Egress windows: what they are and what the code requires

What is an egress window?

The code calls it an emergency escape and rescue opening. It needs a clear opening large enough to climb through, a sill low enough to get over, and hardware anyone can work from inside without keys, tools or special knowledge.

The most common mistake I see is someone looking at a big window and assuming it’s an egress window. Then you open it, and the space you can actually climb through is much smaller. I also see:

• sills that are too high;
• double-hung windows that look big but open very little;
• furniture blocking the way, or a bed in front of the window;
• security bars;
• locks that are hard to work;
• window wells full of stuff;
• covers that can’t be opened easily from inside;
• broken cranks or hardware;
• windows painted shut or practically stuck to the frame;
• and, now and then, a basement bedroom that never had a proper way out.

When a basement egress window is required

In Virginia, the residential code (R310.1, as amended) requires at least one operable emergency escape and rescue opening in basements, habitable attics and every sleeping room shown on the construction documents. If a basement has bedrooms, each bedroom needs its own. The opening has to lead to a public way, or to a yard or court at least 36 inches wide that leads to one. The exceptions include storm shelters, basements used only for mechanical equipment and no larger than 200 square feet, and homes with an approved automatic sprinkler system throughout.

For existing homes, the code is narrower. New bedrooms created in an existing basement need an egress opening; other alterations or repairs to an existing basement don’t trigger one on their own (R310.7). Local practice adds its own details. Fairfax County’s guide to finished basements, for example, requires an opening in basements of houses built after October 1, 2003, and in every basement bedroom, and strongly recommends one in older houses. Other states and localities can set different rules, so check with your building department.

It often comes up too late. When people finish a basement on their own, they may not think about it until they apply for a permit, the inspector sees the bedroom, they sell the house, a home inspector flags it, or a buyer asks whether the room can really be listed as a bedroom. I would rather the question come up before the drywall goes up, not when everything is finished. See finishing a basement.

Egress window size requirements

The clear opening has to be reached by opening the window the normal way from inside, and Virginia counts tilting or removing the sash as normal operation. These egress window dimensions are Virginia’s figures under the 2021 code. Other states adopt their own editions and amendments.

The minimums don’t add up on their own. An opening exactly 24 inches high and 20 inches wide is only 480 square inches, about 3.3 square feet. To reach 5.7 square feet (about 821 square inches), an opening 20 inches wide has to be just over 41 inches high, and one 24 inches high has to be about 34 inches wide. (Worked example; measure your own window’s clear opening.)

Casement, slider or double-hung

A casement swings open on side hinges, so most of its frame becomes clear opening. A slider or a double-hung only opens part of its frame, because one sash stays in place. That’s why a double-hung can look big and still fall short, unless the sash tilts or comes out as part of its normal operation. Whatever the type, measure the clear opening with the window fully open.

If you’re only replacing an existing window, Virginia’s code exempts the replacement from the size rules when it’s the manufacturer’s largest standard size that fits the existing frame or rough opening, it’s the same operating style or one with an equal or larger opening, and it isn’t part of a change of occupancy (R310.5).

Egress window wells

When the bottom of the opening sits below the ground outside, the window needs a window well large enough to open the window fully and climb out: at least 9 square feet, at least 36 inches out from the wall and 36 inches wide, with a permanent ladder or steps if it’s more than 44 inches deep (R310.4). Details, drainage and covers are in egress window wells.

Cutting a new opening in a foundation wall

Daniel Mercer’s first question is what that part of the wall is carrying. Before cutting, he wants to know:

• the floor joists and which way they run;
• bearing walls and beams above;
• the number of stories;
• the distance to corners;
• other openings nearby;
• the wall’s thickness and material;
• any existing reinforcement.

When you enlarge an opening, you remove part of a wall that was carrying load and resisting the soil pushing from outside. The opening may need a header or lintel, reinforcement at the sides, steel, reinforced concrete or a specific detail around it. It isn’t just a matter of cutting a rectangle and putting in a window.

With poured concrete, the wall is one solid piece. Daniel needs to think about the existing reinforcement, how the cut goes around the bars, how much wall is left on each side and how the loads above the opening get carried around it. A concrete saw can make a very clean cut, but that doesn’t make the opening structurally right. Block is different. Cutting it can leave blocks only partly supported and break the path the load follows through the masonry. It often needs a lintel or a reinforced bond beam and properly built sides, and he wants to know whether the cells are grouted or reinforced. You can’t see that from outside and assume it. In both cases the structure matters; block just leaves less room to improvise.

He would ask for an engineer before cutting if:

• the opening is being enlarged significantly;
• the cut is under a bearing wall or a concentrated load;
• it’s a poured wall with unknown reinforcement;
• it’s a block wall that needs a new lintel;
• the opening is near a corner or another door or window;
• the wall is tall;
• the ground outside is high against that part of the wall.

And he would stop right away if he saw horizontal cracking, bowing, displaced block, significant stair-step cracking, settlement, deteriorated masonry or a crack running through the area where the opening will go. See horizontal cracks and bowing walls.

On distance to a corner, he doesn’t have a universal number that says a certain number of inches is safe. The less wall left between the opening and the corner, the more he wants to check how that section is working. That’s structural judgment, not a code figure for every house.

Permits and who to call

Daniel expects a building permit and plan review for a new opening in a foundation wall. In Fairfax County, for example, “installing new window openings” is listed among residential projects that need a permit, while a direct replacement of an existing window doesn’t (Fairfax County). The county’s finished basement details say that cutting openings in exterior basement walls is outside their standard details, so plans have to be submitted, and a new window well needs a plan submission too (Fairfax County, Typical Finished Basement Details). Exactly which drawings or calculations a reviewer asks for depends on the opening and the locality; not every building department in Virginia asks for the same package.