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The checklist
| Requirement | IRC | Value |
|---|---|---|
| Emergency escape opening | R310 | 5.7 sq ft net, 24 in high, 20 in wide, sill ≤ 44 in |
| Window well, if below grade | R310 | 9 sq ft, 36 in each way |
| Ceiling height | R305 | 7 ft; 6 ft 4 in under beams and ducts |
| Floor area | R304 | 70 sq ft minimum |
| Horizontal dimension | R304 | 7 ft minimum |
R304 values from ICC's Residential Inspector's Guide sample.
Smoke and carbon monoxide alarm rules and heating requirements also apply; check your local adoption. Appraisers report a finished basement bedroom with the below-grade area, not as above-grade living area.
| Requirement | Minimum or maximum | IRC section |
|---|---|---|
| Net clear opening | 5.7 sq ft (5.0 sq ft at grade floor) | R310 |
| Clear opening height | 24 in minimum | R310 |
| Clear opening width | 20 in minimum | R310 |
| Sill height above floor | 44 in maximum | R310 |
| Window well area | 9 sq ft minimum | R310 |
| Well width and projection | 36 in minimum each | R310 |
| Well deeper than 44 in | Permanently attached ladder or steps | R310 |
Subsection numbers differ between IRC editions; the values are the same in the 2012–2021 city handouts cited below.
Worked example
A casement with a clear opening 24 in wide and 41 in tall gives 984 sq in, or 6.83 sq ft, which passes 5.7. Set in a 40 in sill, the opening's bottom is 4 in under the 44 in limit, so a 2 in subfloor and flooring still leave room. The same opening in a slider would need a frame roughly twice as wide because only one sash moves. Outside, a 40 × 38 in well gives 10.6 sq ft and passes; at 52 in deep it needs a fixed ladder.
Where basement inspections usually fail
- Bedroom windows that are too small or too high, especially sliders and double-hungs measured by the frame instead of the opening.
- Window wells under 36 in deep from the wall, or deeper than 44 in with no ladder.
- Ceilings that dip under 6 ft 4 in at a duct or beam once drywall and flooring go in.
- Stairs with a short top or bottom riser after new flooring changes the floor levels.
- Missing fire blocking at the top of furred walls and around soffits.
Many cities publish one-page handouts on these items, like the St. Paul, Boise and Des Moines sheets cited on this site. Ask for your city's version before you frame.
Before you call for an inspection
- Measure every egress opening with the sash open and write the numbers on the frame.
- Measure ceiling height at the lowest duct or beam after the ceiling material is up.
- Check riser heights top and bottom after flooring.
- Leave insulation and vapor details visible until the insulation inspection if your town does one.
- Have the permit card and approved plans on site.
Common questions
Can a basement bedroom have no window?
Not under the IRC. Every sleeping room needs an emergency escape and rescue opening, which can be a window or a door to the outside.
Related calculators
Sources
- https://www.stpaul.gov/sites/default/files/Media%20Root/Safety%20&%20Inspections/DSI.Bldg_EgressWindow.pdf
- https://www.cityofboise.org/media/3924/434-irc-code-section-r305-ceiling-height.pdf
- https://shop.iccsafe.org/media/wysiwyg/material/7100S15-Sample.pdf
- https://www.nar.realtor/node/194378