Installing an egress window: every step, and the ones not to DIY

Installing a basement egress window runs in a fixed order: permit, utility locate, excavation, foundation cut, header or frame, window, then the well, drainage and backfill.¹² A handy homeowner can dig, set the window and trim it. Hand the concrete cut, the header and the drain tie-in to a licensed contractor. Mistakes there are structural or wet, and both are hard to undo once the well is backfilled.

TL;DR

• The 2021 International Residential Code (IRC) sets the size: at least 5.7 square feet of net clear opening, 24 inches high and 20 inches wide, with the sill no more than 44 inches off the floor.³ Local adoption varies, and your city may amend it.
• A below-grade egress window needs a well of at least 9 square feet.³ The well needs a ladder once it's deeper than 44 inches and a drain to the foundation drainage system unless the soil drains well.³
• DIY works for the paperwork, digging, window setting and trim. The foundation cut, the header and the drain tie-in belong to a licensed pro.
• Budget $6,000 to $8,000 per window installed with the well, excavation and labor.⁴⁵ Complex jobs can pass $10,000.⁴

What size does a basement egress window have to be?

Under the 2021 International Residential Code, section R310, a basement egress window needs a net clear opening of at least 5.7 square feet.³ The opening must be at least 24 inches high and 20 inches wide.³ Its bottom can sit no more than 44 inches above the floor.³ Local adoption and amendments vary, so confirm with your building department.³

The code calls this window an emergency escape and rescue opening. It's the way out of a basement in a fire, which is why the code sizes it for a person climbing through.⁴ "Net clear opening" means the gap you can actually climb through with the window opened the normal way. The code says the dimensions "shall be the result of normal operation of the opening."³ The frame, the fixed sash and the hardware don't count.

The minimum height and width don't add up to the minimum area. By our arithmetic, a 24 by 20 inch opening works out to 480 square inches, or about 3.3 square feet. The 5.7 square foot minimum works out to 820.8 square inches. At the 24-inch minimum height, that works out to a clear width of at least 34.2 inches. Our egress window requirements guide covers the sizing rules in full.

You'll also see a 5-square-foot figure in the code. That exception applies to grade-floor openings.³ Plan a below-grade basement window to 5.7 square feet and let your building department confirm.

Ask about the glass too. HomeGuide notes that most areas require tempered glass when a pane is larger than 9 square feet or its bottom edge sits less than 18 inches from the floor.⁴ For which rooms need an egress window in the first place, read our guide to basement egress windows.

What are the steps to install a basement egress window?

A basement egress window takes ten steps: permit, utility locate, marking, excavation, foundation cut, header or frame, window setting, sealing, the well with its drainage, then backfill and inspection. You need a permit, a code-sized window and a plan for the water before anyone digs. The work takes 2 to 3 days on average.⁴

Always follow the window and well makers' own instructions where they differ from a general guide. Redi-Exit, which sells egress windows, says its warranty depends on it.²

1. Pull the permit and pick the spot

Most municipalities require a permit because the job cuts into the foundation. HomeGuide puts permit fees at $200 to $500+ depending on location.⁴ If you hire the job out, your contractor pulls the permit and books the inspections. If you do it yourself, the permit and inspections are yours to arrange.

Pick a wall section clear of wires and pipes. East and south walls get the most light. Replacing an existing small basement window with the egress unit is a popular choice.²

2. Get the utilities marked

Call your local diggers hotline before any excavation so nobody hits a buried line.² The homeowner behind the biggerthanthethreeofus project listed this as step one, before the permit.¹

3. Mark the opening inside and out

Lay out the rough opening on the inside of the wall. Add any framing you plan to use, plus about 1/4 inch all around so the window can slide in. Keep the sill at 42 inches or less to stay under the 44-inch limit.² Drill through the wall at the centerline of the top and bottom of the opening. Those holes locate the cut on the outside face. Build a small frame covered in plastic inside the basement to hold back the dust.²

4. Dig the hole for the well

Redi-Exit's guide calls for a hole that's 4 feet wider at the foundation wall and 1 foot wider than the well the rest of the way around.² It goes about 19 inches deeper than the bottom of the window.² Center it on the holes you drilled. The well that sits in it must be at least 9 square feet, with 36 inches of projection and width.³

With the foundation exposed, check its waterproofing and look for other problems.¹ If equipment can't reach the spot, the crew digs by hand. That adds labor time and cost.⁴

5. Cut the foundation wall

Mark the rough opening on the outside face. Cut with a diamond-blade concrete demolition saw, starting outside.² In poured concrete the first pass goes about 1/4 inch deep. In block it can go 1 inch.² Later passes go deeper until the last cut reaches at least 3 inches or half the wall thickness. Then the same cuts go in from the inside.² The cut section breaks out with a 3-pound hammer, and a cold chisel cleans the edges.²

Redi-Exit calls the saw an unwieldy tool that throws a large cloud of dust. It tells installers to wear goggles and a tight-fitting dust mask. A water-cooled saw keeps the mess down.² Poured concrete takes longer and costs more to cut than block.⁴

6. Add the header and frame the opening

Cutting an opening removes wall that was carrying load, so the opening often needs a header (also called a lintel). Redi-Exit says to install one when ceiling joists run perpendicular to the wall, when the wall is concrete block, or when the window is a slider 48 inches wide or more.² The biggerthanthethreeofus contractors added a header right after the cut.¹ Header size is a structural call. Your contractor, or a structural engineer where your building department asks for one, should set it.

Block walls also need a frame. Hollow block is a poor anchor for a window. The frame is pressure-treated wood or a synthetic composite, glued with construction adhesive. It's nailed into the mortar joints so the hollow blocks don't crack.² A frame is optional in poured concrete.²

7. Set, shim and fasten the window

Test-fit first. Rest the window on the sill, line it up square with the opening and tip it forward into place.⁶ Shim the sill at no more than 16 inches apart and the sides at no more than 24 inches apart. Tapered wood shims go in pairs, one from each side.⁶ Measure both diagonals. When they match, the window is square.⁶

In a block wall, fasten into the wood frame with 1 1/2 inch galvanized or stainless steel screws driven through the shims. In poured concrete, use 1 1/2 to 2 inch concrete anchors. Predrill pilot holes in both cases so the vinyl frame doesn't crack. Keep every fastener out of the bottom sill, because a fastener there makes the window leak.² Then open and close the window. It has to open fully to meet code.⁶

8. Seal, insulate and trim

Run a 1 to 1 1/2 inch bead of low-expanding foam across the gap at the top and sides. Leave the rest of the gap unfoamed, since even low-expanding foam can distort the jambs.⁶ Fill the remaining gap loosely with fiberglass or rock wool.⁶ Outside, use butyl caulk or a low-temperature silicone caulk, and keep the weep holes open.²

9. Install the well, ladder and drainage

The well is a reinforced enclosure that holds back soil and leaves open space to climb out.⁴ Wells deeper than 44 inches need a permanently fixed ladder or steps that the open window can't block.³ Ladder rungs need at least 12 inches of inside width, at least 3 inches of projection from the wall and no more than 18 inches between them.³ The ladder may intrude up to 6 inches into the well's required size.³

The well drains to the foundation drainage system unless the house sits on well-drained Group I soil.³ The biggerthanthethreeofus job ran French drains to carry water away and put rock in the bottom of each well.¹ The next section covers drainage in detail.

10. Backfill, regrade and finish

Backfill around the well, regrade the yard so water runs away from the house, then reseed.¹ Inside, you may need to patch drywall, paint and add trim around the new window.⁴ Your building department sets which inspections happen and when. Ask before you backfill or close up the wall so nothing has to be uncovered for the inspector.

Can you install an egress window yourself?

You can if your building department lets homeowners pull the permit and you're ready for heavy, dusty, structural work. Manufacturer guides walk DIYers through it, and one admits it may not qualify as a basic project.⁶ The safest split: do the digging, window setting and trim yourself. Hire out the foundation cut, header and drain tie-in.

Here's how the ten steps divide.

Redi-Exit, a company that sells egress windows to DIYers, still recommends hiring a contractor for the simplest route.² The homeowner behind biggerthanthethreeofus ruled out DIY after reading what the job involved: cutting the foundation, putting in French drains and building to code.¹

Doing the heavy but simple steps yourself cuts the labor bill. The risk sits in the three steps to hand off. A bad cut or an undersized header can crack a foundation wall. A well that doesn't drain puts water against a window at the bottom of a hole. Both are hard to fix once the well is backfilled and the wall is finished.

Does an egress window need a drain?

Usually, yes. The 2021 International Residential Code, section R310.4.3, says a window well must drain by connecting to the house's foundation drainage system. The exception is a foundation on well-drained soil or a sand-gravel mix, classed as Group I soils. Local amendments vary, so your building department makes the final call.³

A well is an open hole beside your foundation. Rain and snowmelt land in it. Without a drain, that water pools against the window. HomeGuide warns that poor drainage around window wells can lead to leaks, and prices a drainage system at $1,000 to $4,000.⁴ Areas with heavy rain or a high water table may also need extra waterproofing around the window and the cut.⁴

Keep other water away from the well too. Redi-Exit says gutters, downspouts, exterior faucets, sprinkler heads and sump pump outlets should sit at least 6 to 10 feet from the well.² Regrading the yard away from the house finishes the job.¹

A cover helps keep out debris, rain and snow.⁴ If you add one, it must release from inside with no key, tool or extra force.³

What does it cost to install an egress window?

Budget $6,000 to $8,000 for one basement egress window, installed with the well, excavation and labor.⁴⁵ HomeGuide's national figures run from a $4,000 minimum to a $12,000 maximum, and complex jobs can pass $10,000.⁴ Window size, wall type, well material, site access and local labor rates move the price most.⁴

The two HomeGuide ranges disagree. The $3,000 to $7,000 figure sits in a general window table, and HomeGuide says those installed prices vary between handyman labor and an expert installer.⁵ The $6,000 to $8,000 figure comes from HomeGuide's dedicated egress guide.⁴ HomeGuide's window guide says it covers the window, a window well, excavation and labor.⁵ Budget from $6,000 to $8,000, because it prices the whole job.⁵ Our egress window cost guide breaks the price down further.

What pushes a quote up:

• Wall type. Poured concrete takes longer to cut than block.⁴
• Access. Hand digging adds labor, and trees or hardscaping may have to move.⁴
• Well material. Corrugated metal wells cost least. Stone and composite wells cost more.⁴
• Size. The biggerthanthethreeofus homeowner says a big share of their $16,000 went to excavation and stone work for oversized wells.¹ They estimate a standard well kit could have cut the cost in half.¹

Your own price depends on your wall, your soil and your yard. A contractor's on-site estimate turns these ranges into your number.

Is it illegal to sleep in a basement without an egress window?

A basement room used for sleeping needs an egress window under the model code. The 2021 International Residential Code, section R310.1, requires an emergency escape and rescue opening in every basement sleeping room. Whether breaking that rule is illegal where you live depends on your local code and how it's enforced.³

Three more model-code rules apply. Every new basement needs at least one egress opening, except a basement of 200 square feet or less used only for mechanical equipment.³ When you finish or alter an existing basement, only new sleeping rooms need one under R310.7.³ A house with an automatic sprinkler system can skip the opening in basement sleeping rooms if the basement has one code-compliant exit plus one egress opening, or two code-compliant exits.³

Local rules can go further. Ask your building department before you call a basement room a bedroom. If you plan a rental unit or in-law suite downstairs, our basement apartments page covers what that adds. Adding a bedroom to a basement that's already finished falls under basement remodeling.

What should a good egress window quote show?

Basement Remodeling Co. treats the egress window as a planning item to settle before framing, and a good quote shows it line by line. Look for the permit, excavation, cut method, header, window model and net clear opening, well, drainage, backfill and interior finish. Anything left off is a question to ask before you sign.

What to ask your contractor:

• Who pulls the permit and books the inspections?
• Does the price include the utility locate, excavation and hauling the soil?
• What is my foundation wall made of, and how will you cut it?
• What header goes in, and who sizes it?
• Which window make and style, and what is its published net clear opening and sill height?
• What is the well made of, how deep is it, and does it need a permanent ladder?⁴
• How does the well drain, and where does it tie in?
• Is backfill, regrading, landscape repair and interior trim included?

Hire a company that is licensed and insured. Pay on a schedule tied to the work, and make the final payment only after the work passes all inspections.⁴

If the egress window is part of a bigger project, start with basement finishing. Basement Remodeling Co. matches you with one vetted, licensed basement contractor for your metro. That contractor gives a free on-site estimate and a written, itemized quote, and nothing starts until you sign. Your contractor pulls the permit and books the inspections. You can read how we choose basement finishing contractors.

Local pages cover basement finishing in Atlanta, basement finishing in Denver, basement finishing in Colorado Springs and basement finishing in Fort Collins. For scale, one Colorado Springs contractor's 2026 guide puts a typical 1,000 sq ft finish at $30,000 to $75,000 (checked September 2026). An egress window is one line inside that total.