Egress Window Requirements in Utah: Sizes, Window Wells, and ADU Rules
In Utah, a legal egress window — a bedroom's or basement's emergency escape opening — needs a net clear opening of at least 5.7 sq ft, at least 24 inches high and 20 inches wide, with the bottom of the opening no higher than 44 inches off the floor. (A smaller 5.0 sq ft opening is allowed for grade-floor or below-grade windows.) These 2021 building-code minimums are the same in every Utah city; local permits and internal-ADU rules add other steps.
Best for homeowners finishing a basement or adding a bedroom — and it's not a substitute for a permit or an inspection.
Utah ADU Builders is a Utah-focused ADU planning, feasibility, and builder-matching resource — not a city, building department, law firm, or licensed contractor. We may earn compensation when homeowners request a feasibility review or get connected with local pros; that never changes how we explain Utah's rules, costs, or risks.
Last verified: July 2026 · By the Utah ADU Builders Editorial Team
On this page
- Egress requirements at a glance
- What size does an egress window have to be?
- Which rooms need an egress window?
- Window well and ladder requirements
- What if your existing window is too small?
- How egress changes for a basement ADU
- Do you need a permit?
- How much does it cost?
- Feasibility checklist
- Common egress mistakes
- What to do next
- FAQs
- Sources
What we verified for this page
- Utah's currently adopted construction code editions, including the 2021 International Residential Code (IRC) for homes and the July 1, 2026 code update (Utah HB 65)
- The 2021 IRC egress dimensions and window-well/ladder rules (IRC Section R310)
- Utah's amendments to the IRC, including the existing-bedroom egress provision
- Utah's egress-window statute (§ 10-20-606) and the internal-ADU exception to it
- Internal-ADU code-compliance and impact-fee rules (Utah Property Rights Ombudsman; §§ 10-21-303 / 17-80-303; § 11-36a-202)
- A city example (Salt Lake City Building Services) showing how the code is enforced locally
- Cost inputs — general ranges Utah installers publish, clearly labeled as estimates
Sources are listed at the bottom of this page. Local permit review is still required for any real project.
Utah egress window requirements at a glance
An "egress window" is the plain-English name for what the code calls an emergency escape and rescue opening (EERO): a window (or door) large enough for a person to climb out and for a firefighter in gear to climb in. Utah homes follow the 2021 IRC, and these are the baseline numbers.
| Requirement | Minimum (2021 IRC) | What it means in plain terms |
|---|---|---|
| Net clear opening (openable area) | 5.7 sq ft — aim for this; a 5.0 sq ft exception applies to grade-floor or below-grade openings | The actual gap when the window is open — not the glass or the frame |
| Clear opening height | 24 in | Measured on the real open path |
| Clear opening width | 20 in | Height and width and total area must all be met |
| Bottom of opening (sill) above floor | 44 in max | If the sill is higher, the window may not qualify as-is; confirm the fix in plan review |
| Window well (for below-grade windows) | 9 sq ft, with 36 in projection and width | The well must let the window open fully |
| Ladder or steps in a well | Required if the well is deeper than 44 in | Rungs at least 12 in wide, projecting 3 in, spaced no more than 18 in apart |
| Operation | From inside, no keys/tools/special knowledge | Any cover, bar, or grate must release from the inside |
Sources: 2021 IRC §§ R310.1, R310.2.1, R310.2.2, R310.2.3, R310.2.3.1, as adopted in Utah under Utah Code § 15A-2-103.
A quick note on the 2026 code change: On July 1, 2026, Utah updated its construction codes (HB 65) and moved commercial building to the 2024 International Building Code. But homes still run on the 2021 IRC for egress, so the numbers above didn't change with the update.
What size does an egress window have to be in Utah?
The Utah egress test is not one number — it's four, and they all have to be met at the same time: minimum area, minimum height, minimum width, and maximum sill height. Miss any one and the window fails, even if the others pass. The safe target is 5.7 square feet.
Measure the clear opening, not the glass
The number that matters is the net clear opening: the space actually available when the window is open in normal use. Don't measure the glass, the frame, or the rough opening in the wall — those are almost always bigger than what you can climb through (2021 IRC § R310.2.1).
Why 20 × 24 inches isn't enough
This trips up a lot of homeowners. A window at the bare minimum height and width — 20 inches by 24 inches — is only 3.33 square feet, which is well short of the required area:
To hit the area, one dimension has to grow well past its minimum. Use this to sanity-check any window before you buy it:
Clear-opening examples
| Clear width | Clear height | Opening area | Meets 5.7 sq ft? | Meets 5.0 sq ft exception? |
|---|---|---|---|---|
| 20 in | 24 in | 3.33 sq ft | No | No |
| 20 in | 36 in | 5.00 sq ft | No | Yes* |
| 24 in | 34.25 in | ~5.71 sq ft | Yes* | Yes* |
| 30 in | 28 in | 5.83 sq ft | Yes* | Yes* |
| 36 in | 24 in | 6.00 sq ft | Yes* | Yes* |
*Only if it also meets the 24-in height and 20-in width minimums, the 44-in maximum sill height, and — for below-grade windows — the window-well rules.
Most basement egress windows sit below grade, so the 5.0 sq ft exception often applies under the current 2021 code. Even so, aim for 5.7 square feet. Most egress windows are built to hit it, it removes any doubt in plan review, and it keeps you covered if your project is reviewed under a newer code edition down the road.
Which rooms in a Utah home need an egress window?
The biggest mistake is assuming "finished basement" and "bedroom" mean the same thing. Sleeping rooms are the main trigger — and in a basement, each bedroom needs its own opening. A finished (habitable) basement also needs at least one egress opening even before you add a bedroom.
| Space | Egress opening required? | Notes |
|---|---|---|
| New basement bedroom | Yes — its own opening | Every sleeping room needs one |
| Existing basement bedroom | Usually yes; a narrow exception may apply | See "older windows" below |
| Each additional basement bedroom | Yes — each needs its own | One shared window doesn't cover them all |
| Basement apartment / internal ADU | Yes — and stricter | The grandfather exception doesn't apply |
| Finished (habitable) basement | Yes — at least one | Small mechanical-only spaces (about 200 sq ft or less) are excepted |
| Finished office/den (non-sleeping) | Falls under the basement rule; confirm locally | It can't be called or listed as a bedroom without egress |
| Habitable attic | Yes | The code covers habitable attics too |
Source: 2021 IRC § R310.1.
What about the sprinkler exception?
The IRC has a narrow exception that can change basement-bedroom egress if the home has an approved fire-sprinkler system meeting specific conditions. It rarely comes into play in Utah: the state amended the IRC to remove the requirement for automatic fire sprinklers in most new homes, so the vast majority of Utah houses aren't sprinklered. Don't treat sprinklers as a shortcut around egress — if you think it might apply, it has to be confirmed in plan review.
Can a door count instead of a window?
Sometimes. A compliant emergency escape and rescue door — like a walkout — can serve the same purpose, but it has its own size and access rules and has to be reviewed as part of your permit.
What are Utah's window well and ladder requirements?
A basement egress window can fail inspection even when the window itself is big enough. If the opening sits below ground, it needs a window well with enough room for the window to open fully and for someone to escape or be rescued (2021 IRC § R310.2.3).
Well size
At least 9 square feet of horizontal area, with a projection from the wall and a width of at least 36 inches.
Ladder or steps
If the well is deeper than 44 inches, it must have a permanently attached ladder or steps — rungs at least 12 inches wide, projecting at least 3 inches, spaced no more than 18 inches apart (§ R310.2.3.1).
Drainage
Wells generally must be designed to drain (usually tied into the foundation drainage), unless the home sits on well-draining soils (§ R310.2.3.2). In Utah's freeze-thaw climate, skipping drainage is a common source of long-term water problems.
Covers, grates, and bars
Allowed, but only if they release or lift off from the inside without a key, tool, or special knowledge.
Windows under decks or porches
Possible, but the opening has to stay fully usable and keep a clear escape path (at least 36 inches high) to the yard. Decks and additions above a well are a frequent hidden problem.
What if your existing basement window is too small?
Utah has a homeowner-protective rule that most egress guides miss. If a bedroom's window met code when the bedroom was originally finished, your city generally can't force you to enlarge it — but only under specific conditions, and it does not apply if you're creating an internal ADU.
When the older-window protection can apply
Under Utah's egress-window statute (Utah Code § 10-20-606 for cities, with a parallel provision for counties) and a matching amendment in the building code (IRC § R102.7.2 as amended in Utah), a city generally can't require you to physically enlarge an existing bedroom egress window when all of these are true:
- The bedroom's window complied with the State Construction Code in effect when the bedroom was finished, and
- The home is owner-occupied, or is a detached one-to-four-family dwelling (or a qualifying townhome with a separate means of egress), and
- The existing window is smaller than current code, and
- Enlarging it would compromise the home's structural integrity, or couldn't be completed under current setback and window-well requirements.
What the protection does not do
This is where people get burned:
- The city can still require that the window be fully openable, and can prevent you from shrinking an opening that's already undersized (§ 10-20-606).
- It does not apply to an internal ADU. The moment a basement bedroom becomes part of a rental unit, this protection falls away — more on that next.
The replacement-window option
Separately, the code lets you swap in the largest standard-size window that fits your existing frame, in the same operating style, without meeting the full area and sill rules — as long as it isn't part of a change of occupancy (2021 IRC § R310.2.5). It's a practical middle path for older homes, but confirm it with your building department before relying on it.
How egress rules change for a basement apartment or internal ADU
Here's the part that turns a simple window question into a bigger decision. An ADU (accessory dwelling unit) is a second, smaller home — either a separate structure or a unit inside an existing house. An internal ADU is one created inside an owner-occupied single-family home for long-term rental (30 days or more) — a basement apartment is the classic example. Utah's code sources treat internal ADUs more strictly than an ordinary existing bedroom.
An internal ADU is not just "an old basement bedroom"
By law, an internal ADU must comply with all applicable building, health, and fire codes (Utah Code §§ 10-21-303 and 17-80-303; Utah Property Rights Ombudsman). That means the egress opening in every sleeping room is expected to meet current code — you generally can't lean on the older-window protection above, because that protection specifically excludes internal ADUs (§ 10-20-606).
Practical translation: a basement bedroom that was fine for your family can require a full egress upgrade the day you turn the space into a rental unit.
Egress is only one piece of ADU legality
Even if the window is solvable, an internal ADU still has to clear zoning, permits, fire separation between units, its own smoke and carbon-monoxide alarms, ceiling height, utilities, and — depending on your city — parking, owner-occupancy (the owner living on-site), or rental-license rules.
One useful piece of good news: constructing an internal ADU within an existing primary dwelling is not subject to impact fees — the one-time fees some cities charge new construction to fund infrastructure (Utah Code § 11-36a-202). That exemption is specific to impact fees; it doesn't waive building-permit or plan-review fees, utility or connection charges, or the cost of the egress and code work itself.
Because the answer depends on your specific lot, foundation, city, and how you plan to use the space, the smartest move before spending on window work is a feasibility check.
Thinking about a basement apartment or internal ADU? Find out whether your basement is a realistic candidate — and what egress and code work it would take — before you pay anyone to cut concrete.
Check ADU feasibilityDo you need a permit to add or enlarge an egress window in Utah?
Yes — treat it as permit-and-inspection work, not a casual window swap. How involved it gets depends on the scope: replacing an insert is very different from cutting a foundation wall or converting a room's use.
Like-for-like replacement
May be reviewed more simply, but you can't reduce an already-undersized opening, and swapping a window doesn't by itself make a room a legal bedroom.
Enlarging an opening or cutting the foundation
This is structural work. Excavation, foundation cutting, a new header, drainage, and the window well all come into play, and professional review matters.
Turning a room into a bedroom, or creating an internal ADU
The egress question becomes part of a broader building-code and zoning review.
The egress dimensions themselves are set by the statewide construction code and don't change from city to city. What varies locally is how the code is enforced, plus zoning, ADU, rental-licensing, parking, and administrative requirements that can add to your project. Your local building department is the authority having jurisdiction. For example, Salt Lake City applies the building and fire codes in effect on the date your permit submission is accepted for review (Salt Lake City Building Services).
Bring these to any feasibility or estimate conversation:
- →Your city and property type
- →What the room will be (bedroom, office, apartment, ADU, or not sure yet)
- →The window's current clear width and height
- →The sill height (floor to the bottom of the opening)
- →Inside and outside photos
- →Window-well width, projection, and depth
- →Whether a ladder, steps, or cover exists
- →Whether the space will be rented
How much does an egress window cost in Utah? (estimates, not quotes)
Egress can be a modest line item or a real feasibility problem, depending on whether you're replacing a window, cutting a foundation, digging a new well, fixing drainage, or converting a whole basement. Treat the ranges below as estimates, not quotes.
| Scenario | General range* | Main cost drivers |
|---|---|---|
| Replace or enlarge an existing below-grade window | ~$1,000–$5,000 | Size change, well upgrade, interior finish work |
| New cut-in through the foundation (excavation + new well + drainage) | ~$3,000–$7,500+ | Excavation depth, concrete cutting, structural header, well size, drainage, patching |
*These are general figures Utah remodelers and window installers publish for 2026 — not project quotes, and not our own dataset. What they include varies (excavation, foundation cutting, well, drainage, and interior finishing all move the number). Your cost depends on your foundation, depth, drainage, and finishes. For a project-specific figure, see our Utah ADU cost guide or run a feasibility check.
Lower-friction situations tend to be:
- ↓Rough opening already close to compliant
- ↓Sill height already works
- ↓Well is big enough or easy to modify
- ↓No drainage or structural surprise
Higher-friction situations usually involve:
- ↑Cutting the foundation
- ↑Excavating a new well
- ↑Correcting drainage
- ↑Window under a deck
- ↑Tight setbacks
- ↑Multiple bedrooms each needing their own opening
An egress window isn't automatically a small fix, and a basement isn't automatically a smart ADU just because Utah has become more ADU-friendly. The right project depends on your lot, foundation, city, budget, and use case. If enlarging the window turns out to be expensive or impractical, the better decision might be a different ADU path entirely.
A feasibility checklist before you request bids
Before you call an installer, answer one question first: what am I trying to make this space become? The right answer changes depending on whether it's a bedroom, a non-sleeping room, a basement apartment, or an internal ADU.
- 1
Identify the use case
Existing bedroom, new bedroom, office/den, basement apartment, internal ADU, or not sure.
- 2
Measure the clear opening
Width × height ÷ 144 = square feet. Compare against the 5.7 sq ft target (with the 5.0 sq ft exception for grade-floor or below-grade openings), plus the 24-in height and 20-in width minimums.
- 3
Measure the sill height
Floor to the bottom of the opening — it must be 44 inches or less.
- 4
Measure the window well
Width, projection from the wall, and depth. Note whether a ladder or steps exist and whether the window can open fully.
- 5
Look for hidden blockers
A deck above the well, utilities near the cut location, foundation cracks, drainage or water issues, tight side-yard setbacks, HOA or historic-district rules, and — if you're renting — parking or owner-occupancy limits.
Not sure whether your basement window is a quick fix or a dealbreaker? A feasibility review looks at your lot, foundation, and use case together, so you know the real path before you spend.
Request a Utah ADU feasibility reviewCommon egress mistakes that fail inspections or derail ADUs
Most of these happen before anyone applies for a permit:
Measuring the glass or the rough opening instead of the net clear opening.
Assuming a 20 × 24-inch window is big enough (it's only 3.33 sq ft).
Forgetting the 44-inch maximum sill height.
Assuming one basement window covers every bedroom.
Ignoring the window-well size and projection.
Adding a cover, grate, or bar that can't release from the inside.
Forgetting the ladder or steps required in a well deeper than 44 inches.
Putting the escape path under a deck that blocks it.
Shrinking an already-undersized window during a replacement.
Assuming "grandfathered" applies to an internal ADU (it doesn't).
Getting bids before deciding whether the space is a bedroom, a rental, or an ADU.
Treating egress as the only ADU issue, when zoning, fire separation, and utilities also apply.
What to do next if your window doesn't meet Utah egress requirements
Don't start with “who can cut this window bigger?” Start with “what do I want this space to legally and safely become?” The right next step depends on the answer.
If it's just a bedroom for your household
Measure and document the opening, sill, and well, and confirm the egress path before you label or list the room as a bedroom.
If it's a basement apartment or internal ADU
Run a feasibility check first. Egress is one of several make-or-break issues, and the older-window protection won't cover you.
If the window is genuinely hard to enlarge
Consider whether a different ADU type — a garage conversion, an attached unit, or a detached ADU — is the lower-risk path for your property.
If you're getting ready for estimates
Collect your measurements and photos first so the people you talk to can actually help you.
Check feasibility before you commit to the wrong build path. We'll help you see what your property can realistically support — starting with feasibility, then cost, then connecting you with local professionals.
See what kind of ADU your property may supportRelated guides
Legal Basement Apartment Utah
What it takes to make a basement unit fully legal.
Utah ADU Permit Guide
Permit steps, timelines, and what to expect.
Utah ADU Cost Guide
Cost ranges by type, city, and project scope.
Detached ADU Builders Utah
Backyard cottage and separate-structure options.
Utah ADU Laws 2026
Current rules, citations, and what's statewide vs. local.
Utah ADU Laws Changelog
What changed in 2021, 2025, and 2026.
Frequently asked questions
Sources
- Utah Code § 15A-2-103 — Adopted editions of the State Construction Code (2021 IRC for residential)
- Utah HB 65 (2026 General Session) — Construction Code Amendments (2026 code update)
- 2021 International Residential Code, Section R310 — Emergency Escape and Rescue Openings (ICC Digital Codes)
- Utah Code § 10-20-606 — Changes to dwellings, egress windows (recodified in 2025 from former § 10-9a-511.5)
- Utah Code §§ 10-21-303 and 17-80-303 — Internal accessory dwelling units
- Utah Property Rights Ombudsman — Accessory Dwelling Units legal topic
- Salt Lake City Building Services — Current Building Codes (example of local enforcement)
- Utah Code § 11-36a-202 — Impact fees (internal ADU exemption) — available at le.utah.gov
This page is a plain-language summary for Utah homeowners, not legal, engineering, or contractor advice. Codes and ordinances change and are interpreted locally; confirm requirements for your specific address and project through local permit review.
Start a Utah ADU feasibility review
Egress is one piece of the puzzle. Your lot, city, zoning, and use case decide whether a basement ADU is a realistic path — or whether a different build type makes more sense. Check feasibility before requesting bids.
Check your property before requesting quotes