Basement Finishing in Commerce City, CO

Finishing a basement in Commerce City starts with a permit. The city lists interior alterations, including finished basements, as permit work, and it publishes its own Typical Basement Finish Details guide that inspectors expect to see on site. Our crew builds Commerce City basements to that guide from framing to final, so the space passes inspection the first time and stays comfortable once the family moves in.

The Permit and the City’s Basement Guide

Basement finishes use the Residential Alteration (RALT) permit, filed electronically through eTRAKiT. The city’s basement page asks for building plans, window-well specifications when a manufactured well is used, evaluation reports for unique products, and the Basement Finish Guide. Plans must show egress, smoke and CO alarm locations, fireblocking, under-stair protection, combustion air, ceiling heights, the room layout with the furnace, water heater, and panel, and bathroom fixture clearances.

The current guide is Version 2021.0, dated May 18, 2023, and based on the 2021 International Residential Code. It says construction cannot deviate from its details without prior approval, and a copy must be on the job site at every inspection. Because the guide carries a date, we check with the Building Safety Division for any newer version before we submit.

The guide also flags three things that always need a plan submission and city approval: a basement that includes a kitchen, wet bar, or bedroom; cutting a new opening in an existing basement wall; and adding a new window well. Plan review for residential work is published at 14 days from the completeness review, with 7 days for each follow-up.

Bedrooms, Egress Windows, and Window Wells

Every new basement bedroom needs an emergency escape and rescue opening. The city notes that homes built after 2003 already had one installed. An older home can finish its basement without one if no bedroom is added, though the city strongly recommends it. The opening must be at least 5.7 square feet, or 5.0 square feet at a walkout, with at least 24 inches of height, 20 inches of width, and a sill no higher than 44 inches.

The escape opening must lead along a 36-inch clear path to a street, alley, or yard at least 10 feet wide, and one under a deck or porch needs a 36 by 36 inch clear path. It has to open from inside without a key or tool.

Window wells need at least 9 square feet of clear floor area with the window open and at least 36 inches in each direction. Wells deeper than 44 inches need a permanent ladder or steps at least 12 inches wide. Wells deeper than 30 inches need a cover or grate rated for 40 pounds per square foot, a rule the city added with the 2021 code. Wells drain to the foundation drain or to daylight, or else get No. 57 stone.

Ceilings, Room Sizes, and Stairs

Ceilings must be at least 7 feet high. Beams, girders, ducts, and similar obstructions may drop to 6 feet 4 inches. Habitable rooms need at least 70 square feet and must measure at least 7 feet in any direction, and hallways must be at least 36 inches wide.

Those numbers decide the floor plan. We map the ductwork and beams first, then place bedrooms and the family room where the ceiling height works and tuck storage and the mechanical room under the lowest runs.

At the stair, the city requires a light switched at the top and bottom, and any usable space under the stair gets half-inch drywall. Floors with an unfinished underside may also need a half-inch gypsum membrane under the 2021 code, with exceptions such as 2×10 or larger dimension lumber floors.

Alarms, Insulation, and Floating Walls

The guide calls for a smoke alarm in the basement, on each floor, in each bedroom, and outside sleeping areas, kept at least 3 feet from a bathroom door with a tub or shower. Where gas appliances are present, CO alarms go within 15 feet of them and on every floor. All alarms are interconnected, and basement alarms are hardwired with battery backup.

Basement walls should be insulated with continuous R-15, or R-19 when the insulation sits between studs, and R-19 requires 2×6 studs. Bottom plates on concrete are preservative-treated, and vertical fireblocking runs no more than 10 feet apart.

Commerce City recommends floating partitions where expansive soils can heave the slab, with a gap of 1½ to 3 inches, and requires the float at the top of walls around a shower. Plans must show those details, so we draw them before framing starts.

Mechanical Room, Panel, and Circuits

Furnaces and water heaters need a 30 by 30 inch clear space at their controls. When they sit in a closed room, combustion air openings are sized at 1 square inch per 1,000 Btu per hour, at least 100 square inches each, unless a louvered door or a large room volume covers it.

The electrical panel needs a clear workspace 30 inches wide, 36 inches deep, and 6.5 feet high, and it cannot sit in a closet or bathroom. Each unfinished area needs at least one GFCI outlet, laundry gets a dedicated 20-amp circuit, and branch circuits use combination arc-fault breakers. The city enforces the 2023 National Electrical Code for permits applied for after August 1, 2023.

Radon comes up often in basement planning. Commerce City’s code adoption list does not include the radon appendix, and neither the basement guide nor the basement page states a radon requirement. We point homeowners to the city to confirm before deciding whether to add mitigation.

How We Sequence a Commerce City Basement Finish

We start by measuring ceiling heights, existing windows, and the mechanical room against the city’s guide, then draw a plan that shows every item the basement page asks for. If a bedroom, wet bar, new window well, or new wall opening is involved, it goes in the submission. We file the RALT permit in eTRAKiT and keep the guide on site once work begins.

Framing, fireblocking, rough plumbing, and rough electrical come first, followed by rough-in inspections booked in eTRAKiT by 4 p.m. the business day before. If an egress window means digging, the open excavation gets the 6-foot fence the city requires. Insulation, drywall, finishes, and alarms follow, and the final inspections close the permit.

Common Questions

Do I need a permit to finish my basement in Commerce City?
Yes. Commerce City lists interior alterations, including finished basements, as work that requires a permit. Basement finishes use the Residential Alteration (RALT) permit and are submitted electronically.

Does my basement need an egress window?
Each bedroom you add needs an emergency escape and rescue opening. The city notes that homes built after 2003 already have one, and older homes may finish without one if no bedroom is added, though the city strongly recommends it.

How high does a finished basement ceiling have to be?
The city’s guide requires at least 7 feet, with beams, girders, ducts, and similar obstructions allowed to project down to 6 feet 4 inches.

Does Commerce City require radon mitigation in a basement finish?
No radon requirement appears on the city’s basement page or in its basement guide, and the radon appendix is not on the city’s list of adopted appendices. Confirm with the Building Safety Division before you decide.

Talk to Us About Your Project

Tell us how you want to use your basement, whether that means bedrooms, a bathroom, a wet bar, or a family room. We measure the space against Commerce City’s basement guide, prepare the plans and permit, and build through the rough and final inspections.