Wisconsin Egress Window Code: Sizes, Wells, and Permits

The Wisconsin egress window code, set out in SPS 321.03(6) of the state’s Uniform Dwelling Code, requires every bedroom to have a window that provides a net clear opening of at least 20 by 24 inches, sits no more than 46 inches above the floor without a platform, opens from the inside without tools, and, when it falls below grade, is served by a window well at least as wide as the window and 36 inches deep.¹ Those are the numbers an inspector will measure. The rest of this article walks through what each one means in practice.

Minimum Opening Size

The clear opening must be at least 20 inches by 24 inches, and it doesn’t matter which dimension is the height and which is the width.¹ “Net clear opening” is the actual space a person can crawl through when the window is fully open. Not the glass size. Not the frame size. Not the rough opening in the wall. Stops, stools, meeting rails, and operator arms all count against it.

Manufacturer spec sheets often list nominal numbers that look fine on paper and fall short once the hardware is in place. Measure the real opening with the sash fully extended before you commit to a unit.

One narrow exception: a storm window is allowed to intrude on the required 20-by-24 dimensions, even though no other component can.¹ The primary window still has to meet the full opening size on its own.

Sill Height and the Platform Rule

The lowest point of the clear opening can never be more than 60 inches above the finished floor. That’s the absolute ceiling. The number that controls most installations, though, is 46 inches: once the opening sits higher than 46 inches off the floor, you have to install a permanent platform or fixture to reach it.¹

If a platform is required, it has to be:

A flat surface at least 20 inches wide and 9 inches deep.
Positioned no more than 46 inches directly below the clear opening.
No more than 24 inches above the floor at its top.
Capable of supporting at least 200 pounds of live load.

Any stair built only to reach that platform is exempt from the standard stairway rules in SPS 321.04.¹ The simpler path, when the framing allows it, is to drop the window so the sill lands at or below 46 inches and skip the platform entirely.

Operation From Inside

The window must open from inside the room without tools and without removing the sash. No keyed latches, no wing nuts, no painted-shut frames. Screens and storm windows are allowed, but they also have to be openable from inside.¹ A screen that clips in and has to be pushed out from the exterior will fail inspection.

Casement windows often work well here because the whole sash swings outward and pushes the screen with it. Confirm the crank mechanism actually leaves a 20-by-24 opening at your rough opening size before ordering.

Window Wells for Basement Bedrooms

Any egress window whose clear opening falls below the adjacent exterior grade needs an areaway, which is the code’s term for a window well.¹ Wisconsin doesn’t use a square-footage minimum. It uses two dimensions:

Width at least equal to the width of the window itself.
Depth of at least 36 inches, measured perpendicular from the outer surface of the below-grade wall.¹

The well also has to be built so water entering it doesn’t get into the dwelling.¹ The code leaves the method open. In practice, most installations tie a well drain into the perimeter foundation drain tile or set the well on a gravel bed 8 to 12 inches deep. Skipping that step is how basements flood in spring.

Ladders in Deep Wells

If the bottom of the areaway sits more than 46 inches below the adjacent grade or the top of the well enclosure, a permanent ladder or stairway is required.² The ladder has to meet specific numbers:

Rungs at least 12 inches wide on the inside.
Rungs projecting at least 3 inches from the wall behind them.
No more than 12 inches of vertical rise between rungs.
Top rung within 12 inches of exterior grade.
Each rung capable of holding a 200-pound concentrated load.¹

The ladder or stair is allowed to intrude up to 6 inches into the required areaway floor area, so you don’t need to oversize the well to fit the rungs.¹ A stair built for this purpose is also exempt from SPS 321.04’s standard stairway rules.

Decks and Porches Overhead

If the egress window discharges beneath a deck or porch, the code adds a path-of-travel requirement. The clear path has to be at least 36 inches high, at least 36 inches wide, and no more than 15 feet long before reaching a yard or open space.¹ A new low deck added over an existing basement egress window can quietly make that window noncompliant if the crawl to open air gets too long or the clearance drops.

Which Rooms Need an Egress Window

Every bedroom in a Wisconsin dwelling has to have an egress window that complies with SPS 321.03(6).³ That covers new construction and any renovation that creates a new sleeping room, including finishing a basement into a bedroom. If a basement already has a small window, that window still has to meet the 20-by-24 minimum and every other requirement in this section before an inspector will sign off on the room as a bedroom.

About the “grandfathered” claim some homeowners hear: SPS 321.03(6) does not contain a grandfathering provision for undersized egress windows. SPS 321.03(6)(b) carries the same 20-by-24 dimensional requirement that applies to the rest of the subsection. If a contractor or seller tells you an older window is grandfathered, confirm that with your local building inspector before relying on it.

Permits and Penalties

Installing or replacing an egress window generally requires a building permit. Municipalities and authorized inspection agencies review the application against the Uniform Dwelling Code, and if the plans don’t substantially conform, the permit is denied.⁴

Violations of the Uniform Dwelling Code carry forfeitures of $25 to $500 per violation, and each day the violation continues after notice counts as a separate offense.⁵ The bigger practical cost usually shows up at resale, when a buyer’s inspector flags the window and a lender holds up closing until it’s corrected. Building to the code the first time is almost always cheaper than retrofitting later.

1
Wisconsin State Legislature. Wisconsin Administrative Code SPS 321.03
2
UpCodes. Wisconsin Uniform Dwelling Code Chapter SPS 321 Construction Standards – Section: Windows Used for Exiting
3
Wisconsin State Legislature. Wisconsin Administrative Code SPS 321.03
4
UpCodes. Wisconsin Uniform Dwelling Code SPS 320 – Administration and Enforcement – Section: Disapproval of Plans and Denial of Permits
5
Wisconsin State Legislature. Wisconsin Statutes 101.66(3)