Every bedroom in a new Washington home needs at least one window a person can climb out of in a fire, and the residential code puts four numbers on it. The clear opening has to be at least 5.7 square feet (5.0 on a grade-floor or below-grade opening), at least 24 inches high and at least 20 inches wide, and the bottom of that opening can sit no more than 44 inches above the finished floor. Washington builds to the International Residential Code with state amendments, and these are the IRC numbers. They have been the same for years, but always confirm the current requirements with your plans examiner.
What catches builders out is how the opening gets measured.
The inspector measures the hole, not the window
Those dimensions apply to the net clear opening: the space a person actually passes through with the window opened as far as it goes, by normal operation. Rough opening, frame size and glass size do not count. A window that looks plenty big on the plans can come up short once you take away the frame, the fixed half of the unit and the sash.
The 24 by 20 minimums are not enough on their own, either. A 24 by 20 opening is only 480 square inches, and 5.7 square feet is about 821. So if the clear opening is exactly 24 inches high, it has to be at least 34.2 inches wide. If it is exactly 20 inches wide, it has to be about 41 inches high. Most egress failures are windows that pass one minimum and miss the area.
How each window type gets there
The same rough opening gives very different clear openings depending on how the window operates.
A casement is the easiest egress window. The whole sash swings out, so the clear opening is close to the full frame size, and a fairly modest unit clears 5.7 square feet. If the casement has an opening limiter, the clear opening is measured with the sash fully open, and the limiter has to release without tools or special knowledge. Ask your supplier how theirs releases before you count on it for egress.
A single hung opens only its bottom half, and the bottom sash slides up behind the top one. The clear height ends up a little under half the frame height. To get 24 inches of clear height, the frame has to be well over 48 inches tall, and the width still has to make up the area. Single hungs work for egress, but they need a tall unit.
A horizontal slider has the same problem turned sideways. One sash moves and the other stays put, so the clear width is a little under half the frame width. A slider sized for egress ends up wide and fairly short, which suits a basement bedroom or a low wall under a roofline.
A picture window does not open, so it never counts.
The sill height trap
The 44 inches is measured from the finished floor to the bottom of the clear opening, not to the bottom of the frame. On a single hung, the bottom of the opening is the top of the frame's sill. Add flooring after the windows are set, or set a tall unit high on the wall to line up with the headers, and a window that was legal on the plans ends up an inch too high.
Upper floors bring the opposite problem. When an operable window's opening sits more than 72 inches above the ground outside, the code wants fall protection if the sill is less than 24 inches above the floor. In practice that means either a higher sill or a window opening control device that lets the window open only a few inches until someone releases it. The device has to release easily enough that the window still works for egress. A bedroom window has to fit between those two rules: low enough to climb out of, and protected if it is low on an upper floor.
Basement bedrooms and window wells
An egress window below grade needs a window well in front of it. The well has to give at least 9 square feet of floor area, at least 36 inches out from the wall and 36 inches across, so a person can stand in it and climb out. If the well is deeper than 44 inches, it needs a permanent ladder or steps. Size the well when you size the window, since a legal window behind an undersized well still fails.
Checking egress before you order
Egress is cheap to get right on paper and expensive to fix on site. Once the units are built, a window that misses its clear opening means a new unit and sometimes a reframed opening. A few minutes with the schedule prevents it.
- Mark every bedroom and every basement with a habitable space on the window schedule.
- For each of those rooms, pick the unit that serves as the egress window.
- Get the clear opening dimensions for that exact unit from the supplier, not the rough opening.
- Check the area, the height, the width and the sill height above the finished floor.
- On upper floors, check whether that sill needs fall protection, and if so, that the device releases for egress.
If anything on the list is a close call, ask your plans examiner before the order goes in. The Washington energy code article covers the other check a bedroom window has to pass: its U-factor.
Egress windows from Puro
Puro supplies casements, single hungs and horizontal sliders built to the sizes on your schedule, so an egress window does not have to be squeezed into the nearest stock size. Every unit is NFRC certified and quoted with the glass package that meets Washington's 0.30 U-factor.
Send us your window schedule and we will price every opening, egress windows included.