In Minnesota, a basement bedroom needs its own egress window with at least 5 square feet of clear opening, 24 inches high by 20 inches wide, a sill no higher than 44 inches and a 9-square-foot well. Wisconsin asks for a 20-by-24-inch opening and a sill up to 60 inches, and a sleeping basement needs two exits.
Egress window sizes in Minnesota and Wisconsin
Minnesota. The state building code is built on the 2018 International Residential Code (Minn. R. 1309.0010), with Minnesota's own changes to Section R310, the egress section. Those changes matter for basements: an emergency escape and rescue opening is required in every sleeping room, but not when an existing basement is simply altered or repaired. Build a new bedroom in that existing basement, though, and the bedroom has to comply, unless the whole basement is protected by a code-compliant sprinkler system (Minn. R. 1309.0310).
The numbers, as the City of Saint Paul's handout on the 2020 Minnesota Residential Code lays them out: a below-grade opening needs at least 5 square feet of net clear opening, at least 24 inches of clear height and 20 inches of clear width, reached by opening the window normally, and a sill no more than 44 inches above the floor (City of Saint Paul). The trap is that the minimums don't add up: 24 by 20 inches is only about 3.3 square feet. A window has to clear the height, the width and the area.
Wisconsin. The Uniform Dwelling Code measures it differently. An exit window must open from inside without tools or removing a sash, with a net clear opening of at least 20 by 24 inches in either orientation. The sill can be as high as 60 inches, but once it's higher than 46 inches, a permanent platform at least 20 inches wide and 9 inches deep goes under it (SPS 321.03(6)).
The bigger difference is the count: a basement used for sleeping needs at least two exits, as far apart as practical and not reached from the same stair. An egress window in each bedroom can serve as the second exit (SPS 321.03(5)).
| Rule | Minnesota (Duluth, Hermantown, Cloquet) | Wisconsin (Superior and area) |
|---|---|---|
| When an opening is required | Every basement sleeping room, one in each; not for other basement alterations or repairs | A basement used for sleeping needs 2 exits; an egress window in each bedroom can be the second |
| Net clear opening | 5 sq ft for a below-grade opening (5.7 sq ft above grade) | At least 20 by 24 in, either way up; no separate area figure |
| Smallest height and width | 24 in high and 20 in wide, and the area still has to reach 5 sq ft | 20 in one way, 24 in the other |
| Highest sill | 44 in above the floor | 60 in, with a fixed platform once the sill passes 46 in |
| Window well | 9 sq ft, at least 36 in wide and 36 in out, and room to open the window fully | At least as wide as the window and 36 in out from the wall |
| Ladder or steps | When the well is deeper than 44 in | When the areaway bottom is more than 46 in below grade |
| Replacing an old window | Exempt from size and sill rules if it's the maker's largest standard size that fits and opens the same or wider | Ask the building inspector which standard applies |
The window type decides how much glass you have to buy. A casement opens its full sash, while a slider or double-hung opens only half, so a casement meets the clear-opening rule in a smaller rough opening. In an old Duluth foundation, every inch of opening is cut through stone, block or concrete.
Window wells, ladders and drainage
A below-grade egress window is only as good as the well outside it. In Minnesota the well needs a horizontal area of at least 9 square feet, at least 36 inches of width and 36 inches of projection from the wall, and room for the window to open all the way.
Deeper than 44 inches, it needs a permanently attached ladder or steps usable with the window fully open, and it may take up to 6 inches of the required well size. The well also has to drain, either to the house's foundation drainage or by an approved alternative, unless the house sits on well-drained sandy or gravelly soil (City of Saint Paul).
Wisconsin calls the well an areaway: at least as wide as the window and 36 inches out from the wall, with a ladder or stair once its bottom is more than 46 inches below grade (SPS 321.03(6)). On Superior's clay, plan the drainage hardest: a well that holds water keeps it against the window.
Minnesota's code wants an opening under a deck or porch to open fully, with a path at least 36 inches high out to the yard (City of Saint Paul). Before choosing the bedroom wall, check where the well would land: clear of the driveway, the deck posts, the gas meter and the property line, and not on the uphill side of a hillside lot where it collects every spring's runoff.
Duluth's bedroom permit list and window well form
Duluth handles a basement finish under its attic rules and spells out what adding a bedroom takes: a building permit, a new smoke or CO alarm, a code-compliant egress window and, where wiring is involved, an electrical permit. When you apply, the city wants documentation from the window supplier that the unit meets egress and energy code. The city's Window Well Form may be needed for a compliant egress window, and any new well needs a site plan (City of Duluth).
Superior requires building permits for alterations; call building inspection at (715) 395-7288 about a new bedroom opening. Hermantown, Cloquet and the townships each run their own counters, listed on our building permit offices page.
Cutting a new opening in a foundation wall is structural work. Digging the well, cutting the concrete or stone and setting a header or lintel over the opening are specialist jobs, and we coordinate that crew and the window supplier. For an egress opening, we check what your address needs, and who the office requires to pull the permit, before we quote. Then we handle our part: framing the bedroom, insulating and finishing the window return, trim, drywall and paint. New outlets, lights and the alarm circuit are done by a licensed electrician under an electrical permit. Moisture tests and wall details are in our basement finishing checklist.
Septic homes: a compliance inspection comes first
Outside the sewered cities, a bedroom is a septic question before it's a carpentry one. Minnesota's septic rules require a compliance inspection before a permit is issued for adding a bedroom on property served by a septic system, wherever the local government issues bedroom permits, unless a narrow exception in the rules applies. The inspection is done by a qualified employee or licensed inspection business independent of both the owner and the installer (Minn. R. 7082.0700).
In rural Carlton County, around Mahtowa, the county wants a current septic Certificate of Compliance before it issues a zoning permit to add bedrooms (Carlton County). In county-zoned St. Louis County townships, no county inspector reviews the finish, because the county doesn't administer the State Building Code (St. Louis County). The egress window, alarms and headroom still decide whether a room is safe to sleep in, so we build to the same rules there.
If the inspection finds a failing system, that repair comes before the bedroom.
How big does a basement egress window have to be in Minnesota?
At least 5 square feet of net clear opening for a below-grade window, with at least 24 inches of clear height and 20 inches of clear width, and a sill no more than 44 inches above the floor. Those minimums don't reach 5 square feet on their own, so check all three against the maker's egress data.
Duluth asks for that supplier documentation with a new bedroom permit.
Does a basement bedroom in Wisconsin need two exits?
The basement does. Wisconsin's Uniform Dwelling Code requires at least two exits from a basement used for sleeping, placed as far apart as practical and not reached from the same stair.
The usual answer is the basement stairway plus an egress window in each bedroom: at least 20 by 24 inches of clear opening, with a sill no higher than 60 inches and a platform once it passes 46 inches.
Does an egress window well need a ladder?
Only when it's deep. In Minnesota, a well deeper than 44 inches needs a permanently attached ladder or steps usable with the window fully open; in Wisconsin, an areaway whose bottom is more than 46 inches below grade needs a ladder or stair.
Both states call for rungs at least 12 inches wide inside that stand 3 inches off the wall, and Minnesota spaces them no more than 18 inches apart.
Do I need a septic inspection to add a bedroom in Minnesota?
On a septic system, usually yes. Minnesota's rules call for a compliance inspection before a permit is issued for adding a bedroom, wherever the local government issues those permits, unless a narrow exception applies. The inspector has to be independent of the owner and the installer.
Carlton County, for example, wants a current Certificate of Compliance before it issues a zoning permit to add bedrooms.
Planning a basement bedroom? Send photos of the wall you have in mind, from inside and out, through our contact page, or call or text (715) 919-7956. You'll get a flat written quote, approved before work starts, that shows which parts we build and which specialists we coordinate. Our basement finishing page covers the rest of the room.
Next steps. If you want help with this, start with the basement finishing page or How Much Does Finishing a Basement Cost in Duluth, MN? Based in Duluth, serving Superior.
Keep reading: Addition, Finished Basement or Move? Adding Space in Duluth and Is a Remodel Worth It in Duluth? Kitchen, Bath, Basement.