Sign Permit in Thornton, Colorado

Thornton requires a sign permit for: A sign permit is required for all permanent signs constructed and maintained on private property within the City of Thornton, per Development Code Chapter 18, Article 11; Sign contractor must be licensed with the City of Thornton; the permit application must indicate the value of the work and, if new electrical is being installed, provide the electrical contractor's information and a signed permission slip; Submittal package must include scaled drawings of the proposed sign(s) in PDF form, scaled building elevations showing the sign's placement (if attached to a building), and a scaled site plan showing dimensions from the property line to the sign and all major structures; Electronic Changeable Copy signs require a letter of compliance with Municipal Code Section 18-750; wall signs must comply with Sections 18-730 and 18-735, and monument signs with Sections 18-740 and 18-743; Signs not exceeding 4 sq ft per sign face (40 sq ft cumulative per zone lot), window signs, temporary decorations, signs not legible from the right-of-way, and certain flags/vehicular signs are exempt from the Sign Code permit requirement, per Development Code Section 18-712; Animated signs, roof signs, building wrap signs, searchlights, signs in/over public rights-of-way, signs within a visibility triangle, signs causing a traffic hazard or obscuring traffic control devices, and signs attached to landscaping/natural objects are prohibited, per Development Code Section 18-713; Temporary signs do not require a sign permit but are subject to Development Code Chapter 18, Article 11, Division 6; Sign permits are effective for 180 days from the date of issuance or from the date of the last inspection; extension requests may be emailed to buildings@thorntonco.gov. If your project isn't listed, confirm with City of Thornton — City Development, Building Inspection Division at 303-538-7250 before starting work.

In Thornton, the published Sign Permit Fee is: Per the City's general Building Permit Fee Table: $30.00 minimum ($1-$500 valuation), scaling up to $75.75 for the first $2,000 plus $14.40 per additional $1,000 (up to $25,000), and further tiers through $5,615.25 for the first $1,000,000 plus $3.75 per additional $1,000 above that. These are the jurisdiction's own published figures — see the fee schedule table and source citations on this page.

In most cases, within 5 business days of submittal, per the City's Sign Permit Checklist. Building Inspection then contacts the applicant with the application status and fees.

You'll need: Building Permit Application (Sign) — CityView Portal; Scaled Sign Drawings, Building Elevations, and Site Plan (PDF). See the required-documents checklist on this page for details on each.

Apply through City of Thornton — City Development, Building Inspection Division at 9500 Civic Center Drive, Thornton, CO 80229. Phone: 303-538-7250, email: buildings@thorntonco.gov. Office hours: Mon–Fri, 8:00 a.m.–5:00 p.m. (counter payments 8:00 a.m.–4:30 p.m.). Official information: https://www.thorntonco.gov/business-development/city-development/building-permits-inspections.

Thornton, Colorado has adopted: 2024 International Building Code (IBC) — with Thornton amendments; adopted by ordinance May 13, 2025, effective July 1, 2025 (replaced the 2021 IBC); 2024 International Residential Code (IRC) — with Thornton amendments (Table R301.2 climatic/geographic design criteria repealed and reenacted with Thornton-specific values); effective July 1, 2025; 2024 International Plumbing Code (IPC) — with Thornton amendments; effective July 1, 2025; 2024 International Mechanical Code (IMC) — with Thornton amendments; effective July 1, 2025; 2024 International Fuel Gas Code (IFGC) — with Thornton amendments; effective July 1, 2025; 2024 International Energy Conservation Code (IECC) — adopted in full (residential provisions); includes Colorado Model Electric Ready and Solar Ready Code per HB22-1362; effective July 1, 2025; 2024 International Existing Building Code (IEBC) — with Thornton amendments; effective July 1, 2025; 2024 International Swimming Pool and Spa Code (ISPSC) — adopted by reference; effective July 1, 2025; 2023 National Electrical Code (NEC) / NFPA 70 — Thornton adopts the NEC edition currently adopted by the State of Colorado automatically and simultaneously (Thornton City Code Sec. 10-162); matches the statewide electrical code; 2021 editions of the above I-Codes and the 2017 NEC — the prior code cycle, superseded for new submittals as of July 1, 2025 but referenced for projects permitted under it (e.g., the city's 2023-dated Solar PV submittal-requirements handout still cites 2020 NEC/2021 IRC/2021 IBC/2021 IFC and should be read as superseded by the current 2024/2023 code cycle for design-code citations). Local amendments apply — see the Thornton overview page for the full list.

Yes, for all permanent signs constructed and maintained on private property. Temporary signs are exempt from the sign permit requirement but are still regulated under Development Code Chapter 18, Article 11, Division 6. A limited list of small/inconspicuous signs (e.g., under 4 sq ft per face) is also exempt under Section 18-712.