Current Planning & Zoning

​​​​​​​​​​​​​​​​​​​​​​​​​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.

What 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.
  • Deed Restriction Template [PDF/284KB]

  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 smaller.
    • 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 V 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.

    Artificial Turf Regulations and Application Deck and Patio Information

    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.

    Residential Fence Information

    For the full regulations on fences, please see Chapter 18-565.

    These regulations apply to most residential homes located in the Singe-Family Detached, Single-Family Attached, and Multifamily Zoning District. 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 18-166.)

    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. Verify with City Development if you have a visibility triangle on your property.
    • Parallel fences 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: Fences constructed of chicken wire, wafer or particle board, or plywood are prohibited along any property line or in any required building setback where visible from a public street. Fences constructed of plastic netting or any types of plastic mesh 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 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.
      • Verify with City Development if you have a visibility triangle on your property.

      Permits: Construction of a new fence or the repair/replacement of an existing fence requires a building permit from the Building Inspection Division.

      Manufactured Home Site Plan

      Helpful Resources for Businesses

      Sign Permits

      Section 18, Article VII 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 Food Trucks

      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

      Development Summary Information Entitlements and Construction Development Process Development Review Guide Pre-application Meeting Information

      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.

      Scheduling a Pre-application Meeting:

      The following documents are required in order to schedule a pre-application meeting with City Staff:

      1. A Cover Letter: The cover letter should explain any anticipated uses, identify the number of units, provide the square-footage of the building, identify the types of businesses, number of employees, hours of operation, number of acres, etc. Please provide the names, telephone numbers, and addresses of the property owner(s), applicant representatives, or potential developers.
      2. A Vicinity Map: A vicinity map showing where the property is located within the City of Thornton.
      3. A Proposed Site Development Plan: This graphic should be drawn to scale and include a north arrow, building footprints, parking and landscape areas, access points, streets, potential park and open space areas and Rights-of-Way. Also identify any existing buildings on the site, natural features of the property which we should be made aware of, and any easements affecting the property.

      Optional items which help provide more detailed feedback:

      1. Building elevations and building materials.
      2. Occupancy classification.
      3. Subdivision lot arrangements.

      Once your submittal is prepared, please send an email to developmentsubmittals@thorntonco.gov for your meeting to be added to the scheduling queue.

      When to make a submittal:

      Pre-application meetings are scheduled on a first-come, first-served basis. The City schedules up to two (2) pre-application meetings each week on Thursdays. The above documents must be submitted to the City by 5 p.m. on Monday in order to schedule a meeting for the following week. Once both pre-application meeting time slots are filled for the week, requests are scheduled for the next available date and time in the order in which they were submitted. Due to the high volume of pre-application meeting requests, at times we are scheduling out several weeks from the date of submittal. Please contact the City Development department for current scheduling status.

      At the meeting:

      • You are welcome to bring anyone you wish to the pre-application meeting to discuss site development issues.
      • City representatives in attendance usually include a planner, development engineer, fire protection engineer and landscape architect. Building Inspection or Economic Development staff may attend as appropriate.
      • City staff is committed to providing exceptional customer service and information to help you make decisions about your project.
      • If you have any questions, please contact the Planner of the Day.
      Prairie Dog Relocation Information

      Evidence of Good Faith Effort

      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:

      1. 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.
      2. 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.
      3. 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 insure 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
      • Prairie Dog Action
      • Prairie Preserves, LLC, 303-280-8860
      • Animal & Pest Control Specialist, Inc.
      • Roe Ecological Services, LLC, 970-532-1305
      • Enviro-Zone, 303-735-0406
      • Dog Gone, 970-565-9878