The Windy City Guide to Legal Basement Egress Windows

If you plan to use part of your basement as a bedroom, or to finish it as living space, the first question is the escape route. Here is how egress windows work in Chicago-area homes, what the code asks for, and what installing one involves.

What the code asks for

Chicago and most suburbs base their residential rules on the International Residential Code (IRC), section R310, which covers emergency escape and rescue openings. Local amendments can differ, so we confirm the requirements with the building department for your address before any work starts. The IRC asks for the following in a basement bedroom:

Item	IRC minimum
Net clear opening	5.7 sq ft (5.0 sq ft for a window at grade level)
Clear opening height	24 inches
Clear opening width	20 inches
Sill height	No more than 44 inches above the finished floor
Window well	At least 9 sq ft, with at least 36 inches of projection and width
Well deeper than 44 inches	Permanently attached ladder or steps
Operation	Opens from the inside without keys, tools or special effort

The size figures work together. A 20 by 24 inch opening is only 3.3 square feet, so the window has to be larger than the minimum width and height to reach 5.7 square feet of clear opening. The clear opening is measured with the window open, not by the frame.

When you need one

A basement that only holds the furnace and storage can keep its small utility windows. Once the space becomes habitable, the rules change. Every sleeping room needs its own escape opening, even if another room down the hall already has one. Other finished rooms, such as an office or a play area, are usually covered by the same rule, depending on the local code.

Many older Chicago houses and bungalows have small, fixed or painted-shut basement windows. They are not an escape route, so a basement project often starts with enlarging one of these openings. If you are planning the whole space, see our basement remodeling page.

Choosing the window

A casement window, hinged at the side, opens fully and gives the most clear opening for its size. A slider only opens half of the frame, so it needs a wider opening in the foundation to reach the same clear area. For that reason casement and side-hinged windows are common in basements. Frames that do not rust or rot, and insulated glass, suit a window that sits below grade.

The window well and drainage

The well is part of the escape route. It needs the clear floor area from the table above, and a ladder or steps if it is deep. The IRC also limits how far the ladder may project into the well and sets the rung spacing, so the ladder does not block the exit.

Chicago-area soil holds water, and a well is a place where rain collects against the foundation. A gravel base and a drain connected to the perimeter drainage or a sump keep water away from the window. A cover keeps debris out, as long as it opens easily from the inside.

How the installation works

This is structural work on the foundation, not a window swap. In outline:

1. Permit, if your municipality requires one, and utility marking (call 811) before digging.
2. Excavation outside the wall, then cutting the opening in the foundation, with a header where the wall needs support.
3. Framing and sealing the opening, then setting and leveling the window.
4. Installing the well and its drainage, backfilling and grading the soil away from the house.

Questions we get

Can an existing basement window be enlarged?

Usually yes. The opening is cut down and sometimes wider, and the well is built outside. What is possible depends on the wall, the position of the opening and what is outside it, so we look at it on site.

What should I check once it is in?

• Clear leaves and debris from the well.
• Make sure the gravel and the drain are not blocked by silt.
• Check the seals around the frame once a year.
• Open the window now and then to be sure it moves freely.

Plan it with the rest of the basement

An egress window affects the layout, the plumbing and the electrical plan, so it is best decided at the start of a home remodeling project. We come to your Chicago home, look at the basement and give a fixed written quote after the visit. Call (773) 968-3606 for a free estimate.