Menu Close

Egress Window Size Requirements | Code Requirements Easily Explained with Illustrations

Found this helpful? Share it!

What is an Egress Window?

Have you ever applied for a window permit to change out your old outdated windows with new energy efficient windows for your home only to find out that some of the windows don’t meet the window egress requirements?

This is a very common problem. Building codes change over time and what was once acceptable might not be under current code when an alteration occurs. Please note that these requirements can be specific from city, county, or state therefore it is best to contact your local authority having jurisdiction to see what these requirements are.

As for a general understanding of these requirements, let us look at the 2015 International Residential Code (IRC) for what the minimum standards are.

A lot of people will refer to the term “Egress Windows” when in reality the code references “Emergency Escape and Rescue Opening”. These requirements can be found in Section R310 of the IRC. Basically the intent is to provide a means of escape and access for rescue in the event of an emergency, for example a fire.

These means of escape and access can be achieved by an operable exterior window, door, or similar device that meet the minimum size and dimensions of Section R310.

Where are Emergency Escape and Rescue Openings Required? (R310.1)

The code requires every basement, habitable attic, and every sleeping room to have at least one operable emergency escape and rescue opening. If a room is used as such, it must provide a means of escape.

Also note that if basements have multiple sleeping rooms, each sleeping room is individually required to provide a means of escape and rescue. These openings must open directly to the outside such as a public way or yard and need to be operational from the inside of the room without much effort.

What is the Minimum Size Required for Emergency Escape and Rescue Openings? (R310.2)

Egress window size and dimensions

First lets look at the minimum opening area required. This includes compliance with all of the following: the net clear opening area, net clear height opening, and net clear width opening.

  • Minimum 5.7 square feet of net clear opening area.
    • Exception: 5.0 square feet allowed if located at grade floor or below grade.
  • Minimum 24 inches of net clear height opening.
  • Minimum 20 inches of net clear width opening.

Here is a visual look at these dimensions and how they apply to the different types of windows:

Casement Egress Window

Illustration: © Building Code Trainer, 2019

Single/Double Hung Egress Window

Illustration: © Building Code Trainer, 2019

Horizontal Slider Egress Window

Illustration: © Building Code Trainer, 2019

Also note that if a window is being used to meet the egress requirements, in addition to the above, the sill height of the window shall not be more than 44 inches above the finished floor.

When a door is being used to meet the egress requirements, it must be either a side-hinged door or a slider. It must meet the minimum opening area requirements stated above. If the door is located below the adjacent ground elevation, it must provide a bulkhead enclosure with a minimum headroom height equal to the door when it is in the fully opened position.

Egress Window Well Code Requirements (R310.2.3)

When the sill height of an egress window is located below grade (common for egress windows provided for a basement) a window well must be provided.

Window Well Size

The area of a window well shall not be less than 9 square feet with a horizontal length/width of no less than 36 inches. This is to ensure that there will be a sufficient amount of space to allow occupants to escape or for fire fighters to enter.

Illustration: © Building Code Trainer, 2019

If the depth of the window well is greater than 44 inches, a ladder or steps are to be provided and permanently fixed to provide access and by no means are allowed to encroach within the required window well dimensions by more than 6 inches.

Illustration: © Building Code Trainer, 2019

The inside width dimension of ladders or rungs (a horizontal support on a ladder for a person’s foot) shall not be less than 12 inches and must project no less than 3 inches from the wall. The vertical spacing shall not be more than 18 inches on center throughout the entire height of the window well. Although the design of the steps are not mentioned within the code provisions, the design of the ladder is.

Emergency Escape and Rescue Openings in Summary

So this basically sums up the basic code requirements for egress windows and their dimensions. Therefore let us recap on the residential emergency escape and rescue opening requirements:

  1. Minimum 5.7 square feet of net clear opening area.
    • Exception: 5.0 square feet allowed if located at grade floor or below grade.
  2. Minimum 24 inches of net clear height opening.
  3. Minimum 20 inches of net clear width opening.
  4. Maximum 44 inches to window sill measured from finished floor.
  5. Window wells serving an egress window shall not be less than 9 square feet in area with a horizontal length/width of no less than 36 inches.
  6. Window wells greater than 44 inches in depth requires a permanently fixed ladder or steps to provide access.
  7. Permanent ladder or steps cannot encroach the required window well dimensions by more than 6 inches.
  8. The inside width of a ladder serving a window well shall not be less than 12 inches and must project no less than 3 inches from the wall.
  9. Vertical spacing of the rungs shall not be more than 18 inches on center.

For more information, see Section R310 of the 2015 International Residential Code for a more in-depth look at emergency escape and rescue openings.

Reference Source – 2015 International Residential Code – [Buy on Amazon]

Found this helpful? Share it!