Egress window code in Fort Collins and Northern Colorado: the reference page

This page is the code behind every other page on this site. It covers the IRC Section R310 numbers, the edition Fort Collins enforces, the city’s own additions that catch homeowners and out-of-town contractors, the historic chart the city uses to judge older windows, what turns an opening into a legal bedroom, and which office permits each town we serve. Everything here is read from the city’s and county’s own publications, and the permits and inspections page covers how we handle the paperwork.

The edition in force

The City of Fort Collins adopted the 2024 International Codes with local amendments for any permit submitted on or after April 1, 2026: the 2024 International Building, Residential, Energy Conservation, Mechanical, Fuel Gas, Plumbing, Existing Building, Property Maintenance, and Swimming Pool and Spa Codes. The 2021 editions, which the city applied from April 15, 2022, remain available for reference until October 1, 2026. The city’s published design values that matter for this work are a 30 inch frost depth and a default residential ground snow load of 35 psf.

Unincorporated Larimer County adopted its own 2024 codes on September 22, 2025, effective January 1, 2026, with the same 2024 IRC and a countywide minimum frost depth of 30 inches below grade.

IRC R310: the dimensions

An emergency escape and rescue opening is required in basements, habitable attics, and every sleeping room. One numbering note before the table: the 2021 IRC carries these rules as Section R310, with the well rules at R310.4, and the 2024 IRC moved the whole section to R319 without changing a figure, so R310 in the 2024 book is smoke alarms. Inspectors, the city’s guides, and every window catalog still say R310, and so does this site. For a window to qualify:

“Net clear opening” means the hole a person can climb through with the window fully open, not the glass size and not the rough opening. A 24 by 20 inch opening is only 3.3 square feet; you cannot hit 5.7 at both minimums, which is why real egress units are meaningfully larger in one dimension. The egress window installation page shows how we size backward from the number.

What Fort Collins adds

The city’s Emergency Escape and Rescue Windows guide and its Residential Basement Finish Guide restate the IRC numbers and then add requirements of their own:

• An engineer’s letter for foundation openings. “For new or altered windows in foundation walls: submit a letter or drawings evaluated/designed and stamped by a Colorado Licensed Engineer.” For windows in load-bearing wood-framed walls, the new header size has to be on the application.
• Drainage to the foundation drain. New window well installations “shall be designed for drainage and connected to the building’s foundation drain (if present).” On the clay under this city that is not a formality; see well covers and drainage.
• A clear path to the public way. New wells need an unobstructed route to the sidewalk or street. Wells in a series may use a metal grate cover, and a gate in a fence is permissible.
• Fall protection. Required for new wells adjacent to doors and walking surfaces. The city’s rental standards go further for landlords: guardrails or grate covers on any well within 3 feet of a driveway or sidewalk.
• Replacement windows. A replacement in an existing egress opening must keep the same operation and the same clear opening or larger, and never less than 22 inches high, 20 inches wide, and 4 square feet.
• Window performance. New and replaced windows in a basement finish are labeled to a maximum U-factor of 0.28 and a maximum SHGC of 0.35.

The historic chart: what your house was built to

The city keeps a chart of its own egress requirements by adoption date, and it says that “windows installed/built under older codes are still considered code compliant.” That chart decides a lot of inspection arguments in this town.

Three practical readings of that chart. A basement bedroom in a house permitted in 1974 can be legal with a 5 square foot window and a 48 inch sill, and a buyer’s inspector will still call it small. A house from the 1980s or early 1990s was built to today’s window numbers but was never required to have a 36 inch well, so its well may be too small for a person to climb out of even though the window passes. And anything finished without a permit, or any bedroom being created now, is judged by the current numbers. The failed inspection page turns the chart into a five-minute check.

What makes the room a bedroom

The city’s guide says it in bold: the installation of an emergency escape and rescue window does not create a legal bedroom. A remodel permit or a basement finish permit is required to create or relocate a bedroom. The city’s basement finish checklist, revised for the 2024 codes, sets the rest of the bar:

• An emergency escape and rescue opening in every bedroom; a basement with no bedroom needs one opening, door or window.
• Minimum bedroom size 70 square feet and not less than 7 feet in any direction.
• Minimum ceiling height 6 feet 8 inches in bedrooms, living areas, and hallways; 6 feet 4 inches in showers, storage, laundry, and under ducts and beams.
• Smoke alarms inside and outside sleeping areas and on every level; a carbon monoxide alarm within 15 feet of the bedroom.
• Uninsulated foundation walls insulated to R-19 continuous, R-13 plus R-5 continuous, or R-19 between studs.
• Pressure-treated bottom plates on concrete; floating walls allowed but not required.
• Inspections: rough frame, electrical, plumbing, and mechanical; insulation before drywall; finals.

The basement finish permit itself is a flat $155 fast-track permit in Fort Collins. The egress opening is permitted by valuation: $105 up to $2,000 of work, then $15.50 per additional $1,000 up to $25,000, which puts most egress jobs at $150 to $300. Both are itemized at cost on our quotes. The basement bedroom conversion page is the version of this job that carries the room all the way to a permitted bedroom.

Licensing

Fort Collins requires a city contractor license of every contractor working inside the city, with license classes that include D1 for single-family work and E(R) for nonstructural residential alterations, and it lists the classes allowed to finish basements. Colorado does not issue a statewide general contractor license; the state licenses plumbers and electricians, and each city or county licenses builders. That is why this site says “licensed, insured local installers” and never prints a license number: there is no state number to print, and the city license is what an inspector checks.

Who permits each town

Your address decides the office, not your mailing city. The IRC R310 dimensions are the same model-code numbers everywhere in Northern Colorado; what changes is the edition in force, the local amendments, the fee, and who inspects.

We file with the office that covers your parcel, pass the fee through at cost, and schedule the inspections as part of the job. If you are not sure which side of a line your house sits on, send the address with the form and we will tell you before anyone quotes.

The honest caution

Nobody can guarantee a permit approval, an inspection pass, or an appraisal outcome, and this page is a reference, not the code itself. The city’s guides and the adopted amendments are the documents an inspector works from, and when they change, the local code wins. What we can promise is that the work is built to IRC R310 and the local amendments, the engineer’s letter and the permit are handled end to end, and the inspection is part of the job. The pricing page shows what each line costs.