An egress window is one of the few things in a window schedule that is a pass or fail test. The dimensions are published, they are measured on site, and a bedroom that misses them does not get signed off.
The requirement is also the one architects and owners most often get wrong, because the code states three size minimums and a window built to those three minimums does not pass. That sounds like a contradiction. It is not, and the reason is worth understanding before you size an opening.
What is an egress window?
The formal term is an emergency escape and rescue opening, and it is covered by Section R310 of the California Residential Code. Los Angeles County adopts the CRC through Title 26 of the County Code, and the City of Los Angeles adopts it through Chapter IX of the Municipal Code, each with local amendments. The R310 dimensions below are set at state level and carry through both.
The opening has two jobs, and the second one explains the numbers:
- Someone inside has to get out without using the interior of the building.
- A firefighter has to get in wearing a helmet, turnout coat and a self-contained breathing apparatus on their back.
That second job is why the area requirement is so much larger than the width and height requirements imply. A hole that a person can squeeze through is not necessarily a hole that someone in full gear with a tank can enter.
The four Los Angeles egress requirements
Four limits, and an opening has to satisfy all four at once:
| Requirement | What it measures | Limit |
|---|---|---|
| Net clear opening width | Narrowest horizontal dimension of the open hole | 20″ min |
| Net clear opening height | Shortest vertical dimension of the open hole | 24″ min |
| Net clear opening area | Total open area, width times height | 5.7 sq ft min |
| Sill height | Finished floor to bottom of the clear opening | 44″ max |
Net clear opening is the phrase that matters. It is the actual unobstructed hole measured with the window fully open. It is not the rough opening, not the frame size, and not the glass area. Frame, sash, stops and hardware all take away from it.
One exception worth knowing: a grade-floor or below-grade opening is allowed a reduced 5.0 square feet of net clear area. The 20 inch, 24 inch and 44 inch limits are unchanged.
Why a 20 inch by 24 inch window does not pass
This is the trap, and it catches experienced people.
Read the three size minimums quickly and it is natural to conclude that 20 inches by 24 inches is a compliant egress opening. Do the arithmetic:
| Clear opening | Area | Against 5.7 sq ft |
|---|---|---|
| 20″ × 24″ | 480 sq in = 3.33 sq ft | Fails |
| 20″ × 36″ | 720 sq in = 5.00 sq ft | Fails |
| 20″ × 42″ | 840 sq in = 5.83 sq ft | Passes |
| 28″ × 30″ | 840 sq in = 5.83 sq ft | Passes |
| 36″ × 24″ | 864 sq in = 6.00 sq ft | Passes |
5.7 square feet is 820.8 square inches. A 20 by 24 opening delivers 480. It is not close.
The width and height figures are floors that no opening may drop below, not a size that satisfies the rule on its own. The area requirement is the one that actually governs, and it forces the opening to be considerably larger than either minimum suggests. Two numbers follow from it and are worth committing to memory:
- At the minimum 20 inch width, you need about 41 inches of clear height.
- At the minimum 24 inch height, you need about 34 inches of clear width.
Anything narrower or shorter than those pairings fails on area, whatever the other dimension is doing.
How operation type decides whether you pass
Two windows with identical frame sizes can give completely different net clear openings, because what counts is how much of the frame the sash actually clears.
- Casement. The sash swings out of the opening, so nearly the full frame counts. This is the most area per unit size, and on a tight opening it is often the only type that will pass.
- Single-hung and double-hung. Only the open sash counts, so you get roughly half the frame height. A hung unit has to be about twice as tall as a casement to deliver the same area.
- Horizontal slider. Only the moving panel clears, so you get roughly half the frame width. A slider has to be much wider than a casement for the same result.
- Awning. The sash swings from the top and usually obstructs the opening. Rarely workable for egress.
- Fixed. Never qualifies. It does not open.
This is where egress becomes a product decision rather than purely a code one. If an elevation calls for a narrow opening, the operation type is usually what determines whether that opening can be a bedroom window at all.
Where egress windows are required
- Every sleeping room. If it is a bedroom, it needs one.
- Basements with habitable space. Including finished basements without a bedroom.
- Not every room. Living rooms, kitchens and dining rooms are not subject to R310.
A room with a door opening directly outside can satisfy the requirement through that door. The opening also has to discharge to a public way, yard or court, so a bedroom window opening into an enclosed interior space does not count no matter how large it is.
Bars, screens and window wells
Security bars, grilles and insect screens are permitted over an egress opening, but only if they can be released from inside without a key, a tool, or special knowledge, and without more force or effort than operating the window normally. A bar set that needs a key defeats the opening and will not pass.
Below-grade openings need a window well, and the well has its own minimums: at least 9 square feet of horizontal area with a minimum dimension of 36 inches, and a permanently affixed ladder or steps if the well is deeper than 44 inches.
Getting this resolved before it reaches plan check
Egress is the kind of requirement that is inexpensive to solve during specification and expensive to solve after approval, because the fix is almost always a larger opening, which means structure and elevation changes rather than a different window.
What we can do is tell you the net clear opening a given unit actually delivers, which is a manufacturer figure rather than something you can calculate from the nominal size, and tell you which operation type gets the area you need into the opening you have. That is the part we build with the manufacturer.
Bring floor plans and elevations with bedroom openings marked. Showrooms in Brentwood, Irvine, San Diego, and Santa Barbara, by appointment.
Egress runs alongside the energy requirement, and the two constrain each other. Our guide to knowing your windows meet Title 24 covers the U-factor and SHGC side.
Common questions
What size window is required for egress in Los Angeles?
An emergency escape and rescue opening has to satisfy four separate limits at the same time: a net clear opening width of at least 20 inches, a net clear opening height of at least 24 inches, a net clear opening area of at least 5.7 square feet, and a sill no higher than 44 inches above the finished floor. Net clear opening means the actual unobstructed hole with the window fully open, not the rough opening and not the glass size.
Can a 20 inch by 24 inch window meet egress requirements?
No. That is the single most common misreading of the code. 20 inches by 24 inches is 480 square inches, which is 3.33 square feet, well short of the 5.7 square feet the area rule requires. The width and height figures are floors that no opening may go below, not a size that passes on its own. At the minimum 20 inch width you need about 41 inches of clear height, and at the minimum 24 inch height you need about 34 inches of clear width.
How high can an egress window sill be above the floor?
No more than 44 inches, measured from the finished floor to the bottom of the net clear opening. This is why a high transom or a clerestory window cannot serve as the egress opening for a bedroom no matter how large it is.
Do all bedrooms need an egress window?
Every sleeping room needs an emergency escape and rescue opening, and so does a basement containing habitable space. A room served by a door opening directly to the outside can satisfy the requirement through that door. The opening has to discharge to a public way, yard or court, so a window opening into an enclosed space does not qualify.
Is a casement or a single-hung window better for egress?
A casement is far more efficient. Its sash swings clear of the frame, so nearly the whole opening counts toward the net clear area. A single-hung gives you roughly half the frame height and a horizontal slider roughly half the width, so both have to be substantially larger units to deliver the same 5.7 square feet. On a tight opening the casement is often the only operation type that will pass.
Dimensions above are the Section R310 requirements of the California Residential Code as adopted in Los Angeles County (Title 26) and the City of Los Angeles (Chapter IX). Code is revised on a three-year cycle and jurisdictions adopt with local amendments, so confirm the edition in force for your project with the building department having authority. This is a specification reference, not a code compliance opinion.