Housing Choice Code Amendment
The City is hosting an Open House for the Housing Choice Code discussion on March 4, 2026 from 4:30 pm to 7:30 pm at the Trail Winds Recreation Center. Please stop by and share your thoughts on Housing in the City of Thornton!
Thornton's City Development Department has kicked off the Housing Choice Code Amendment. This project focuses on exploring the tools available to increase housing choice in the city and meeting local housing goals. Fill out the survey and find more information on the Housing Choice Code Website.
Development Code Update
If resubmittals on pending applications are not filed by February 12, 2026, the applicant must file a new application with the city and that application will be subject to the new Development Code as adopted by Council.
Planner of the Day (POD)
Current Planning Division has a Current Planner available to the public daily, providing fast and accurate customer service. The Planner of the Day can provide general zoning, process and development information. You can contact Current Planning during business hours to reach the Planner of the Day.
Email the Planner of the Day
Development Submittal Information
The Current Planning Division at the City of Thornton is charged with overseeing and controlling development within the City. This is accomplished through reviewing and providing recommendations on: applications for Annexation, Rezoning and Subdivision of land, Conceptual Site Plans (CSPs), Temporary Use Permits (TUPs), proposed architecture for new buildings and additions, building permits, and minor amendments to approved projects.
Helpful Resources for Homeowners
What is an ADU?
An ADU is a second dwelling unit that is on the same property as a single-family detached dwelling (primary residence). The property owner must live in either the primary residence or the ADU. An ADU comes in three forms:
- Detached – a detached unit from the existing house located on the same lot.
- Attached – an attached unit (addition) to the existing house located on the same lot.
- Within the primary residence – a unit that is integrated into the existing house.
To be considered an ADU, the space must contain: a living area, sleeping facilities, a bathroom, and a kitchen with a stove. A kitchen will be assumed if 220V wiring is proposed. ADUs are allowed for single-family detached dwellings in most residential zone districts. Contact the Planning Department to see if your property qualifies.
Use Standards for ADUsWhat permits are required for an ADU?
- An ADU will always require either a Major Development Permit or Minor Development Permit, depending on the size of the project. Consult with a city planner to determine which type of permit will be required.
- A building permit will be required once the Major Development Permit/Minor Development Permit is issued. Please contact the Building Inspection Division for more information regarding the building permit requirements at 303-538-7250.
- A deed restriction is required by the City for an ADU prior to the issuance of a building permit.
ADU Development Standards:
Size:
- Minimum Unit Size: 500 square feet
- Maximum Unit Size: 1,000 square feet or 50% of the gross floor area of the primary dwelling, whichever is greater.
- When calculating the maximum size of an ADU, gross floor area of the primary residence does not include any garage, porch, or similar area.
Parking:
- Minimum Off-street Parking Spaces: 1 off-street parking space required + regular required parking (usually 5 total spaces required on site)
In addition to the size and parking requirements listed above, the ADU must meet all other development standards for the specified zone district listed in Article 3 of the Development Code, including height, setbacks, and design standards.
Water Service:
Adding additional plumbing fixtures to an existing water service should be evaluated before applying for a permit. Contact the Building Inspection Division for more information at 303-538-7250.
Sewer Service:
Separate connection fees are required by the Metro Wastewater District for an ADU. Fees are subject to change and may be higher depending on water meter size requirements. Contact the Utility Billing Department at 303-539-7370 to learn about current fee costs and to arrange for payment.
Decks and patios can be located in the front, side, and rear yards. A Building Permit is required for all decks, patio enclosures, and patio covers. Patios only consisting of flatwork do not require a building permit. Building Permits are issued through the Building Inspection Division. Current Planning reviews deck and patio permits for the following:
- Setbacks
- Utility Easements
- Height
- Compatibility with the existing structure (when located in the front yard)
- Lot Coverage
These regulations can differ depending on the zoning district of the property and if the deck is unenclosed or fully enclosed. Please contact the Planner of the Day for specific requirements.
For the full regulations on fences, please see Chapter 18, Article 6, Division 2
These regulations apply to most residential homes located in the Residential Low Density, Residential Mid Density, and Residential High Density Districts. Neighborhoods with the Planned Development Zoning District may have different fence guidelines. You can check what the zoning is for a property by looking at the Thornton Property and Zoning Information map. Contact pod.info@thorntonco.gov for help with Planned Development Districts.
What: Fence means any structure that is comprised of posts, boards, wire, stakes, rails or any combination of similar elements that provides a physical barrier, enclosure, or boundary. (This definition does not include golf safety nets as defined in this section and regulated in Section 18-349).
Where: Fences are allowed on or within the subject property lines. (Property line locations are not verified by the City of Thornton.)
- Fences over 2 ft. 6 in. in height are not allowed in visibility triangles. Visibility triangles are generally found on corner properties at intersections, and are designed to ensure a safe line-of-sight for vehicles moving through the intersection. Refer to for Chapter 18, Article 6, Division 6 for complete visibility triangle regulations.
- Fences parallel to each other must have at least a 5 ft. gap between them.
Type: There are many allowed types of fences, from wood or vinyl privacy fences, open-rail fences, to wrought-iron fences.
- Prohibited fence types: Chicken wire, deer, and other temporary fence materials are prohibited except for:
- Urban Garden uses meeting the standards of Section 18-357 if the fence is located around the garden perimeter, located fully within the interior side and/or rear yard, setback at least 5 feet from the property line, and a maximum of 6 feet high.
- Temporary fences are prohibited, except in connection with ongoing construction projects, street maintenance, or traffic and pedestrian control.
Height: The height of a fence is measured from grade to the top of the fence.
- In select locations (typically adjacent to an arterial street, regional thoroughfare, or interstate and with additional approvals) fences may be allowed up to 8 ft. tall.
- Fences located in the side and rear yard may be up to 6 ft. tall.
- Fences located in the front yard may be up to 4 ft. tall.
- Fences over 2 ft. 6 in. in height are not allowed in visibility triangles.
- Refer to for Chapter 18, Article 6, Division 6 for visibility triangle regulations.
Permits: Construction of a new fence 7 feet high or taller requires a building permit from the Building Inspection Division.
Permit Required
Residential driveway installations require a permit from Planning & Zoning. Any new or replacement driveway must comply with the Development Code [PDF/19.3MB]. Apply for a driveway permit through City View Portal.
For alterations or additions of driveways on a home site in manufactured home subdivisions, please use this site plan template [PDF/283KB] when uploading to the portal. You must include dimensions for all the listed site features, if applicable.
Primary Driveway Replacements and Additions
- Three feet maximum in front of the livable portion of a home for a walkway.
- Setbacks:
- No minimum setback is required behind the front plane of the house.
- Homes with a two or more car garage: minimum of 3 feet between the edge of the driveway and the side property line. This setback is only required between the front plane of the home and the Right-of-Way.
- Homes with a single car garage or without a garage: 12-inch minimum side setback. 6-inch curb or other design element required to direct drainage away from adjacent lot. This setback is only required between the front plane of the home and the Right-of-Way.
Secondary Driveways
- Secondary access on residential lots is only allowed if approved by a City Traffic Engineer.
- Width: 12 feet maximum at all points along the driveway.
- Setbacks:
- Secondary driveways require a minimum of 3 feet between the edge of a driveway and a side property line.
Driveway Construction
Any material which is used to park on or drive on with a vehicle is considered part of the driveway. Driveways shall consist of an all-weather and drainable material or one of the following:
- Concrete paving
- Hot mix asphalt paving which consists of a binder and surface course
- Three-quarter-inch or larger rock a minimum of three inches in depth
- A material which has equivalent characteristics
Other Rules
- Circular driveways are not permissible, unless specifically allowed for as part of the Planned Development (PD) Standards for a property.
- Corner lots shall not have a driveway closer than 20 feet to intersections containing local streets, and no closer than 30 feet to intersections containing a collector.
Helpful Resources for Businesses
Chapter 18, Article 11 of the Development Code outlines the allowed number, size, height, and other restrictions for the construction and maintenance of attached, freestanding, electronic, and temporary signs on private property. Visit our Sign Code and Permit Requirements page for more details.
Temporary Use Permits allow applicants to hold a temporary event in accordance with Chapter 18, Article 4, Division 11 of the Thornton City Code. Temporary Use Permits are reviewed by Planning and are approved for a specified length of time, subject to certain conditions and regulations.
Apply for a Temporary Use Permit using City View Portal(opens in new window). For assistance on applying, please review the PortalHelp Article on Temporary Use Permits.
Food trucks are licensed and regulated through our Sales and Use Tax department. Please visit their website for required licenses, inspections, and further information.
Helpful Resources for Developers
Pre-Application meetings are an informal step in the Land Use application process. The meeting provides the opportunity to discuss a land use proposal with City Staff and receive feedback prior to making a formal application submittal to the City. Often, these meetings provide helpful contacts, resources, and ideas to better prepare a formal submittal of a development application. How to request a Pre-application Meeting
Evidence of Good Faith Effort
Prairie Dog Relocation Information Handout [PDF/151KB]
In accordance with Section 6-36 of the City of Thornton Municipal Code, developers must show evidence of good faith efforts to relocate prairie dog colonies from a development site, including the results of those efforts. The City of Thornton considers a good faith effort to relocate prairie dogs to include, at a minimum, but not limited to, two of the following actions:
- Contacting private and public property owners in Adams County to request use of their land for prairie dog relocation.
- Examining other personal property holdings of the developer, or other persons not listed, for suitability for prairie dog relocation.
- Working with Colorado Parks and Wildlife and City Development staff to examine the possibility of including prairie dog colonies in the proposed development. (This option is possible only on a case-specific basis.)
- Contacting at least one or more prairie dog relocation organizations to attempt to schedule prairie dog relocation.
- Contacting a contractor to inquire into possibility of relocating the prairie dogs to a black- footed ferret farm or raptor rehabilitation center.
- Pursuing any other options known to the developer.
If good faith efforts reveal that relocation is possible, the developer may relocate the prairie dogs, in conformance with Colorado Parks and Wildlife regulations, from the land slated for development. If good faith efforts reveal that relocation is not feasible, the developer may dispose of the prairie dogs through extermination methods permitted by the Department of Agriculture. The City strongly encourages property owners to capture and relocate or capture and donate the prairie dogs to a raptor rehabilitation center or black footed ferret conservancy. The City strongly discourages the use of any extermination method other than USDA gas cartridges.
Development Application Process
Documentation of good faith efforts to relocate prairie dogs from land slated for development is required at multiple stages throughout the development process:
- At First Submittal – Developer required to indicate (by marking the correct box on the development application) whether prairie dogs currently inhabit the site in question.
- Prior to DP Approval – For Development Permits, the developer must submit a letter that serves as evidence of good faith efforts to relocate the prairie dogs. If a development project does not require a Development Permit, then the planner assigned to the project will determine the appropriate time for submission of the evidence of good faith effort.
- With Grading Permit Application – To receive a grading permit, the developer must submit a letter indicating actions taken to remove prairie dogs from the site.
Relocation Permit Application
In order to relocate prairie dogs, a permit is required from Colorado Parks and Wildlife (CPW). The process takes approximately 30 days and requires the applicant to identify the relocation site, the process through which the prairie dogs will be relocated and the relocation organization. Colorado Parks and Wildlife recommends that individuals who are attempting prairie dog relocation start by contacting a relocation organization.
State statutes prohibit the transfer of prairie dogs across county lines without the prior approval of the board of county commissioners of the receiving county. Developers may wish to approach public and private landowners in Adams County to search for relocation sites. In addition, developers may wish to review their existing property holdings or to purchase land to examine the possibility of relocating the prairie dogs to another site within Adams County.
CPW has guidelines as to what constitutes a suitable prairie dog relocation site. Contact CPW for specific guidelines at 303-291-7227.
Timing of Relocation
Prairie dogs can be relocated only at specific times during the year, which must be considered when planning relocation. While the relocation process must commence as early as possible in the development process to ensure success, prairie dogs must be physically relocated close to the time of grading to prevent recolonization prior to the start of construction.
Relocation Organizations
- Smith Environmental and Engineering
- Animal & Pest Control Specialist, Inc.
- Roe Ecological Services, LLC, 970-532-1305