Basement egress windows: code, sizes, wells, cost and install

An egress window is a window big enough and low enough to climb out of in a fire. If you're finishing an existing basement, the 2021 International Residential Code requires one in every new bedroom you add.¹ The clear opening must be at least 5.7 square feet, 20 inches wide and 24 inches high, with the sill no higher than 44 inches.¹ The average installed cost is $6,000 to $8,000.²

TL;DR

• A new bedroom is what triggers the code. Under 2021 IRC section R310.7, remodeling an existing basement doesn't by itself require an egress window. Adding a sleeping room does. Your city can be stricter.
• Size is measured at the clear opening. By our math, a 20 by 24 inch opening is only 3.3 square feet, so it fails the 5.7 square foot rule. At 20 inches wide you need about 41 inches of clear height.¹
• A 48x36 window passes or fails by style. A casement is the easiest to pass, because it meets egress at a smaller size.³ A 48-inch slider sits right at the line. A 36-inch-tall hung window usually falls short.
• Below grade, the well is half the job. It needs 9 square feet, 36 inches of projection and width, drainage and a fixed ladder once it's deeper than 44 inches.¹
• Budget $6,000 to $8,000 per window, plus a permit of $200 to $500 or more.² Cutting a foundation wall is structural work, so hire a licensed contractor who pulls the permit.

What does egress mean for windows?

For windows, egress means the window works as an emergency exit. The 2021 International Residential Code calls it an emergency escape and rescue opening. It must open from inside without keys, tools or special knowledge, and its clear opening must be big enough and low enough to climb through.¹

The word itself just means leaving a place.³ There's no special product category behind it. Any standard window counts as an egress window if it meets the size and operating rules.⁴ Casements, sliders and hung windows can all qualify when they're sized right.

The same opening works in reverse. Home Depot's buying guide notes that codes in many areas size egress windows to fit a firefighter and their equipment.³ So you're planning a way in for rescuers as much as a way out for you.

In a basement bedroom, the egress window often does a second job. The code wants habitable rooms to have glazing of at least 8 percent of the floor area, with at least 4 percent openable for fresh air.¹ There are exceptions for mechanical ventilation and artificial light, but only where the opening isn't already required as an escape opening.¹ In practice, the egress window is usually where a basement bedroom gets its daylight.

When does a basement need an egress window?

Under the 2021 International Residential Code, a basement needs an egress window in every sleeping room, and a new basement needs at least one even without a bedroom. When you finish or remodel an existing basement, section R310.7 only requires one for each new sleeping room you create.¹

Here's how the model code sorts the common cases:

• New sleeping room in an existing basement. Needs an egress window that meets the full R310.1 rules.¹
• Rec room, bar or gym in an existing basement, no bedroom. Section R310.7 says an escape opening is not required for alterations or repairs other than new sleeping rooms.¹
• New basement in an addition. Needs one, unless it already has a bedroom with an egress window or it connects to an existing basement that has one.¹
• Storm shelters and basements that only hold mechanical equipment. Exempt when the mechanical space is no more than 200 square feet.¹

Cost guides and window makers don't all read it this way. HomeGuide says codes require an egress window in each basement bedroom, office, TV room or other living space.² Pella's guide says a basement needs one if it's used as a bedroom or for habitable living space.⁵ The 2021 model text is narrower than that for existing basements. But your city adopts the code and can amend it, so the permit office's reading is the one that counts.

Plan for the window if there's any chance the room becomes a bedroom later. An office with a closet and a door is a guest room waiting to happen. Adding the window during the finish is far easier than cutting the wall after the drywall is up. If you're planning a full apartment or in-law suite, start with the basement apartments page as well.

Is it illegal to have a bedroom in the basement without an egress window?

A basement bedroom without an egress window doesn't meet the model code. Section R310.1 of the 2021 International Residential Code requires an escape and rescue opening in each basement sleeping room.¹ The one exception needs a fully sprinklered home plus required exits. How your city enforces the rule is a local matter.

That exception is narrow. The dwelling must have an automatic sprinkler system under section P2904. The basement must also have either one code-compliant means of egress plus one escape opening, or two code-compliant means of egress.¹

The practical costs show up when you sell. Pella's guide warns of fines and hardship at sale, and notes that a room without compliant egress can't be listed as a habitable bedroom.⁵ A new sleeping room also needs its own smoke alarm inside the room under section R314.3.¹ For what applies to your house, ask your local building department before you frame the room.

What are the egress window size rules?

The 2021 International Residential Code sets four numbers for an egress window. It needs at least 5.7 square feet of net clear opening, 24 inches of clear height and 20 inches of clear width.¹ The bottom of the opening can sit no higher than 44 inches above the floor.¹

Source for every row: 2021 IRC, chapter 3.¹ Your city adopts its own edition of the code and can amend these numbers.

"Net clear opening" is the part that trips people up. The code measures the opening you get from normal operation of the window.¹ The frame size on the label is always bigger than that.

Some popular guides get the numbers muddled. Home Depot's buying guide attributes the rules to the International Building Code and says basement egress windows must be at least 36 inches in width and height.³ In the 2021 residential code, that 36-inch figure belongs to the well's minimum projection and width.¹ Pella's guide gives the 5 square foot figure to openings "at ground level or lower".⁵ The code's 5 square foot exception covers grade-floor openings.¹ Plan a basement window to 5.7 unless your building department says otherwise.

State codes also vary. Massachusetts allows double-hung windows with a net clear opening of 3.3 square feet, as long as the clear opening is at least 20 by 24 inches.⁴ That allowance covers double-hung windows only.⁴

What is the smallest legal egress window?

The smallest legal egress window is one whose clear opening reaches 5.7 square feet while clearing 20 inches wide and 24 inches high.¹ You can't use both minimums at once, because by our math 20 by 24 inches is only 3.3 square feet. At 20 inches wide, you need about 41 inches of clear height.

We worked the math from the code minimums. 5.7 square feet is 820.8 square inches, and the 5 square foot grade-floor figure is 720 square inches.

Calculated from 2021 IRC R310.2.1 and R310.2.2.¹

These are clear openings, so the window you buy will measure larger. Ask for the maker's published net clear opening, because frame and rough opening sizes always run bigger.

Two situations allow smaller openings under the 2021 code:

• An existing window, where a change of occupancy requires one. An existing operable window can serve if it gives at least 4 square feet, 22 inches of clear height and 20 inches of clear width.¹
• A like-for-like replacement. A replacement for an existing egress window is exempt from the size rules if it's the maker's largest standard size that fits the existing opening, keeps the same or a larger-opening style, and isn't part of a change of occupancy.¹

Neither helps when you're cutting a new opening for a new bedroom. That window has to meet the full numbers.

Does a 48x36 window meet egress?

A 48x36 window can meet egress. The deciding number is the clear opening the sash leaves when it opens normally.¹ A 48-inch-wide slider opens roughly half its width, so it lands close to the 5.7 square foot line.⁵ Check the maker's published net clear opening before you buy.

Sliding windows

Pella's guide explains that a slider's opening is only about half as wide as the window.⁵ By our math, a 48 by 36 inch slider opens to roughly 24 inches wide. Even if the full 36 inches of height were clear, that's 864 square inches, or 6.0 square feet. That leaves only about 43 square inches over the 820.8 needed, and the frame and sash rails eat into both dimensions. Some 48-inch sliders are built and sold as egress windows. Home Depot's guide suggests sliders be at least 4 by 4 feet to meet the requirements.³ Treat a 36-inch-tall slider as borderline until the spec sheet says otherwise.

Casement windows

A casement swings open like a door, so most of the frame becomes clear opening. Home Depot's guide says this lets casements meet egress while being smaller, and lists casement egress sizes of 28 to 36 inches wide by 35 1/2 to 48 inches tall.³ A casement 36 inches wide and 48 inches tall sits at the top of that range. Check two things in a basement. The sash must swing clear of the well ladder, which the code says the open window can't block.¹ And the well must be big enough for the window to open fully.¹

Single-hung and double-hung windows

In a hung window only a sash moves up, so the clear height is a fraction of the frame height. Home Depot's guide says hung windows need to be relatively large to meet the minimum size.³ In a 36-inch-tall hung window, both sashes share those 36 inches. By our math, with equal sashes the moving one is at most 18 inches tall, short of the 24-inch minimum even before the frame takes its share. Treat a 48x36 hung window as a likely fail.

Awning windows

Awning windows hinge at the top and tilt out. Home Depot's guide lists new awning egress windows at 36 to 48 inches wide by 23 1/2 to 36 inches tall and says they often prove unsuitable for basements.³

What does an egress window well need?

An egress window whose opening sits below the ground outside needs an area well. Under section R310.4 of the 2021 International Residential Code, the well must be at least 9 square feet, project at least 36 inches from the wall, be at least 36 inches wide and let the window open fully.¹

The rest of the well rules in the 2021 code are just as specific, and local amendments can change them:

• Ladder or steps. Wells deeper than 44 inches need a permanently fixed ladder or steps, and the open window can't block them.¹ Ladder rungs need an inside width of at least 12 inches, must stand at least 3 inches off the wall and sit no more than 18 inches apart.¹ Steps need an inside width of at least 12 inches, a tread at least 5 inches deep and a riser of no more than 18 inches.¹ The ladder or steps can intrude up to 6 inches into the well's required size.¹
• Drainage. The well must drain into the house's foundation drainage system. The exception is a foundation on well-drained soil or sand-gravel mixture soils, which the code classes as Group I.¹ HomeGuide prices a drainage system at $1,000 to $4,000 where one is needed.²
• Covers and grates. Any cover, grate or bar over the well must come off from inside without a key, tool or extra force. The clear sizes still have to work with the cover in place.¹

The well's material mostly changes cost and looks. Corrugated metal wells are the cheapest. Stone or composite wells look better and cost more.² A cover keeps out debris, rain and snow. Clear polycarbonate covers let light through, while metal grate covers add security but block more light.²

Placement matters as much as material. Pella's guide advises keeping the well away from downspouts and low spots where rainwater pools.⁵ Poor drainage around a well can lead to leaks into the basement.²

What is the average cost to put in an egress window?

The average cost to put in a basement egress window is $6,000 to $8,000, with a national average of $7,000, according to HomeGuide's October 2025 cost guide.² Its full range runs from $4,000 to $12,000.² The well, the foundation type, digging access and local labor rates move the price most.

Budget from HomeGuide's $6,000 to $8,000.² Its figure is dated, states that it includes installation and lists what drives it.

HomeGuide lists what pushes a job up.²

• Window size and type. Bigger windows need more material and more foundation cutting. Vinyl frames cost least. Wood and fiberglass cost more.
• Foundation. Cutting poured concrete usually takes longer and costs more than cutting concrete block.
• Access. If equipment can't reach the spot, the crew digs by hand. Trees, shrubs or paving in the way may need to move.
• Trades. Excavation, concrete cutting, framing and window work all come from different specialists.
• Extras. Landscape repair, interior drywall and trim, and waterproofing around the cut.

HomeGuide adds that complex projects can exceed $10,000.² A deep well, a poured wall and a tight side yard together can make a job complex.

How much is a permit for an egress window?

An egress window permit typically costs $200 to $500 or more, based on HomeGuide's national cost guide.² Most municipalities require one because the job cuts into the foundation wall.² Your city's fee schedule sets the real number, so ask the permit office or your contractor for it.

Budget for the permit from the start. HomeGuide advises making the final payment only after the work passes all inspections.² That protection only works when there's a permit to inspect against. If the window serves a new bedroom, expect the inspector to look for a smoke alarm in that room too.¹

What does adding an egress window involve?

Adding a basement egress window takes seven steps. You choose the spot and pull the permit, dig the well hole, cut the foundation, set the window, install the well and drain, seal and finish, then pass inspection. HomeGuide puts a typical job at 2 to 3 days, longer when wiring or plumbing has to move.²

1. Choose the spot and pull the permit

The window needs a clear path out and a well that won't collect water. Pella's guide advises staying away from downspouts and low spots.⁵ Under a deck or porch, the code wants a clear path at least 36 inches high and 36 inches wide to the yard.¹ Inside, a wall with wiring or plumbing in it adds time, because those runs have to be rerouted.²

2. Dig the well hole

The crew excavates outside the wall for the window well.² If a machine can't reach, they dig by hand, which adds labor.²

3. Cut the foundation

This is the structural step. Pella's guide describes a masonry saw with a diamond blade and proper support to avoid structural damage.⁵ Home Depot's guide notes that making an opening taller usually takes less structural work than making it wider. A wider opening may need added horizontal support.³ Have a licensed contractor assess the wall before anyone cuts it.

4. Frame and set the window

The window goes in level and shimmed, fixed with fasteners that suit the foundation material.⁵

5. Install the well and drainage

The well is fixed to the wall and backfilled with gravel for drainage.⁵ The code expects the well to drain into the foundation drainage system unless your soil is well drained.¹ The ladder goes in now if the well is deeper than 44 inches.¹

6. Seal and finish

Waterproof flashing and sealant go around the window, and gaps get insulated.⁵ Inside, the opening needs drywall patching, trim and paint. Outside, the landscaping around the well needs restoring.²

7. Pass inspection

The inspector checks the finished opening against the permit. HomeGuide's advice to hold the final payment until inspections pass fits here.²

Can I install an egress window myself?

You can install an egress window yourself only if you have real construction experience, and most homeowners shouldn't try. The job means digging a deep hole, cutting a structural foundation wall and waterproofing the cut. Pella's guide reserves DIY for experienced DIYers who know building codes.⁵ Most municipalities still require a permit.²

The case for doing it yourself is labor cost. HomeGuide says labor is a significant share of the price because several trades are involved.² Egress window kits exist too. A kit supplies parts, though. It doesn't cut the wall for you.

The case against is what goes wrong. Pella's guide lists improper sealing, poor placement and the wrong materials as the common mistakes, and stresses proper support during the cut to avoid structural damage.⁵ Home Depot's guide says cutting or enlarging an opening takes carpentry experience, especially in solid concrete.³ A mistake in a foundation wall is expensive to undo.

A fair middle path is to hire out the cut, the well and the waterproofing. Then do the interior trim and paint yourself if you want to save something. Whoever does the work, the opening still has to meet R310 and pass inspection.

What a good egress window quote shows

A good egress window quote itemizes the window, the well, the cover, excavation, the foundation cut, drainage, the permit, interior finishing and cleanup. It names the window's net clear opening and sill height. It says whether a ladder is included and who pulls the permit. Missing lines are where surprise costs hide.

Before you sign, check that the quote answers these:

• Net clear opening. In square feet and inches, from the maker's spec. It should meet 5.7 square feet, 24 inches high and 20 inches wide.¹
• Sill height. No more than 44 inches above the finished floor.¹ Ask how the flooring you're planning affects it.
• Well size and ladder. At least 9 square feet with 36 inches of projection and width, and a fixed ladder if it's deeper than 44 inches.¹
• Drainage. How the well connects to the foundation drain, and what happens if the soil doesn't drain.¹
• Cover. Removable from inside without a key or tool.¹
• Glass. HomeGuide notes that most areas require tempered glass when a pane is over 9 square feet or the bottom edge is under 18 inches from the floor.²
• Permit and inspections. Who pulls the permit and who books the inspections.
• Yard and interior repair. Whether landscaping, drywall and trim are included.²
• Payment schedule. Final payment after the work passes inspection.²

The window is easiest to get right when it's planned with the whole basement. Settle egress with layout, moisture and ceiling height before framing starts. If you want that done in one visit, you can get a written quote for finishing your basement. Basement Remodeling Co. sends your request to one vetted, licensed basement contractor for your metro. That contractor books a free on-site estimate, checks moisture and ceiling height, and gives you a written, itemized quote. Nothing starts until you sign, and your contractor pulls the permit and books the inspections.

You can also find a basement contractor by ZIP code. If your basement is already finished and you're adding a bedroom, the basement remodeling page covers reworking finished space. Local pages show published full-finish ranges, checked September 2026:

• Basement finishing in Atlanta: $45,000 to $80,000 for a typical full finish, from one Atlanta design-build firm.
• Basement finishing in Denver: $30,000 to $90,000, from one local builder's 2026 cost guide.
• Basement finishing in Colorado Springs: $30,000 to $75,000 for a typical 1,000 square foot finish, from one local contractor's 2026 guide.
• Basement finishing in Fort Collins: $50,000 to $110,000 for a typical full finish.

Those ranges don't say whether an egress window is included, so ask for it as its own line on the quote.