Awaiting expert review. This page covers safety or regulatory rules that change over time. It is kept out of search results until a qualified reviewer has checked it; the sources below are dated so you can verify each point.
Quick answer
An egress window is a window large enough, low enough and easy enough to open that a person can climb out of a bedroom or basement in a fire and a firefighter can climb in, built to the emergency escape and rescue opening rules of the residential building code.
The International Residential Code (IRC) calls it an emergency escape and rescue opening. The 2021 IRC sets the net clear area, height, width and sill height, plus rules for window wells.
Quick facts
The key facts about Egress Window, with sources:
- Code name
- Emergency escape and rescue opening (IRC Section R310 in the 2021 edition) 1
- Minimum height and width (R310.2.2)
- 24 in high and 20 in wide 1
- Window well (R310.4.1)
- At least 9 sq ft, 36 in projection and width; ladder if deeper than 44 in 1
- 2024 IRC numbering
- The same provisions appear as Section R319 in a state proposal based on the 2024 IRC 4
Key takeaways
- Every sleeping room and most basements need at least one emergency escape and rescue opening under the IRC.
- The 2021 IRC sets 5.7 sq ft of net clear opening, at least 24 in high and 20 in wide, with the sill no higher than 44 in.
- Using the minimum height and minimum width together does not reach 5.7 sq ft; the window must be bigger in at least one direction.
- Below-grade windows need a window well of at least 9 sq ft, with a fixed ladder or steps if it is deeper than 44 in.
- Turning a basement room into a bedroom triggers the requirement; local adoption and amendments vary.
What makes a window an egress window
Any window can be opened. An egress window is one that meets the code’s escape and rescue rules.
In the 2021 IRC as reproduced by the City of Aberdeen, Washington, Section R310.1 requires basements, habitable attics and every sleeping room to have at least one operable emergency escape and rescue opening, and each sleeping room in a basement needs its own 1.
The opening must lead to a public way, or to a yard or court that opens to one 1.
The opening must work without keys, tools or special knowledge 12. Window opening control devices and fall prevention devices complying with ASTM F2090 are allowed on egress windows when they are no more than 70 in above the floor 1.
The size rules are not arbitrary. A Minnesota code proposal quotes the ICC code commentary: the 20 in width and 24 in height came partly from San Diego Building and Fire Department testing of what a firefighter with gear and a ladder needs 4.
How the four size rules work together
All four checks apply at once, measured on the clear opening you get by normally opening the window, not on the frame size 1.
- Net clear area. At least 5.7 sq ft; 5 sq ft is allowed for grade-floor openings (R310.2.1) 1.
- Net clear height. At least 24 in (R310.2.2) 1.
- Net clear width. At least 20 in (R310.2.2) 1.
- Sill height. The bottom of the clear opening no more than 44 in above the floor (R310.2.3) 1.
Net clear area (sq ft) = Clear width (in) × Clear height (in) ÷ 144
Clear width- Measured inside the opened sash, at least 20 in
Clear height- Measured inside the opened sash, at least 24 in
144- Square inches in one square foot
The result must be at least 5.7 sq ft (5 sq ft at grade floor) under the 2021 IRC; for example, 24 in × 34.2 in ≈ 5.7 sq ft.
Source: [1]
Aberdeen’s handout points out the trap: 20 in × 24 in is only 480 sq in, while 5.7 sq ft is 821 sq in 1. A window meeting both minimums still fails the area rule.
Types of emergency escape openings
| Opening | Why it can work | Watch for |
|---|---|---|
| Casement window | Swings fully open, so clear area is close to frame size | Crank hardware must allow full opening |
| Sliding window | Half the sash opens | Needs a wide unit to reach 5.7 sq ft |
| Double-hung window | One sash moves up | Needs a tall unit; clear height is about half |
| Side-hinged or sliding door | Doors qualify as emergency escape openings 2 | Must lead to a yard or court |
| Bulkhead (exterior basement door) | Stair access from a basement | Covers and devices must still release from inside 1 |
| Opening under a deck or porch | Allowed if fully openable with a 36 × 36 in path out (R310.2.4) 1 | Path height and width |
Example: checking a basement bedroom window
A homeowner is finishing a basement and adding a bedroom. The window below sits partly below grade. Every requirement comes from 2021 IRC text as reproduced by the City of Aberdeen 1; the dimensions are example inputs.
| Check | 2021 IRC requirement | Example window | Result |
|---|---|---|---|
| Clear width | 20 in minimum (R310.2.2) | 32 in casement | Pass |
| Clear height | 24 in minimum (R310.2.2) | 30 in | Pass |
| Clear area | 5.7 sq ft (R310.2.1) | 32 × 30 ÷ 144 = 6.67 sq ft | Pass |
| Sill height | 44 in maximum (R310.2.3) | 46 in above the floor | Fail: lower the sill or add a permanent step per local approval |
| Window well area | 9 sq ft, 36 in projection and width (R310.4.1) | 40 in wide × 36 in out = 10 sq ft | Pass |
| Well depth | Ladder or steps if deeper than 44 in (R310.4.2) | 52 in deep | Needs a fixed ladder: rungs 12 in wide, 3 in off the wall, 18 in apart max |
This window passes on size and fails on sill height. In a basement, lowering a sill usually means cutting the foundation wall, which is structural work. Boulder County, for example, requires foundation-wall cuts to be designed or inspected by a Colorado-licensed design professional 2. Use our permit checker before planning the cut.
Where egress rules show up in a remodel
Basement finishing. The 2021 IRC requires an emergency escape opening when a new sleeping room is created in an existing basement; other basement alterations and repairs do not trigger one (R310.7) 1.
Additions. Each new sleeping room in an addition needs one, and a new basement in an addition generally needs one, with exceptions (R310.6) 1.
Window replacement. Replacements can be exempt from the size rules if they are the maker’s largest standard size that fits the existing frame or rough opening and are not part of a change of occupancy (R310.5) 1. Measure the rough opening before ordering.
On the plans and permit. Bedroom windows are labelled with their net clear opening and sill height, and inspectors check them before the final.
Frame size is not clear opening
The code measures the net clear opening produced by normally opening the window, not the rough opening or frame size 1. Ask the window supplier for the net clear width, height and area of the exact unit.
What an egress window adds, and what it costs you in design
Benefits
Design costs
Limits: security bars, decks and old windows
Security devices are allowed only if they keep the full clear opening and release from inside without a key, tool or more force than normal opening (R310.4.4) 1. Fixed bars on a bedroom window defeat the purpose.
Decks and porches over an egress window are allowed only if the window opens fully and leaves a path at least 36 in high and 36 in wide to a yard or court (R310.2.4) 1.
Older homes are a gray zone. Existing windows that met the code when installed generally remain unless the work triggers the rules.
In a change of occupancy that newly requires an opening, the 2021 IRC accepts an existing operable window with at least 4 sq ft net clear, 22 in high and 20 in wide (R310.7.1) 1.
Minnesota notes it did not require these openings until 1972 and has proposed tighter local rules for replacement windows 4. Local amendments decide.
What drives egress window cost, and how long it lasts
We do not publish prices. The big drivers are whether the foundation must be cut (and engineered), excavation for the window well, the well itself and any ladder or steps, drainage to the foundation drain (R310.4.3) 1, the window unit, interior trim and drywall, permits and inspections, and site access.
An above-grade bedroom window that only needs a larger unit is a much smaller job than a basement egress cut.
The window follows normal window life; the well and drainage need upkeep to stay clear. The cost guide and whole-home budget tool show where basement work fits a project budget.
How an egress window project usually runs
Expect a building permit. Foundation cuts typically need a design by a licensed engineer or other design professional, and the work should be done by a licensed contractor.
- Confirm which code edition your city adopted and any local amendments.
- Measure the room and pick a window whose net clear opening meets the size and sill rules 1.
- If a foundation wall will be cut, get the cut and header designed by a licensed design professional 2.
- Apply for the permit with the plan, window spec and well detail.
- Excavate, cut and frame the opening as designed; install the window.
- Install the well (9 sq ft minimum, 36 in projection and width), drainage and any ladder (R310.4) 1.
- Finish interior trim; pass inspection before the room is used as a bedroom.
Keeping an egress window usable
- Open it twice a year to make sure the sash and hardware still work without tools 1.
- Clear the window well of leaves, snow and stored items; the well must let the window open fully 1.
- Keep the well drain working so water does not pool against the window.
- Check well covers release from inside 1.
- Do not block it with furniture, air conditioners or fixed screens.
Warning signs and when to call a pro
- A basement bedroom with no qualifying window: an unpermitted bedroom and a life-safety gap.
- Window painted or screwed shut, or hardware that sticks.
- Fixed bars or a heavy grate over the well.
- Water in the well or leaks at the window after rain.
- Cracks around a past foundation cut: have a structural engineer look.
Foundation cuts and old paint need professionals
Cutting a basement wall for an egress window changes the structure and can undermine the wall if not designed; have a licensed engineer or design professional design it, use a licensed contractor and get a permit 2.
In homes built before 1978, replacing windows disturbs painted surfaces, and EPA’s RRP rule requires certified firms using lead-safe practices for paid work 5.
Which code rules apply, and in which edition
2021 IRC Section R310 (new work and additions). R310.1 (where required, operation), R310.2.1 to R310.2.4 (5.7 sq ft area, 24 in height, 20 in width, 44 in sill, decks and porches), R310.4.1 to R310.4.4 (area wells, ladders and steps, drainage, bars and covers), R310.5 (replacement windows), R310.6 (additions), R310.7 and R310.7.1 (alterations of existing basements and existing openings) 12.
2024 IRC. The same topic appears under Section R319 (for example R319.5 for replacement windows) in a Minnesota proposal written against the 2024 IRC 4. If your jurisdiction adopted the 2024 edition, expect the new numbers.
State and local amendments. States adopt editions on their own schedules and amend them; St. Paul’s handout is based on the 2020 Minnesota Residential Code 3. Alterations to existing buildings may also fall under the International Existing Building Code (IEBC) where adopted; see our existing building code entry.
Lead rules. EPA’s RRP rule (40 CFR 745) covers paid window work in pre-1978 homes 5.
Egress window vs other openings
| Opening | Main purpose | Size rule |
|---|---|---|
| Egress window (EERO) | Escape and rescue from sleeping rooms and basements 1 | 5.7 sq ft, 24 in H, 20 in W, sill ≤ 44 in |
| Ordinary bedroom window | Light and air | Light and ventilation rules only |
| Existing window in a change of occupancy | Accepted escape opening if it qualifies (R310.7.1) 1 | 4 sq ft, 22 in H, 20 in W |
| Replacement window (R310.5) | Swaps an existing unit 1 | Exempt from size rules if largest standard size that fits |
| Means of egress door | Main exit path (separate IRC section) | Door and stair rules |
Egress window myths
- Myth A 20 × 24 in opening meets code.
- Reality That is only about 3.3 sq ft; the area rule needs 5.7 sq ft 1.
- Myth Frame size is what counts.
- Reality The code measures the net clear opening when the window is opened normally 1.
- Myth Every basement remodel needs a new egress window.
- Reality Under 2021 IRC R310.7, only new sleeping rooms trigger it in existing basements 1.
- Myth Replacement windows must always meet full size.
- Reality R310.5 exempts qualifying replacements; some states amend this 14.
- Myth Security bars are fine if you have a key.
- Reality Devices must release without keys or tools 1.
Local adoption: editions and amendments differ
Egress rules come from the residential code each state or city adopts.
Minnesota’s code places them in its own residential code (St. Paul’s handout cites the 2020 Minnesota Residential Code) 3, and the state has proposed stricter replacement-window rules because it did not require these openings until 1972 4.
Colorado counties may require a licensed design professional for foundation cuts 2.
Frost depth and soil type also shape window well drainage, which the IRC ties to the foundation drain unless soils are well drained 1. Check with your building department or our permits guide.
When you need an egress window, and the next step
You need one whenever a room will be used for sleeping, in most basements in new construction and additions, and when you create a bedroom in an existing basement. You usually do not need a new one for basement work that adds no bedroom, or for qualifying replacement windows, under the 2021 IRC.
The next step is confirming your local code edition and amendments, then getting the window size and any foundation cut designed before buying a window. This page is held for review by a licensed building official before publication.
- If Adding a bedroom in a basement
- Then Egress opening required in that bedroom (R310.7) 1
- If Finishing a basement rec room, no bedroom
- Then Not required for alterations (R310.7) 1
- If Replacing an existing bedroom window
- Then May be exempt under R310.5 if it is the largest standard size that fits 1
- If Window sill below grade
- Then Window well of 9 sq ft; ladder if deeper than 44 in (R310.4) 1
- If Foundation wall must be cut
- Then Licensed design professional and permit 2
Questions about Egress Window
What size does an egress window have to be?
Under the 2021 IRC, the net clear opening must be at least 5.7 square feet, or 5 square feet at grade floor, with a clear height of at least 24 inches and a clear width of at least 20 inches.
The sill can be no more than 44 inches above the floor. Check your local code edition.
Does every bedroom need an egress window?
Under the IRC, every sleeping room needs at least one operable emergency escape and rescue opening, which can be a qualifying window or an exterior door. There are limited exceptions, such as certain sprinklered basements with other exits. Local amendments can change the details.
Does a basement need an egress window?
In new construction and additions, basements generally need one under the IRC, and every basement bedroom needs its own. When altering an existing basement, the 2021 IRC requires one only if you create a new sleeping room; other alterations and repairs do not trigger it.
How big does an egress window well need to be?
Under 2021 IRC R310.4.1, the well needs a horizontal area of at least 9 square feet, with a projection and width of at least 36 inches, and must let the window open fully. If it is deeper than 44 inches, it needs a permanently attached ladder or steps.
Do replacement windows have to meet egress size?
Not always. The 2021 IRC exempts a replacement window from the size rules if it is the maker’s largest standard size that fits the existing frame or rough opening, is the same style or opens at least as large, and is not part of a change of occupancy. Some states amend this rule.
What is the maximum sill height for an egress window?
Forty-four inches from the floor to the bottom of the clear opening, under 2021 IRC R310.2.3. If a basement window sits higher, the options are usually a lower window, which often means cutting the foundation, or another approach your building department accepts.
Can I put bars on an egress window?
Only if they release from inside without a key, tool or more force than it takes to open the window normally, and the full clear opening is kept, under 2021 IRC R310.4.4. Fixed bars on a bedroom window are not allowed.
Do I need a permit for an egress window?
Usually yes, especially when a foundation wall is cut or a window opening is enlarged. Cutting a foundation is structural work, and some jurisdictions require a licensed design professional to design or inspect it. Check with your building department before you start.
What changed for egress windows in the 2024 IRC?
The most visible change is numbering: a Minnesota proposal written against the 2024 IRC cites the emergency escape rules under Section R319 instead of R310. Confirm the exact text in the edition your jurisdiction adopted, since local amendments can also change the requirements.
Sources
- City of Aberdeen (WA) Building Department, Emergency Escape and Rescue Openings (Egress), IRC 2021 Section R310 handout, retrieved .
- Boulder County (CO), Building Publication B10: Emergency Escape and Rescue Openings (2021 IRC), retrieved .
- City of Saint Paul DSI, Emergency Escape and Rescue Openings, Section R310 of the 2020 Minnesota Residential Code, retrieved .
- Minnesota Department of Labor and Industry, Residential TAG code change proposal: EERO (2024 IRC R319.5, R319.6, R319.7.1), 2025, retrieved .
- U.S. EPA, Lead Renovation, Repair and Painting Program, retrieved .
Expert review
Written by the HyreRemodel Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Every dimension and section number is quoted from 2021 IRC Section R310 text reproduced in the City of Aberdeen handout and cross-checked against Boulder County’s 2021 IRC publication; the ICC code viewer blocked automated access on the retrieval date.
The 2024 renumbering to R319 is from a Minnesota DLI proposal written against the 2024 IRC. The worked example uses illustrative window dimensions.
Held under G-REV: noindex until a licensed building official or ICC-certified inspector reviews it. No prices are given.
Suggest a correction. We fix errors and say what changed.