means they release to the full opening when needed.
Bars, grilles and screens over an egress window have to be releasable from inside without tools or special knowledge too. A fixed security grille over a bedroom window is the version of this that kills people.
MN DLI, quoting R310.1.1: “Emergency escape and rescue openings shall be operational from the inside of the room without the use of keys, tools or special knowledge. Window opening control devices on windows serving as a required emergency escape and rescue opening shall comply with ASTM F2090.” Source: MN DLI, Emergency Escapes and Rescue Openings
A few, and they are narrow. Storm shelters and basements used only to house mechanical equipment, up to 200 square feet total, are exempt. So are basements and basement bedrooms in a building protected by an automatic sprinkler system installed to IRC P2904 or NFPA 13D.
Sprinklers are the real-world exception, and they are uncommon in existing Minnesota housing. For most people replacing a basement window, the full requirement applies.
One more thing worth knowing: replacing a window in a sleeping room is permitted work, and the replacement has to meet current code. A like-for-like swap of an undersized old window is not automatically allowed.
This page quotes Minnesota statutes and the adopted Minnesota building code and links to the official text of each so you can read it yourself. It is general information from a licensed contractor, not legal advice, and it is not a substitute for reading your own policy. Statutes and codes are amended; the linked sources are authoritative, this page is not. Last reviewed 2026-10-27.
Straight answers to the questions Minnesota homeowners ask before they call anyone.
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