Egress Window Permit Checklist: Denver Metro
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Before you add or enlarge a basement egress window in the Denver metro, confirm the room needs egress, check the window and well against the IRC minimums, find the code your city uses, and get the permit from your building department.
Informational only. This checklist summarizes public code text. Your building department has the final word.
Step 1: Do you need egress?
- Is the basement room used, or will it be used, for sleeping? Under IRC R310.1, every sleeping room and every basement with habitable space needs at least one operable emergency escape and rescue opening (EERO). Source: 2021 IRC R310.1.
- Centennial: a room counts as a sleeping room if it meets R304/R305 dimensions and has a closet, a closet-usable area, or space readily convertible to one (Centennial Ord. 2023-O-06).
Step 2: Check the window
Section R310 in the 2021 IRC; R319 in Denver's 2025 code (2025 Denver Building Code).
- Net clear opening of at least 5.7 sq ft
- Net clear height of at least 24 in.
- Net clear width of at least 20 in.
- Sill no more than 44 in. above the floor
- Denver existing and replacement windows: an existing operable window may serve at 4 sq ft net clear / 22 in. high / 20 in. wide (2025 DRC R319.5 item 3). Replacements follow R319.5 (BO104.8.3). For a change of occupancy, a replacement at that size that is the largest standard size fitting the existing opening is also accepted (BO108.8.3).
- Douglas County / Highlands Ranch: replacement windows are permit-exempt when the rough opening doesn't change structurally and the style is the same or opens equal or larger. Source: Douglas Co. amendment R105.2(13).
Not sure about your window? Try the egress window check.
Step 3: Check the well
- Well area of at least 9 sq ft
- Horizontal projection and width each at least 36 in.
- The window can open fully inside the well
- Deeper than 44 in.? A ladder is required, and it can't encroach more than 6 in. into the required dimensions (2021 IRC R310.2.3.1)
- Douglas County / Highlands Ranch: existing R-3 basements may use a 24 in. minimum projection (full window width). A ladder must not obstruct the operable side. Source: Douglas Co. amendment R310.4.1 Exc. 2.
Step 4: Which code applies
| Where | Code in effect (Oct 2026) |
|---|---|
| Denver | 2024 IRC (2025 Denver Building Code, eff. 12/31/2025) |
| Aurora | 2021 IRC |
| Lakewood | 2021 IRC |
| Arvada | 2024 IRC (from 7/1/2026) |
| Thornton | 2024 IRC (from 7/1/2026) |
| Centennial | 2021 IRC |
| Littleton | 2024 IRC |
| Englewood | 2024 IRC (permits after 5/31/2026) |
| Douglas Co. / Highlands Ranch | 2021 IRC |
| Unincorp. Arapahoe | 2021 IRC |
| Unincorp. Jefferson | 2024 IRC (applied 7/1/2026+) |
| Unincorp. Adams | 2024 IRC (applied 7/1/2026+) |
For other cities and the permit office for your address, see the permit guide.
Step 5: Denver application notes
- Adding or enlarging a window opening needs a permit. Apply in e-permits: Development Services, then Apply for a Permit, then Building Log (CPD Residential Interior Remodel).
Step 6: Permit fees
Each office sets its own fees. Check the official page for your address:
| Where | Official fee page |
|---|---|
| Denver | Development fees |
| Aurora | Permit fee calculator |
| Lakewood | Fee schedule |
| Arvada | Building fee schedule |
| Westminster | Fee schedule |
| Thornton | Building permit fee schedule |
| Centennial | Building permit fee schedule |
| Littleton | Permit fee schedules |
| Douglas Co. / Highlands Ranch | Building fees |
| Unincorp. Jefferson | Fees |
| Unincorp. Adams | Permit fees |
Related
Guides: Basement bedroom egress · Permit guide · Egress code guide · Egress window check Services: Egress window installation · Window well installation · Basement egress cutting
Frequently asked questions
Do I need a permit to add an egress window in Denver?
Yes. Denver CPD says adding or enlarging a window opening needs a permit, applied for through e-permits.
Where do I find permit fees?
Each office sets its own fees. Step 6 links each city's and county's official fee page.