Building permits, zoning and septic rules in Jefferson County, Colorado

Every new home or dwelling unit in unincorporated Jefferson County requires a building permit, as does structural construction and other covered work¹. Replacing cabinets, flooring or counters in the same general locations may not require a building permit; ask Building Safety to confirm the scope¹. Jefferson County’s 2024 Building Codes and Supplements and updated wildfire regulations apply to building permit applications filed on or after July 1, 2026, and only in unincorporated Jefferson County¹¹. County-permitted work must remain accessible and exposed until approved at the required inspection¹². Municipal building offices handle building permits inside Lakewood¹³, Arvada¹⁴, Westminster¹⁵, Wheat Ridge¹⁶, Golden¹⁷, Town of Superior (mainly in Boulder County, reaching into Jefferson County)¹⁸. Jefferson County Public Health remains the septic authority for addresses in Jefferson County, including city addresses⁵.

Jefferson County Building Safety handles building, electrical, mechanical and plumbing permits, plan review and inspections for unincorporated property¹¹. Building Safety is at 100 Jefferson County Parkway, Suite 3540, Golden; call 303-271-8260¹¹. Engineered truss drawings and layout documents must accompany the initial county building permit application, and plan-review appointments are available in person or virtually¹¹. County inspection requests must arrive by 5 p.m. the day before inspection¹¹. When a certificate of occupancy applies, final building inspection is followed by final review; outstanding Planning & Zoning or Public Health items can delay issuance¹⁹.

Jefferson County zoning applies to unincorporated land under the resolution effective July 1, 2026⁶. Published districts include Residential, Mountain Residential, Suburban Residential, Agricultural and Mobile Home Park; Planned Development parcels have site-specific standards^2,20. Minimum lot size, height and setbacks depend on the district, with setbacks also varying by structure type^1,10,21. Easements, floodplain, wildfire-interface and access requirements may further constrain the building site; ask Planning & Zoning to identify the parcel’s district and overlays before designing^1,20. Municipal zoning applies inside Lakewood²², Arvada²³, Westminster²⁴, Wheat Ridge²⁵, Golden²⁶, Edgewater²⁷, Mountain View²⁸, Morrison²⁹, Superior (mainly in Boulder County, reaching into Jefferson County)³⁰. Jefferson County Public Health retains septic authority for the Jefferson County portions of these municipalities⁵.

Jefferson County Public Health regulates onsite wastewater treatment systems, commonly called septic systems, throughout Jefferson County; this county role does not move to a city when an address is incorporated⁵. Property owners may need a county septic permit to install a new system, repair or replace one, or make changes that affect it⁵. For a building without sewer service, Colorado requires the OWTS permit before building approval and a final OWTS inspection before occupancy approval³¹. Before the sale of a property whose system was installed more than 5 years earlier, the owner must have the system inspected and obtain a use permit³². Only about 5.3% of county soils lack severe limitations for a conventional drain field, so septic feasibility deserves an early site evaluation³³. Reach Environmental Health Services at 303-232-6301³⁴.

Camping is limited to 2 weeks per year in most Jefferson County zoning districts, but the county material does not identify every district exception³⁵. We could not confirm a separate rule allowing long-term residential RV occupancy, so ask Planning & Zoning about the parcel, vehicle and proposed duration before treating an RV as housing²⁰. Colorado-regulated tiny homes can be approved for long-term living only after Division of Housing plan approval, and the unit must still satisfy local zoning and applicable codes⁸. A HUD-code manufactured home may be installed only where local zoning allows it, with state installation rules and local foundation or structural requirements still applying⁸. Jefferson County's exact minimum dwelling size was not confirmed, so ask Planning & Zoning rather than assuming a small footprint is allowed²⁰.

1. For unincorporated land, ask Planning & Zoning to confirm the zoning district, allowed use, setbacks, height and minimum lot size; inside city limits, obtain zoning requirements from the municipality^1,2,10.
2. Confirm that the parcel is a legal division of land eligible for a building permit¹⁰.
3. Establish compliant legal and physical access before applying for the building permit¹⁰.
4. Secure a state well permit if groundwater will supply the home; an accessory dwelling also needs documentation that the well can serve multiple dwellings^9,36.
5. If the home lacks sewer service, obtain the Jefferson County OWTS permit before building approval, even for an address inside a city^5,31.
6. For unincorporated land, apply to Building Safety with the required plans and truss documents; for land inside a city, contact the municipality for its building permit process^3,11.
7. Under the contractor-license exemption, an owner-builder may obtain a building permit for one dwelling in a 24-month period for personal use and occupancy⁷.
8. Keep county-permitted work exposed for required inspections; when a certificate of occupancy applies, complete final review and resolve any outstanding Planning & Zoning or Public Health items^11,19.

For unincorporated land, start with the county zoning map and district rules because allowed uses, lot size, setbacks and height can change by district; for land inside city limits, obtain zoning from the municipality^1,2,10,20. Only about 5.3% of Jefferson County soils lack severe limitations for a conventional drain field, so do not assume a standard system will work³³. Only 38.6% of county land has a slope of 15% or less, and 69.2% is wooded, making the actual building envelope and access important to inspect³³. Confirm legal access before closing because a new home on unincorporated land must meet county access requirements before its building permit can issue¹⁰. Direct access to a state highway separately requires a state access permit³⁷. Verify subdivision status, water supply and whether any county floodplain, geologic-hazard or wildfire overlay affects the parcel before committing to a design^10,20.