A basement bedroom needs a second way out. In most basements that's a window big enough to climb out of. Wisconsin's Uniform Dwelling Code sets the sizes in SPS 321.03. Put your measurements in the checker, or read the rules underneath.
When a basement needs an egress window
- Every basement needs one exit: a door to the outside or a stair to the floor above. (SPS 321.03(5)(a))
- A basement used for sleeping needs two, as far apart as practical and not reached from the same stair. (SPS 321.03(5)(b))
- The second exit can be an outside door, a stair to the floor above, a stair to a garage with a regular (not overhead) door, or an egress window in each bedroom.
- Windows count per bedroom. One egress window in the family room doesn't cover a bedroom down the hall.
- Basement bedrooms also need daylight: glass equal to at least 8% of the floor area. Other basement rooms don't. (SPS 321.05(1))
The code never defines "bedroom." If a room has a closet and a door and could be slept in, plan on an egress window, or ask the inspector before you frame it. In Madison, a house with sprinklers throughout doesn't need the second exit (MGO 29.25).
The window
| Rule | What the code says |
|---|---|
| Opening size | Net clear opening at least 20 by 24 inches, either dimension can be the height. Stops, stools, meeting rails and crank arms can't cut into it; a storm window can. There's no square-foot minimum. (SPS 321.03(6)(b)–(c)) |
| Opening it | Opens from inside without tools and without taking a sash out. Storms and screens too. (SPS 321.03(6)(a)) |
| Height | Bottom of the clear opening no more than 60 inches above the floor. Over 46 inches, a permanent step at least 20 inches wide and 9 inches deep, its top no more than 24 inches off the floor and no more than 46 inches below the opening, rated for 200 pounds. (SPS 321.03(6)(d)) |
Casements give the most clear opening for their size, because the whole sash swings out of the way. A sliding or double-hung window has to be much bigger to clear 20 by 24, since half of it never opens.
The window well
- Needed when any part of the clear opening is below the ground outside.
- At least as wide as the window, and at least 36 inches out from the wall.
- Deeper than 46 inches, it needs a permanent ladder or steps: rungs at least 12 inches wide, 3 inches out from the wall, no more than 12 inches apart, reaching to within 12 inches of the ground outside. The ladder may stick into the 36 inches by up to 6.
- It has to keep water that gets into it out of the house, which in practice means a drain or gravel to drain tile.
- Under a deck or porch, there has to be a clear path at least 36 by 36 inches and no more than 15 feet long to open yard.
Source: SPS 321.03(6)(e)–(f)
Older houses
The Uniform Dwelling Code covers houses started after June 1, 1980. Towns can extend it to work on older houses, and Madison, Middleton, Fitchburg, Verona, Sun Prairie, McFarland and Shorewood Hills all do: their codes apply it to alterations no matter when the house was built. We couldn't read Monona's and Maple Bluff's building codes online, so ask their inspectors. In practice, plan on these rules for any basement bedroom.
Permits for a new or larger opening
Cutting the foundation is a structural change, so every town we checked requires a building permit for it.
- Madison: Adding, removing or resizing a window or other exterior opening needs a building permit with plan review. It cannot go through the simple online repair/replace process.
- Middleton: Cutting a new or larger opening is a structural alteration, which is never covered by the non-structural repair exemption, so it needs a building permit. Egress openings are checked at the framing inspection. Zoning lets egress windows project into required yards within Article IV limits.
- Fitchburg: Cutting a new or larger opening is a structural alteration and window installation is listed permit work; apply under 'Alterations and Repairs to Existing Buildings'.
- Monona: Cutting a new or larger window opening changes the exterior and the structure, and Monona requires a building permit for any change to the exterior and any alteration. Even plain window replacement needs a permit.
- Shorewood Hills: A new or enlarged opening is structural work, which the handout and code both say needs a building permit.
- Sun Prairie: New or enlarged window openings count as window 'additions' and exterior changes, so they need a building permit. The city has no egress-specific handout. Basement egress windows in a finished basement fall under the basement-finish permit, which requires a plan.
- Verona: Cutting a new or enlarged opening alters the building, so it needs a building permit; the code's alteration rules call out changes to walls, light and ventilation.
- McFarland: Cutting a new or larger window opening is an exterior and structural change. McFarland requires a permit for any addition or change to the exterior, and for all alterations to any part of an existing building.
- Maple Bluff: A new or enlarged window opening is a 'Window Modification', which the Village says requires Building Board or administrative approval before a building permit is issued.
Frequently asked questions
How big does an egress window have to be in Wisconsin?
The clear opening has to be at least 20 inches by 24 inches, either way up, measured with the sash fully open. The bottom of the opening can be no more than 60 inches above the floor, and over 46 inches it needs a permanent step under it (SPS 321.03(6)).
Does Wisconsin require 5.7 square feet for an egress window?
No. Many window catalogs quote 5.7 square feet, which comes from the national model code. Wisconsin's Uniform Dwelling Code sets no square-foot minimum, only the 20 by 24 inch opening.
Does every finished basement need an egress window?
No. A basement needs a second exit only if someone sleeps down there. Even then, the second exit can be an outside door or a second stair instead of a window. If windows are the second exit, each bedroom needs its own.
How deep can a window well be before it needs a ladder?
46 inches. A deeper well needs a permanent ladder or steps, with rungs at least 12 inches wide, 3 inches out from the wall and no more than 12 inches apart.
Do I need a permit to add an egress window?
Yes, in every town on our permit guide. Cutting a new or larger opening in the foundation is a structural change. In Madison it goes through plan review rather than the quick online permit.
How we put one in
An egress window is a dig, a cut through the foundation, a header over the opening, the window, the well and its drainage. We include it in a basement finish when a bedroom needs one, and pull the permit for the opening.