Home Additions in Commerce City, CO

A home addition in Commerce City has to satisfy two sets of rules at once: the building code enforced by the Building Safety Division and the city’s zoning code, which was rewritten in 2025. Before anyone draws a wall, we confirm how the lot is zoned, what the setbacks allow, and whether any overlay applies. Then we design the addition to the structural and energy numbers the city publishes and file it through eTRAKiT.

Zoning First: The 2025 Land Development Code

Commerce City adopted a new Land Development Code on November 3, 2025. The city says it is working through the end of 2026 on a legislative rezoning effort to bring existing properties under the new code. That means a lot’s zoning, and which dimensional standards apply to it, may still be changing, so we confirm the current zoning with the city’s Property Lookup tool and the Planning Division before design.

Under the new code, the Single-Unit Dwelling building type sets a front setback of 15 feet, side setbacks of 5 feet, a 10-foot street-side setback on corner lots, and a 20-foot rear setback. Building coverage is capped at 45 percent of the lot, and height is capped at 35 feet. Alley-loaded homes use a different table, with a 10-foot rear setback and 60 percent coverage.

Where a lot is zoned as a planned unit development, the new code says that when an approved PUD zone document conflicts with the code, the PUD document controls. The city also reminds owners to check HOA restrictions. For a PUD lot, we pull the zone document and any HOA rules before we size the addition.

Floodplain and Other Overlays

Commerce City maps a Floodplain Overlay District that covers FEMA flood hazard areas and approved Mile High Flood District studies. The code says no construction, development, or storage of materials may begin in that district until a Floodplain Development Permit is issued by the city, and the Floodplain Administrator can require an engineer- or architect-certified floodproofing plan.

Within that overlay, new residential buildings are prohibited, and new construction or substantial improvements must be anchored, built with flood-resistant materials, and have mechanical and electrical equipment designed or located to keep water out. We check the flood maps for every addition lot before design starts.

The zoning code also bars new residential uses inside an airport noise contour of 55 DNL or higher. It does not say how that applies to an addition on an existing home, so on an affected lot we confirm with Planning before drawing.

The Permit and What the City Wants to See

Additions use the Residential Addition (RADD) permit, the same type the city uses for decks, garages, patio covers, and sunrooms. The submission includes building plans, a site plan showing the construction and landscaping, evaluation reports for unique products, a RESCheck printout if the design does not use prescriptive energy measures, and a construction cost breakdown covering materials and labor.

The plan checklist is specific: foundation and footing design, slab thickness with gravel base and vapor barrier, crawl space vents and access, floor and roof framing, braced wall lines, a wall section, elevations, insulation and window values, alarm locations, and building height, which the city caps at 35 feet from grade to roof midpoint.

Commerce City does not generally require sealed drawings for homes designed under the residential code, but the building official can require them. Soils reports appear on the city’s list of submission documents when applicable. We bring in an engineer where the foundation, a beam, or the soil calls for one.

Structural Numbers Set by the City

The city’s residential code table sets a ground snow load of 35 pounds per square foot, raised from 30 under the previous code, along with a 115 mph design wind speed, Seismic Design Category B, and a frost depth of 36 inches. Footings and roof framing for an addition are sized to those numbers, and the roof needs ice barrier underlayment.

Fire separation is measured from the finished face of the exterior wall. A detached single-family home needs sprinklers only where the fire separation distance is under 8 feet, and additions to existing townhouses without sprinklers do not trigger them. On a tight side yard, a few inches of siding can change the answer, so we measure carefully.

Energy Rules for New Square Footage

Commerce City is in Climate Zone 5. Its energy guidance for additions lists ceilings at R-49, wood-framed walls at R-20, floors at R-30, and windows and doors at U-0.30. Those values go on the drawings, or a RESCheck compliance certificate is uploaded instead.

The city allowed applicants to choose the 2018 or 2021 energy provisions until July 1, 2026. After that date all applicants must comply with the 2021 provisions, in line with state law HB22-1362. Because that change is recent, we confirm the current energy requirements with the office before submitting.

How We Sequence a Commerce City Home Addition

We start with the lot: zoning under the current code, any PUD document or HOA rules, flood maps, and the setbacks and coverage the addition must fit within. With that settled, we design the structure to the city’s snow, wind, and frost numbers, add engineering where needed, and assemble the RADD submission. Commerce City lists a Class C license for work on one- and two-family dwellings, with a $60 fee and an ICC exam or reciprocal license, and the application goes in under the contractor’s licensed eTRAKiT account.

Residential plan review is published at 14 days from the completeness review, with 7 days for each follow-up. Once the permit is issued, excavation is fenced as the city requires, and inspections are booked in eTRAKiT by 4 p.m. the business day before. Foundation, framing, rough trades, insulation, and finishes follow, and the final inspection closes the permit.

Common Questions

What setbacks apply to a home addition in Commerce City?
Under the 2025 Land Development Code, the Single-Unit Dwelling type sets a 15-foot front, 5-foot side, 10-foot corner, and 20-foot rear setback, with 45 percent maximum coverage. The city is rezoning existing properties through the end of 2026 and PUD documents can control, so confirm your lot’s zoning with the city.

How tall can my addition be?
The city’s additions guidance caps building height at 35 feet, measured from grade to the roof midpoint. The new zoning code also lists 35 feet for the Single-Unit Dwelling type.

Do I need a floodplain permit for an addition?
If the lot is in the Floodplain Overlay District, no construction may begin until the city issues a Floodplain Development Permit. The Floodplain Administrator may require a certified floodproofing plan.

Which energy code applies to a new addition?
The city allowed a choice of the 2018 or 2021 energy provisions until July 1, 2026, after which all applicants must comply with the 2021 provisions. Confirm current requirements with the Building Safety Division.

Talk to Us About Your Project

Tell us what the addition needs to hold, whether that is a bedroom suite, a larger kitchen, or a family room. We check your lot’s zoning, overlays, and setbacks, design to Commerce City’s structural and energy numbers, and manage the permit and inspections from foundation to final.