Do I Need a Building Permit in Colorado?
Colorado building permit rules. No statewide code edition, an energy code that attaches to having any building code at all, plumbing inspection split between the state and local programs, and an ADU mandate bounded by three separate gates.
Almost certainly yes, but Colorado does not answer it at the state level. There is no single statewide building code edition; each city or county adopts its own, so the permit requirement and the code edition you build to are both local. State law does set a floor in three specific places: an energy code, who inspects plumbing and electrical work, and — in some jurisdictions only — a right to build one accessory dwelling unit.
There is no statewide code edition, and the energy statute assumes it
Colorado does not publish one building code edition that every jurisdiction must enforce. Which code your project is built to is set by your city or county, so two addresses twenty minutes apart can be on different editions. You do not have to take that on trust — the legislature wrote the assumption into its own energy-code statute. C.R.S. 31-15-602(3), as amended by HB22-1362, addresses itself to a municipality “that has adopted and enforced one or more building codes, or that adopts and enforces one or more building codes after July 1, 2022”, and C.R.S. 30-28-211(3) uses the same construction for a board of county commissioners. Language conditioned on whether a jurisdiction has a building code only makes sense if state law accepts that some do not. So the first question is not what Colorado’s building code is — there is no such single thing to look up — but whether your own jurisdiction enforces one, and which edition it is on. (House Bill 22-1362 as signed, read from the enrolled act on 10 September 2026.)
The energy code attaches to having a code at all, not to updating one
This is the part that is easy to get backwards. The duty to enforce an energy code does not wait until a jurisdiction updates its building code — it attaches as soon as the jurisdiction has one. Under C.R.S. 31-15-602(3) a municipality that has adopted and enforced one or more building codes, or that adopts and enforces them after July 1, 2022, “shall adopt and enforce an energy code that applies to the construction of, and major renovations and additions to, all commercial and residential buildings as required by the energy code in the municipality to which the building code applies”. What updating changes is which edition you must meet. Under C.R.S. 31-15-602(3.5)(a) a municipality that updates one or more building codes on or after July 1, 2023 and before July 1, 2026 must adopt an energy code achieving “equivalent or better energy performance than the 2021 international energy conservation code and the model electric ready and solar ready code language” developed by the state energy code board; under (3.5)(b), updating on or after July 1, 2026 raises that to the model low energy and carbon code. C.R.S. 30-28-211 carries the parallel rules for counties. The practical consequence: a jurisdiction with no building code at all is not pulled in by this statute, and one that has never updated since 2022 still owes an energy code, just not necessarily the 2021 IECC tier.
Whether the state or your city inspects plumbing is an either-or, not a layer
Plumbing and electrical permitting in Colorado default to the state boards inside the Division of Professions and Occupations, but that default switches off wherever a local programme exists. The Division states that “the State does not inspect in local jurisdictions having its own Plumbing Inspection Program”, adds that “you are responsible for determining the correct inspection authority”, and publishes a county-by-county list of the local jurisdictions to approach instead. Read that as mutually exclusive rather than layered: for a water heater, a panel change or a repipe, one authority has your job and the other does not, and applying to the wrong one wastes the fee and the wait. Check your address against the Division’s local inspection-area list before you apply. (Colorado Division of Professions and Occupations, Electrical and Plumbing Permits, read on 9 September 2026.)
The ADU mandate is real, and it stops at three separate gates
Colorado now requires some jurisdictions to allow an accessory dwelling unit, and the requirement is mandatory language, not encouragement. C.R.S. 29-35-103(1) reads: “On or after June 30, 2025, a subject jurisdiction shall allow, subject to an administrative approval process, one accessory dwelling unit as an accessory use to a single-unit detached dwelling in any part of the subject jurisdiction where the jurisdiction allows single-unit detached dwellings.” Three gates decide whether that sentence reaches you. First, your jurisdiction must be a subject jurisdiction, defined at C.R.S. 29-35-102 as “either: (a) a municipality that both has a population of one thousand or more, as reported by the state demography office, and is within a metropolitan planning organization; or (b) the portion of a county that is both within a census designated place with a population of forty thousand or more, as reported in the most recent decennial census, and within a metropolitan planning organization.” Both halves must be true, so a town of 4,000 outside every metropolitan planning organization is not covered. Second, C.R.S. 29-35-103(4) provides that “this section only applies to a parcel in a subject jurisdiction that is not an exempt parcel”, and an exempt parcel under C.R.S. 29-35-102 is one “not served by a domestic water and sewage treatment system” or “served by a well with a permit that cannot supply an additional dwelling unit”, a historic property outside a historic district, or land in a floodway or a one-hundred-year floodplain. Third, the right only reaches parts of the jurisdiction where detached homes are already allowed. Outside those three gates the answer returns to ordinary local zoning.
What a covered jurisdiction may no longer do — and how the state reached home-rule cities
Where the mandate does apply, C.R.S. 29-35-103(2) removes three familiar obstacles: a subject jurisdiction may not require a new off-street parking space for the ADU except in the narrow cases the statute spells out, may not require the ADU or another dwelling on the lot to be owner-occupied except when checking residence at application, and may not apply a restrictive design or dimension standard. It may still do plenty. C.R.S. 29-35-103(3) preserves a long list of local powers, including — worth knowing before you apply — “requiring a statement by a water or wastewater service provider regarding its capacity to service the property as a condition of permitting an accessory dwelling unit”, and setting a size range so that an ADU is no smaller than five hundred square feet, no larger than eight hundred, or no larger than the principal dwelling. Two further reaches are easy to miss: a homeowners association provision restricting an ADU in the way the statute forbids is “void as a matter of public policy”, and C.R.S. 24-67-105(5.3) stops a planned unit development from restricting ADUs more tightly than the local law applying outside the PUD. The reason any of this binds Colorado’s home-rule cities, which normally win on matters of local concern, is that the statute defines “municipality” to mean “a home rule or statutory city or town, territorial charter city or town, or city and county”, and the general assembly expressly declared ADUs “a matter of mixed statewide and local concern”. That declaration is the hinge, and it is why a home-rule charter is not by itself an answer here.
Ask your city or county, because in Colorado that is genuinely where the answer lives — there is no statewide building code edition to look up, and the permit requirement travels with the local code rather than with state law. Three things do come from the state and are worth checking before you apply. Your jurisdiction owes an energy code if it enforces any building code at all, with the required edition rising when it updates. Plumbing and electrical inspection belongs either to the state Division of Professions and Occupations or to a local programme, never to both, and applying to the wrong one costs you the fee. And if your address sits in a subject jurisdiction on a parcel that is not exempt, you have had a statutory right to one accessory dwelling unit since 30 June 2025 that no design standard, owner-occupancy rule or HOA covenant can quietly take away.
Based on the International Residential Code (IRC) and International Building Code (IBC) model codes. Every jurisdiction adopts a specific edition with its own local amendments — check your city’s permit page for the exact codes in force and their source citations.