Basement egress windows

The windows in question have sill heights of 44.5 the actual window clear openings are 46 my question is what is considered the clear openings ? Is the sill height considered part of the clear opening or is it just the actual window opening need to be at the 44 inches?

Morning, Mark. Welcome to the InterNACHI forum.
You posted, the windows in question have sill height is 44.5" inches.
Not an egress window. More than 44" inches. Its a plain window.

Egress window must be at least 5.7 square feet, 20 inches wide by 24 inches high . Its opening must be no higher than 44 inches from the floor.
Clear opening is unobstructed, nothing in the way, clear and open space to escape through. No, zero, nada, nil, absolutely no obstructions, clear path of area, no impediments, void of objects, etc…


An AHJ could interpret it any way he wants. You’re not an AHJ so take it literally in two parts. One is sill height; the other is net clear opening. Don’t combine the two. Your first measurement is sill height. Second measurement, irregardless of sill height, is net clear opening.

Don’t forget the exterior well requirements.


You’re mixing terms or confusing parts of the requirements.

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Be careful with Dominic’s document. The illustration says 5.7 sq. ft. This is an ABOVE grade egress window. At or below grade is 5.0 sq. ft.

A minimum width of 20" requires a 36 " height (5 sq, ft is 720 sq inches).

A minimum height of 24" requires a 30 inch width (24x30=720).

Note the Key word here being “NET”!

As Robert Young stated…

The graphic(s) that Bob Kenney posted shows the “GROSS” opening, and is likely why you have the wrong understanding of where the measurements are taken and what they entail…

Dominic’s posted document has proper graphics showing the actual “NET” areas that should be measured and used for determination of compliance.
Note this applies when the windows are in the “OPEN” position, especially when casement windows are installed!

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The numbers I posted are the correct clear net openings. JJ just doesn’t like where the lines are drawn. A “gross” opening is the hole a window fits into. The “net” opening is the clear open space provided by an open window. Dimensions provided are still the same. The deceptive part of Dominic’s attachment is that they don’t provide the opposite measurement with the minimum measurements. You cannot have both the minimum width and minimum height on the same window. This would only be (20x24) 480 square inches (5 square feet is 720 square inches). Again Dominic’s posting only mentions an above grade opening of 5.7 square feet while code says at or below grade openings are 5.0 square feet.

No, I don’t, because they are just WRONG!
The measured numbers mean nothing if they are taken in the wrong place, which is the problem scenario that the OP has presented… WHERE the measurements should be taken!

In Quebec, the minimum dimensions required for egress windows are 0.35 m2 (3.77 ft2), with no dimensions under 38 cm (15 in). It must also open from the inside, without keys, without tools, without special knowledge and without the need to remove a frame or hardware.

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Here I fixed it. Can’t have you bursting a blood vessel on the forum.

Are you happy now?

Note if you don’t know how to measure windows, don’t attempt this!

[quote=“ryoung7, post:2, topic:226919”
Egress window must be at least 5.7 square feet, 20 inches wide by 24 inches high .

This is wrong on 2 counts. At or below grade window need only be 5.0 square feet (720 Square inches). Secondly, as I already pointed out, a 20 inch wide opening must be 36 inches high. A 24 inch high opening must be 30 inches wide. A 20 x 24 inch opening as Young stated would only be 480 Square inches. 240 square inches shy of the needed 720.

As usual, you are missing the point!

Butthurt Cream (2)

As usual, you haven’t made one! You’re good at insults and little comics but not too good with words.

Your objection to lines appearing to indicate a “gross” opening rather than the “net” opening of the open window was addressed despite having clear specific language included. You did however miss Young’s error in dimensions. I guess you two are butt buddies now.

As far as the OP’s measurement conundrum, you assume he cannot measure when all he was doing was adding the window track height to the original sill height which is not necessary.

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I read all the comments and im still recovering…lol…let me try wording my question different. What i consider the window sill 44.5 is different from the actual vinyl window frame opening 46 the windows in question have the clear net opening requirements so my only question is which measurement is from the floor. Because one measurement is .5 out the other is 1.5 out thats a big difference!

That was answered by both Dominic and myself. The window sill height does not include any portion of the window.

Just clarification, domincs post clearly shows the 44 in measurement to the net window opening height and that is where I guess my confusion is.

Sill height of 44 in maximum is measured from the clear opening to the finished floor


Thank you for that clear answer!


Dominics illustration does not have a window “track” on the bottom of the window. As far as I’m concerned this is a limitation of the illustration (not representative of real life).

This is the exact wording:

R310.2.2 Window sill height. Where a window is provided
as the emergency escape and rescue opening, it shall
have a sill height of not more than 44 inches (1118 mm)
above the floor; where the sill height is below grade, it
shall be provided with a window well in accordance with
Section R310.2.3.

Don’t add words to the code. Measure the two items (presented separately in the code) separately. Code does not say “measured from the clear opening.”

R310.2 Emergency escape and rescue openings. Emergency
escape and rescue openings shall have minimum dimensions
as specified in this section.
R310.2.1 Minimum opening area. Emergency and
escape rescue openings shall have a net clear opening of
not less than 5.7 square feet (0.530 m2). The net clear
opening dimensions required by this section shall be
obtained by the normal operation of the emergency escape
and rescue opening from the inside. The net clear height of
the opening shall be not less than 24 inches (610 mm) and
the net clear width shall be not less than 20 inches (508
Exception: Grade floor openings or below-grade
openings shall have a net clear opening area of not less
than 5 square feet (0.465 m2).

Bear in mind also that there are provisions for finishing existing basements and when an egress window is needed (R310.6). There are also provisions for replacement windows that do not meet the above dimensions (R310.2.5).