This is PermitBase’s published record for Thornton as of 2026-07-01. It has since been superseded — see the current record. A historical record reflects what PermitBase had verified at that time; it may not capture a real-world change the jurisdiction had made but PermitBase had not yet verified, and it includes any errors we later corrected. Snapshots are never edited retroactively.
Thornton building permits
VerifiedThornton, Colorado — as published 2026-07-01.
Verified 2026-06-30 · Source
Codes 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International Residential Code (IRC) — with Thornton amendments (Table R301.2 climatic/geographic design criteria repealed and reenacted with Thornton-specific values); effective July 1, 20252024 International Plumbing Code (IPC) — with Thornton amendments; effective July 1, 20252024 International Mechanical Code (IMC) — with Thornton amendments; effective July 1, 20252024 International Fuel Gas Code (IFGC) — with Thornton amendments; effective July 1, 20252024 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, 20252024 International Existing Building Code (IEBC) — with Thornton amendments; effective July 1, 20252024 International Swimming Pool and Spa Code (ISPSC) — adopted by reference; effective July 1, 20252023 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matches the statewide electrical code2021 editions of the above I-Codes and the 2017 NEC — the prior code cycle, superseded for new submittals as of July 1, 2025 but referenced for projects permitted under it (e.g., the city's 2023-dated Solar PV submittal-requirements handout still cites 2020 NEC/2021 IRC/2021 IBC/2021 IFC and should be read as superseded by the current 2024/2023 code cycle for design-code citations)
Permit types & fees
Residential Building Permit (New Construction)
VerifiedRequired for new single-family homes and other new residential construction in Thornton. Reviewed against the 2024 International Residential Code (IRC) with Thornton amendments (including the City's own Table R301.2 climatic/geographic design criteria), effective July 1, 2025, and issued by the City Development Building Inspection Division.
Verified 2026-06-30 · Source
Requirements
- Building permit required for new single-family dwellings, room additions, and attached/detached garages
- Applications submitted online via the CityView Portal (cityviewportal.thorntonco.gov)
- Plans must comply with the 2024 IRC with Thornton amendments and the 2024 IECC (including Colorado Model Electric Ready and Solar Ready Code provisions)
- Structural design must meet Thornton's amended Table R301.2 criteria: 30 psf ground snow load, 105 mph ultimate wind speed, Seismic Design Category B, 36-inch frost depth, Severe weathering exposure
- Homeowners may qualify for expedited one-business-day review for complete, standard-code submittals
- Valuation is the estimated cost to replace the building in kind (labor, materials, overhead, profit); new construction valuation may be calculated using ICC square-footage valuation tables
Required documents
- RequiredBuilding Permit Application (CityView Portal)Online application through the City of Thornton's CityView Portal
- RequiredSite PlanProperty lines, setbacks, existing/proposed structures, easements, drainage
- RequiredConstruction DrawingsFull plan set: foundation, framing, structural, mechanical, plumbing, electrical, bearing the seal/signature of a design professional where required
- OptionalPlumbing Data Worksheet2024 IPC water fixture unit (F.U.) calculation sheet, required when adding fixtures to an existing water service; also used for ADU and tenant-finish plumbing scope
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Building Permit Fee — valuation $1.00 to $500 | $30.00 | City of Thornton 2026 Building Permit Fee Schedule, effective January 1, 2026 (updated 11/25/2025) |
| Building Permit Fee — valuation $501 to $2,000 | $30.00 for the first $500 plus $3.15 for each additional $100 or fraction thereof | — |
| Building Permit Fee — valuation $2,001 to $25,000 | $75.75 for the first $2,000 plus $14.40 for each additional $1,000 or fraction thereof | — |
| Building Permit Fee — valuation $25,001 to $50,000 | $397.75 for the first $25,000 plus $10.40 for each additional $1,000 or fraction thereof | — |
| Building Permit Fee — valuation $50,001 to $100,000 | $650.25 for the first $50,000 plus $7.20 for each additional $1,000 or fraction thereof | — |
| Building Permit Fee — valuation $100,001 to $500,000 | $1,000.25 for the first $100,000 plus $5.75 for each additional $1,000 or fraction thereof | — |
| Building Permit Fee — valuation $500,001 to $1,000,000 | $3,240.25 for the first $500,000 plus $4.90 for each additional $1,000 or fraction thereof | — |
| Building Permit Fee — valuation $1,000,001 and up | $5,615.25 for the first $1,000,000 plus $3.75 for each additional $1,000 or fraction thereof | — |
| Plan Review Fee | 65% of the Building Permit Fee | Third Party Plan Review Fee = 65% of Building Permit Fee, or Third-Party Review Fee + 10%, whichever is greater |
| Mechanical, Electrical & Plumbing Permit Fee — New Single Family Dwelling | $100.00 | Flat combined MEP fee for new single-family residential buildings, per the 2026 Fee Schedule |
| Use Tax | 3.75% of 50% of valuation, or 100% of total material cost | — |
Residential Addition / Remodel Permit
VerifiedRequired for room additions, basement finishes, structural alterations, and remodels to existing homes in Thornton. Reviewed against the 2024 IRC with Thornton amendments; uses the same valuation-based fee table as new construction.
Verified 2026-06-30 · Source
Requirements
- Room additions, basement finishes, structural modifications, and attached/detached garages require a building permit
- Remodel/renovation/alteration project valuation is calculated as labor + material cost, or material cost x2, whichever method the applicant provides support for
- Plans must show scope, dimensions, structural connection to the existing structure, and compliance with the amended Table R301.2 design criteria where structural work is involved
- For Accessory Dwelling Units (ADUs) created via basement/garage/attic finish (Integrated ADU), contact Planning before building permit submittal (303-538-7295) — additional zoning requirements apply
- Applications submitted via the CityView Portal
Required documents
- RequiredBuilding Permit Application (CityView Portal)Online application; select the remodel/addition project scope
- RequiredSite PlanProperty lines, existing structures, proposed addition footprint and setbacks
- RequiredConstruction DrawingsPlans showing the addition/remodel scope, including structural calculations if structural work is involved
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Building Permit Fee — valuation-based (same table as new construction) | Varies by valuation — $30.00 minimum up to $5,615.25 + $3.75/$1,000 over $1,000,000 | City of Thornton 2026 Building Permit Fee Schedule; remodel/renovation/alteration valuation = labor + material cost, or material cost x2 |
| Plan Review Fee | 65% of the Building Permit Fee | — |
| Additional Plan Review (changes, additions, or revisions to plans) | $75.00 or actual hourly cost to the jurisdiction, whichever is greater | — |
| Mechanical, Electrical & Plumbing trade permit fees | $30.00 for the first $1,000 of trade valuation, plus $10.00 for each additional $1,000 or fraction thereof, per trade | Applies when a remodel/addition includes plumbing, mechanical, and/or electrical work — each trade charged separately based on that trade's valuation |
Electrical Permit
VerifiedRequired for electrical installations, alterations, service changes, and main panel upgrades in Thornton. Governed by the National Electrical Code edition currently adopted by the State of Colorado (2023 NEC), which Thornton automatically adopts in sync per City Code Sec. 10-162. The City of Thornton's Building Inspection Division — not a state agency — issues and inspects electrical permits inside city limits; electrical contractors must hold a current State of Colorado Electrical Contractor license and Master Electrician license as a prerequisite to the City's no-fee Electrical Class D Specialty contractor license.
Verified 2026-06-30 · Source
Requirements
- Electrical contractor must hold a current State of Colorado Electrical Contractor license (issued by DORA's State Electrical Board) AND a City of Thornton Electrical contractor license (Class D Specialty — no City fee, but state and master licenses are a prerequisite)
- City of Thornton Electrical Contractor Registration is valid for two (2) years (longer than the standard one-year cycle for other Thornton contractor license classes)
- Main service panel upgrades, rewiring, new circuits, and EV charger installations require a permit
- Homeowners doing electrical work on their own private residence are exempt from the City contractor-license requirement (per Thornton City Code Sec. 10-121), but the permit itself is still required
- Governed by the National Electrical Code edition currently adopted by the State of Colorado (2023 NEC as of this code cycle); Thornton's adoption occurs automatically and simultaneously with the State's adoption (City Code Sec. 10-162), so Thornton does not independently amend the NEC edition/timing
- Applications submitted via the CityView Portal
Required documents
- RequiredElectrical Permit Application (CityView Portal)Online application through the City of Thornton's CityView Portal
- OptionalSub-Contractor Permission FormRequired when an electrical contractor works as a sub-contractor under a general contractor; a new form is required for each project
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Electrical Permit Fee — trade valuation $0 to $1,000 | $30.00 | City of Thornton 2026 Building Permit Fee Schedule — 'Other Permit Fees including Mechanical, Electrical, Plumbing' table; also used as a standalone electrical-only permit fee |
| Electrical Permit Fee — trade valuation $1,001 and up | $30.00 for the first $1,000 plus $10.00 for each additional $1,000 or fraction thereof | — |
| Mechanical, Electrical & Plumbing Fee — New Single Family Dwelling (combined) | $100.00 | Flat fee when electrical is part of a new single-family building permit rather than a standalone trade permit |
| Electric Meter (Miscellaneous Fee) | $25.00 | — |
| Contractor License — Class D Specialty (Electrical) | No fee | City of Thornton Contractor License Table (2024/2026): 'Electrical (state and master licenses required) — NO FEE' |
Plumbing Permit
VerifiedRequired for plumbing installations, alterations, and repairs in Thornton. Governed by the 2024 International Plumbing Code (IPC) with Thornton amendments, effective July 1, 2025. The City of Thornton's Building Inspection Division issues and inspects plumbing permits inside city limits; plumbing contractors must hold a current State of Colorado Plumbing Contractor license and Master Plumber license as a prerequisite to the City's Plumbing Class D Specialty contractor license.
Verified 2026-06-30 · Source
Requirements
- Plumbing contractor must hold a current State of Colorado Plumbing Contractor license (issued by DORA's State Plumbing Board) AND a City of Thornton Plumbing contractor license (Class D Specialty, $75.00)
- Water heater installation/replacement, re-piping, new fixtures, and graywater systems require a permit
- Homeowners doing plumbing work on their own private residence are exempt from the City contractor-license requirement, but the permit itself is still required
- Governed by the 2024 International Plumbing Code (IPC) with Thornton amendments, effective July 1, 2025
- Plumbing Data Worksheet (2024 IPC water fixture unit calculation) required when adding fixtures to an existing water service
- Applications submitted via the CityView Portal
Required documents
- RequiredPlumbing Permit Application (CityView Portal)Online application through the City of Thornton's CityView Portal
- OptionalPlumbing Data Worksheet2024 IPC water fixture unit (F.U.) calculation, required for fixture additions to an existing water service
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Plumbing Permit Fee — trade valuation $0 to $1,000 | $30.00 | City of Thornton 2026 Building Permit Fee Schedule — 'Other Permit Fees including Mechanical, Electrical, Plumbing' table |
| Plumbing Permit Fee — trade valuation $1,001 and up | $30.00 for the first $1,000 plus $10.00 for each additional $1,000 or fraction thereof | — |
| Mechanical, Electrical & Plumbing Fee — New Single Family Dwelling (combined) | $100.00 | Flat fee when plumbing is part of a new single-family building permit rather than a standalone trade permit |
| Lawn Sprinkler / Backflow (new residential or commercial) | $15.00 | — |
| Sanitary Sewer — 1 unit | $11.00 | — |
| Sanitary Sewer — 2 or more units | $8.00/unit | — |
| Contractor License — Class D Specialty (Plumbing) | $75.00 | City of Thornton Contractor License Table: 'Plumbing (state and master licenses required)' — $75.00 Class D Specialty fee |
Mechanical / HVAC Permit
VerifiedRequired for furnace, air conditioning, boiler, and fuel-gas equipment installations in Thornton. Governed by the 2024 International Mechanical Code (IMC) and 2024 International Fuel Gas Code (IFGC), both with Thornton amendments, effective July 1, 2025.
Verified 2026-06-30 · Source
Requirements
- Furnace/AC installation or replacement, boiler installation or replacement, gas logs and gas lines, fireplaces (wood, pellet, gas), and whole-house fans require a permit
- Water softening system installation/replacement requires a permit
- Backup power generators / Energy Storage Systems require a permit
- Electric-to-gas or gas-to-electric conversions require a permit
- Mechanical contractor requires an ICC certification or reciprocal license (Class D Specialty — Mechanical, $75.00) unless the general contractor's license covers the scope
- Applications submitted via the CityView Portal
Required documents
- RequiredMechanical Permit Application (CityView Portal)Online application through the City of Thornton's CityView Portal
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Mechanical Permit Fee — trade valuation $0 to $1,000 | $30.00 | City of Thornton 2026 Building Permit Fee Schedule — 'Other Permit Fees including Mechanical, Electrical, Plumbing' table |
| Mechanical Permit Fee — trade valuation $1,001 and up | $30.00 for the first $1,000 plus $10.00 for each additional $1,000 or fraction thereof | — |
| Mechanical, Electrical & Plumbing Fee — New Single Family Dwelling (combined) | $100.00 | Flat fee when mechanical is part of a new single-family building permit rather than a standalone trade permit |
| Contractor License — Class D Specialty (Mechanical / Boiler / Gas Piping) | $75.00 | City of Thornton Contractor License Table; ICC or reciprocal license required for Mechanical |
Roofing Permit (Reroof)
VerifiedRequired for roof replacement in Thornton when more than one square (100 sq ft) of roof covering is replaced. Replacement of one square or less is treated as a repair and does not require a permit. Governed by Thornton's Roofing Standards handout and the 2024 IRC/IBC.
Verified 2026-06-30 · Source
Requirements
- A permit is required when more than one square (100 sq. ft.) of roof covering is replaced; one square or less is a repair, no permit required
- Each slope containing damaged shingles must be replaced in its entirety — partial replacement of asphalt roofing on a single slope is not allowed
- Ice and water shield is required only if specified in the shingle manufacturer's installation instructions (not required jurisdiction-wide)
- Drip edge flashing required at eaves and rakes, extending over the plywood sheathing at the fascia
- Multi-unit buildings (apartments, condos, duplexes, townhomes) sharing a single address apply on one application and receive one permit; individually addressed units apply on one application listing each address
- Applications submitted via the CityView Portal
Required documents
- RequiredRoofing Permit Application (CityView Portal)Online application through the City of Thornton's CityView Portal
- OptionalRoofing Standards handoutThornton's current roofing permit scope, underlayment, flashing, and inspection requirements (updated 9/12/2025)
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Roofing Permit Fee — treated as 'Other Permit Fee' (trade valuation $0 to $1,000) | $30.00 | City of Thornton 2026 Building Permit Fee Schedule lists Roofing under 'Other Permit Fees including Mechanical, Electrical, Plumbing, Roofing, Siding, and Fences' using the same $30 (first $1,000) + $10/$1,000 valuation-based formula |
| Roofing Permit Fee — trade valuation $1,001 and up | $30.00 for the first $1,000 plus $10.00 for each additional $1,000 or fraction thereof | — |
Solar PV Permit
VerifiedRequired for installation of rooftop or ground-mounted solar photovoltaic systems in Thornton. Reviewed by the City Development Building Inspection Division against the currently adopted IRC/IBC/IFC/NEC (2024/2023 cycle, effective July 1, 2025) and the Colorado Model Electric Ready and Solar Ready Code (HB22-1362). Fee valuation is calculated at $3.50/watt, capped at $500 residential / $1,000 commercial.
Verified 2026-07-01 · Source
Requirements
- Plans submitted electronically via the CityView Portal; a separate plan review is required for each property/address
- Commercial systems and the structural portion of residential plans must bear the stamp/signature of a Colorado-licensed professional engineer
- One-line diagram required showing module count/wattage, conductor sizes, conduit sizes, fuses/breaker ratings, inverter ratings, AC/DC disconnect ratings, main panel bus rating, batteries, and grounding means
- Structural engineering analysis required (both residential and commercial) verifying the existing roof structure is adequate for additional dead and wind-uplift loads, per Thornton's amended Table R301.2 wind/snow criteria
- Signed contract with total labor + material cost must be submitted and must match the permit application valuation; main panel upgrade valuation must be separated into its own MPU permit
- Panel upgrades performed in conjunction with a PV installation require a separate permit — if a panel replacement is discovered mid-inspection, the PV inspection halts until the panel-upgrade permit is issued
- Accessory solar collectors are permitted in all zoning districts provided they are not located in the front yard and are not used for commercial enterprise
Required documents
- RequiredSolar PV Permit Application (CityView Portal)Online application through the City of Thornton's CityView Portal
- RequiredPlan Review Submittal Requirements for Solar Photovoltaic SystemsThornton's solar-specific plan set, electrical, and structural submittal checklist (last updated May 22, 2023 — cites the prior 2020 NEC/2021 IRC/IBC/IFC design codes; current 2024/2023-cycle codes supersede those citations for code-edition purposes, but the submittal checklist content still applies)
- RequiredStructural Engineer LetterSeparate, individually uploaded letter from a Colorado-licensed engineer verifying roof adequacy for additional PV dead/wind-uplift loads
- RequiredManufacturer Cut SheetsUL/ETL/CSAus-listed cut sheets for modules, inverters, batteries, and mounting systems/feet
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Building Permit Fee — Solar PV (valuation-based, capped) | Valuation calculated at $3.50/watt; resulting fee capped at $500.00 (residential) or $1,000.00 (commercial) | City of Thornton 2026 Building Permit Fee Schedule — 'Miscellaneous Fees' section, Solar note |
| Plan Review Fee | 65% of the Building Permit Fee (subject to the same $500/$1,000 cap dynamics as the underlying permit fee) | — |
Accessory Dwelling Unit (ADU) Permit
VerifiedRequired for construction of a Detached, Attached, or Integrated ADU on a residential property in Thornton, per Thornton City Code Section 18-339. ADUs are allowed on most lots zoned RE, RL, RM, RH, AG, or SFD-L that permit a Dwelling, 1-Unit Detached, unless the primary dwelling already has two kitchens.
Verified 2026-06-30 · Source
Requirements
- Property must be zoned RE, RL, RM, RH, AG, or SFD-L with an existing or planned primary use of Dwelling, 1-Unit Detached
- Primary dwelling must have only one kitchen (properties with an ADU may have only one full kitchen in the principal dwelling)
- At least 3 parking spaces required on the property, with 1 space in a garage
- ADU size limited to no more than 50% of the primary dwelling size or 1,000 sq ft, whichever is GREATER (garage, porch, and similar areas excluded from the calculation)
- ADU requires a separate exterior access and its own address
- Detached ADUs must be set back 5 feet from side and rear property lines, with a maximum height of 16 feet (different standards apply in the RE zone)
- Detached ADUs over 500 sq ft and visible from the right-of-way require an approved Development Plan from City Development; under 500 sq ft or not visible from the right-of-way, no Development Plan required
- Attached ADUs (building additions) over 500 sq ft also require a Development Plan; attached ADUs must meet the primary use's zone-district setbacks/height and cannot have an interior entry to the primary dwelling
- Property owner's primary residence must be in either the primary dwelling or the ADU
- A deed restriction (template provided in the City's ADU Handbook) must be recorded with the Adams County Clerk and Recorder's Office prior to Building Permit issuance
- ADU utilizes the same water/sewer connections as the primary dwelling, but additional utility connection fees apply (contact Utility Billing, 303-538-7370)
Required documents
- RequiredBuilding Permit Application (CityView Portal)Submitted after Planning approval of the ADU
- OptionalAccessory Dwelling Unit HandbookCity of Thornton's ADU type definitions, requirements, deed restriction template, and Plumbing Data Worksheet
- OptionalDevelopment PlanRequired for Detached ADUs over 500 sq ft visible from the right-of-way, and Attached ADUs (additions) over 500 sq ft; approved by City Development before the Building Permit
- RequiredDeed RestrictionRecorded with the Adams County Clerk and Recorder's Office, with the property's legal description attached, prior to Building Permit issuance
- OptionalPlumbing Data Worksheet2024 IPC water fixture unit calculation, submitted with the Building Permit application if adding fixtures to the existing water service
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Building Permit Fee — valuation-based (same table as new construction) | Varies by valuation — see Residential Building Permit fee tiers (2026 Fee Schedule) | Thornton's 2026 Fee Schedule does not publish an ADU-specific fee variance; ADUs use the same valuation-based Building Permit fee table as other residential construction |
| Plan Review Fee | 65% of the Building Permit Fee | — |
| Utility Connection Fee | Not published as a fixed dollar figure in sources reviewed — contact Utility Billing (utilbilling@thorntonco.gov, 303-538-7370) for current ADU utility connection fee amount | ADU Handbook confirms additional utility connection fees apply beyond the shared water/sewer connection, but does not publish a specific dollar amount |
Demolition Permit
VerifiedRequired for demolition of structures in Thornton. Processed through the City Development Building Inspection Division at a flat published fee.
Verified 2026-06-30 · Source
Requirements
- Demolition permit required for removal of structures
- Utility disconnects (gas, electric, water, sewer) must be verified or arranged prior to demolition
- A demolition permit is required first if an existing structure is being removed to make way for a new deck, patio cover, or other new construction
- Applications submitted via the CityView Portal
Required documents
- RequiredDemolition Permit Application (CityView Portal)Online application through the City of Thornton's CityView Portal
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Demolition Permit (flat fee) | $50.00 | City of Thornton 2026 Building Permit Fee Schedule — 'Miscellaneous Fees' section |
Commercial Tenant Improvement Permit
VerifiedRequired for tenant finish and remodel work in commercial spaces in Thornton. Reviewed by the City Development Building Inspection Division against the currently adopted commercial codes (2024 IBC/IMC/IPC/IFGC with Thornton amendments, effective July 1, 2025); Thornton publishes a target first-review timeline of 13 working days or less.
Verified 2026-06-30 · Source
Requirements
- Complete permit application online via the CityView Portal (registered account required)
- One set of construction drawings required, including a code analysis on the title page, floor plan, wall sections, electrical one-line diagram, mechanical plan, plumbing plan, special systems plan, and (if exterior changes) elevation plans, plus a site plan showing the project's location relative to the building and parking areas
- All plans must bear the original seal and signature of a design professional
- Special Systems plans include fire-rated assemblies, fire stopping, fire/smoke dampers, hood systems, and grease traps/interceptors
- Fire protection system plans must be submitted to and approved by the Fire Department prior to permit issuance
- A complete Com-Check report based on the currently adopted Energy Code, bearing the seal/signature of the mechanical engineer, is required
- A completed water meter form bearing the mechanical engineer's original seal and signature is required
- Code analysis must include occupancy group, construction type, number of stories, building height, actual/allowable floor area, occupant load, exit count/width, and required plumbing fixture calculations
- Permit is not automatically issued — application is reviewed for approval, then payment is made, then the permit is processed and issued
Required documents
- RequiredCommercial Tenant Finish Permit Application (CityView Portal)Online application; registered portal account required
- RequiredPlan Review Submittal Requirements — Commercial Tenant FinishThornton's checklist for construction drawing content, Com-Check, and water meter form (effective 9/14/2021)
- RequiredCom-Check ReportEnergy code compliance report based on the currently adopted Energy Code (2024 IECC), sealed by the mechanical engineer
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Building Permit Fee — valuation-based (same table as new construction) | Varies by valuation — $30.00 minimum up to $5,615.25 + $3.75/$1,000 over $1,000,000 | City of Thornton 2026 Building Permit Fee Schedule Table 1; commercial tenant finish valuation follows the same schedule as residential |
| Plan Review Fee | 65% of the Building Permit Fee | — |
| Mechanical, Electrical & Plumbing trade permit fees | $30.00 for the first $1,000 of trade valuation, plus $10.00 for each additional $1,000 or fraction thereof, per trade | Applies separately for each trade (mechanical, electrical, plumbing) included in the tenant finish scope |
Deck / Covered Patio Permit
VerifiedRequired for construction of decks, patio covers, awnings, and carports in Thornton. Attached decks of any height, decks serving the main exit door, decks with attached roofs 200 sq ft or larger, and all patio covers/awnings/carports require a Building Permit. Reviewed against the 2024 IRC with Thornton amendments, using the Colorado Chapter ICC prescriptive residential patio cover/carport building guide adapted for Thornton.
Verified 2026-06-30 · Source
Requirements
- Attached decks of any height above ground level require a permit
- Any deck that serves the main exit door requires a permit, regardless of height
- Any deck with an attached roof of 200 sq ft or larger requires a permit
- Patio covers, awnings, and carports require a permit regardless of size
- Detached decks less than 200 sq ft AND less than 30 inches above grade that do not serve the main exit door do NOT require a permit
- Patios consisting only of flatwork (no roof) do not require a building permit
- Decks greater than 480 sq ft in the front yard require a Minor Development Permit (MDP) in addition to the building permit
- Rear-yard decks between 30 inches and 8 feet in height may encroach into the required rear setback up to 10 feet from the rear property line (not into easements); decks over 8 feet must meet the full rear setback
- Structural design (rafter/beam sizing, footings) must comply with Thornton's amended Table R301.2 wind/snow criteria
- Zoning approval is required for all patio cover/carport projects in addition to the building permit
Required documents
- RequiredBuilding Permit Application (CityView Portal)Online application through the City of Thornton's CityView Portal
- OptionalSingle Family Residential Patio Covers and Carports Building GuideColorado Chapter ICC prescriptive building guide, adapted for City of Thornton submittals — site plan, framing details, and construction specifications
- RequiredSite Plan (2 copies)Scaled plot plans showing project dimensions and relationship to existing structures/property lines
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Building Permit Fee — valuation-based (same table as new construction) | Varies by valuation — $30.00 minimum | City of Thornton 2026 Building Permit Fee Schedule Table 1; Thornton does not publish a separate flat deck/patio-cover fee — decks, patio covers, and carports requiring a building permit use the standard valuation-based schedule |
| Plan Review Fee | 65% of the Building Permit Fee | — |
Sources & verification
Verified against official sources. Last reviewed 2026-06-30.
Fee schedules
Applications & forms
Checklists & handouts
Codes & ordinances
Department & other records
Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Thornton building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.