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If you’re finishing a basement, or building one with a bedroom in mind from the start, the egress window opening has to be planned before the foundation wall goes in, not after. That opening starts as a wooden buck set inside the wall forms on pour day, and getting its size and placement right at that stage saves a lot of headaches once framing and window installation start.
What an egress window actually requires
Building codes require a basement bedroom, and often any habitable basement space, to have at least one egress window that can serve as an emergency exit and allow rescue access. The general requirements most jurisdictions follow, based on the International Residential Code that Ohio’s residential code is built from, call for a minimum clear opening of 5.7 square feet, a minimum clear opening height of 24 inches, a minimum clear opening width of 20 inches, and a sill height no more than 44 inches above the finished floor. Local jurisdictions can adjust some of these, so it’s worth confirming exact numbers with your building department rather than treating this article as the final word.
Why the buck has to be right before the pour
A window buck is a framed wooden box built to the exact rough opening size, braced and set into position inside the wall forms before concrete goes in. Once that concrete cures, the opening is fixed. There’s no adjusting it by an inch or two after the fact without cutting into cured concrete, which is expensive, messy, and not something any contractor wants to do on a wall that just got poured. That means the window size, sill height, and exact placement along the wall need to be finalized on the plans before form up, not decided later once framing starts.
Sill height and window wells
On a fully buried basement wall, meeting the 44 inch maximum sill height and the egress window size at the same time usually means the opening needs a window well outside, since the ground level sits well above where an egress sized window would naturally land. The well needs its own clearance requirements too, generally enough depth and width for the window to fully open and for a person to climb out, and if the well is deeper than about 44 inches, code typically requires a permanently affixed ladder or steps built into it. All of this needs to be part of the site plan, not an afterthought added after backfill.
Getting the rough opening size right
It’s worth double checking the buck dimensions against the actual egress window unit that will be installed, not just the code minimum. Different manufacturers’ egress window units have different actual glass and frame dimensions for a given “size,” and a buck built to a generic rough opening number can end up slightly mismatched to the specific window that gets ordered. We coordinate this with the homeowner or builder before form up whenever the window selection is already locked in.
Planning for a finished basement later, even if you’re not finishing it now
A common situation we run into is a homeowner pouring a basement with no immediate plan to finish it, but who wants the option open down the road. If there’s any realistic chance a basement bedroom happens in five or ten years, it’s worth setting the egress buck correctly at pour time even if the window itself doesn’t go in right away, some builders will frame the opening and install a temporary smaller window or even leave it framed and covered until the finish work happens. Retrofitting an egress sized opening into a wall that was poured without one planned for is a far bigger job than building it in from the start, even if the actual window purchase gets delayed by years.
Frequently asked
Does every basement need an egress window, even without a bedroom?
Requirements vary, but most codes require egress for any habitable space, and specifically for any room used as a bedroom. A basement used only for mechanical or storage space typically doesn’t need one, though check with your local building department.
Can an egress window buck be added to an existing poured wall later?
Yes, but it means cutting an opening into cured concrete, which is a bigger, more expensive job than setting a buck during the original pour. Planning for egress upfront is almost always cheaper.
Related reading
If you’re planning a new pour or want a second opinion on a foundation question specific to your site, reach out to Armada Poured Walls and we’ll walk through it with you.