Basement Egress Windows: Definitions, Requirements, Costs, and Why They’re Worth Every Penny

Example of a basement egress window at the left of the photo

When homeowners plan a finished basement, the focus is usually on the fun parts — a new family room, guest space, home office, or game room. What often receives less attention is one of the most important safety features in the entire project: emergency egress.

Emergency egress, such as the basement egress window, lacks the flash of a new family room, but they certainly are critical.  Local building codes in places like St. Charles and St. Louis require them.   And for good reason: Finished basements become living spaces, and living spaces need exits.

What is an Egress Window?

Simply put, an egress window is a window large enough for a person to escape through – or for firefighters to enter in full gear – during an emergency. In essence, egress windows are designed to act as a second emergency exit – hopefully one that will never need to be used.  But such a window can make all the difference in a fire or other urgent situation.

Local Codes for Basement Egress Windows

Local codes bring specific requirements to egress windows when refinishing a basement. 

For example, the Finished Basement Requirement Guide published by the St. Charles County Department of Community Development outlines baseline criteria that emergency egress windows must meet, including:

• Opens from the inside without keys, tools, or special knowledge

• Provides a minimum clear opening of 5.0 square feet

• Has a minimum clear open window height of not less than 24”

• Has a minimum clear openable window width of not less than 20”

• Has a sill 44” or less above the finished floor

These requirements are based on the County’s adopted residential building codes and are reviewed during the permit and inspection process.

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Example requirements for emergency egress windows from the St. Charles, MO County Department of Community Development.

Why Finished Basements Trigger Egress Requirements

Legally and functionally, finishing a basement changes how that space is classified. An unfinished basement isn’t considered “habitable,” but once drywall goes up, flooring goes in, and the room becomes a usable living area, it becomes subject to the same safety rules as any other part of the home.

The 2024 International Residential Code, section 319.1, states that “every sleeping room shall have not less than one operable emergency escape and rescue opening.”

However, the distinction between a “sleeping room” and a “regular living area” can be surprisingly broad. Some municipalities interpret sleeping rooms to include bedrooms as well as spaces where people might reasonably fall asleep, such as media rooms or large family rooms. Some jurisdictions make the determination based on how the space could be used, not just how the homeowner intends to use it.

It’s easy to see the reason for a broadened use of the term sleeping room. In many homes, the basement becomes a favorite spot for the family. That means people may be resting or falling asleep in the space, which necessitates a second exit.

Requirements Change By City and County

Here’s where things can get even trickier when it comes to code requirements for basement egress windows.  Even beyond definitions of a sleeping room, egress code requirements vary by locale.  For example,

• St. Charles County: Often does not require an egress window unless the basement remodel includes a bedroom. (Note: New construction and additions always trigger egress requirements.)

• Parts of St. Louis County: May require an egress window for any finished living space, even if it is not designated as a bedroom.

• Some rural counties: May have limited inspection requirements for remodels, though new construction almost always requires review.

It can be challenging to stay on top of the “who, what, where, and when” of egress rules, as they vary from area to area. Further, codes are living documents, and requirements change.

It’s a big reason why a homeowner should work with an experienced contractor like McBride Construction.  What’s required in one zip code may not be required two miles away, even within the same county.  And code requirements evolve over time, which is why relying on past projects or assumptions can lead to costly surprises. It’s why McBride Construction always researches these and other issues prior to providing a quote.

Why You Need a Basement Egress Window Even When Not Required

Setting aside requirements for the moment, basement egress windows offer several benefits.

• Safety.  A second exit notably increases survivability in a fire or smoke event.  Circumstances can block an exit to the stairs.  The code requirements are in place because they are life-safety features designed to protect the people in your home.

  
  

• Natural light. Basements can feel dark or enclosed.  A larger window brings in daylight, brightening the atmosphere and mood.

  
  

• Ventilation.  Operable egress windows allow fresh air to circulate if needed.

  
  

• Greater flexibility.  With proper egress, a room can legally and safely serve as a bedroom, office, or guest space.

  
  

• Better resale value.  Proper egress can allow a basement room to qualify as a legal bedroom, which may increase resale value and market appeal.

  
  

• Peace of mind. Knowing there is an alternate emergency exit provides reassurance that your family and guests have a safe way out if something unexpected occurs.

Cost and Planning for an Egress Window

The cost of installing an egress window varies depending on factors such as excavation depth, soil conditions, window type, and a home’s foundation.  That said, the biggest cost-saver for egress window considerations is planning and deciding early.

Adding an egress window later can trigger plan updates, permit revisions, supplemental inspections, and changes in materials and labor costs.  Discussing egress requirements during the planning phase helps everyone know what to expect and keeps your project moving smoothly.

Final Thoughts

Whether required by code or not, egress windows are a smart investment in any basement remodel. They improve safety, expand how the space can be used, add value, and provide peace of mind.

If you’re considering finishing your basement and want to discuss your project, what your local area requires, other egress options beyond windows (like full walk-out access), or what makes sense for your specific project, McBride Construction is always happy to discuss so that you can make a confident, well-informed decision. Reach out by phone or use the our contact form to send us a message.