Building permits in unincorporated Williamson County — one of Tennessee's wealthiest and fastest-growing counties south of Nashville — are issued by the Williamson County Building Codes Division. Applications are submitted through the IDT Plans Electronic Plan Review System.
This Williamson County building permit guide covers what requires a permit in unincorporated areas, how the Building Codes Division works, the IDT Plans portal, fees, state-administered electrical permits, and inspections.
Williamson County issues permits for unincorporated areas only. The City of Franklin, City of Brentwood, and other municipalities run their own permitting. Electrical permits for unincorporated Williamson County are issued through the State of Tennessee at core.tn.gov (effective June 2023).
What requires a building permit in Williamson County?
Under the International Codes as adopted by Williamson County, a permit is required before constructing, enlarging, altering, repairing, moving, demolishing, or changing the occupancy of most structures. Common triggers include:
Permit required
- New residential and commercial construction, additions
- Structural and load-bearing alterations
- Reroofing, windows, doors, and exterior changes
- Electrical, plumbing, mechanical, and gas work
- HVAC installations and changeouts
- Decks, pools, fences, accessory structures
- Change of occupancy or use
- Pre-manufactured home placement
Typically exempt
- Painting, flooring, cabinetry, and cosmetic work
- One-story detached accessory structure ≤ 200 sq ft
- Replacement of existing fixtures (like-for-like swaps)
- Minor repairs not affecting structural or safety systems
Exemptions are narrow and scope-specific. When unsure, confirm with the building department before starting — see the penalty note below.
Get the permit issued before starting work. Building without one exposes the owner to penalties and stop-work orders. Note that exemption from a building permit does not exempt a project from zoning requirements — confirm edge cases with the building department.
Who handles permitting in Williamson County?
Permitting, plan review, and inspections run through the Williamson County Building Codes Division.
| Detail | Information |
|---|---|
| Office | Building Codes Division — 1320 West Main Street, Franklin, TN 37064 |
| Phone | (615) 790-5718 |
| Apply | IDT Plans (Electronic Plan Review) |
| Covers | Unincorporated Williamson County only |
| Code cycle | Locally adopted I-Codes |
| Hours | Monday–Friday, 8:00 AM – 4:30 PM (call to confirm) |
Contact the Building Codes Division to apply. Submit your building permit application with construction plans and required documentation. Call (615) 790-5718 for current forms and requirements.
Williamson County building permit cost
Williamson County building permit fees are set by the county fee schedule and based on project type and valuation. Separate trade permit fees apply. Confirm current amounts with the Building Codes Division.
| Fee component | How it works |
|---|---|
| Building permit fee | Per county fee schedule (type & valuation) |
| Plan review fee | Included in or separate from permit fee |
| Trade permits (E / P / M / Gas) | Separate fee per trade |
| Certificate of Occupancy | Required before legal occupancy |
| Work-without-permit | Penalties + enforcement action |
Want a precise number for a specific Williamson County project? Send us the scope and valuation and we'll return a fee estimate alongside a filing timeline.
Williamson County trade permits
Electrical, plumbing, mechanical, and gas permits are filed separately. Each requires a Tennessee-licensed trade contractor.
Electrical permits
Required for service upgrades, panel work, solar PV, and most wiring — performed by a TN-licensed electrical contractor.
Plumbing permits
Required for new plumbing, repipes, water heaters, and gas piping — performed by a TN-licensed plumber.
Mechanical (HVAC) permits
Required for HVAC installations, changeouts, ductwork, and refrigeration — performed by a TN-licensed mechanical contractor.
Miscellaneous & specialty
Reroofs, decks, pools, fences, accessory structures, and demolition are permitted separately.
Verify your contractor's license. Tennessee requires a state contractor license issued by the Tennessee Board for Licensing Contractors (under the Department of Commerce & Insurance / TDCI) for projects valued at $25,000 or more. Separate trade licenses are required for electrical (CE), plumbing, and HVAC/mechanical work. Homeowners may pull their own permit for personal-use construction once every 24 months under TCA § 62-6-103 — but the project must still meet all code and inspection requirements. Verify licensure at tn.gov/commerce/regboards/contractors.
How to get a building permit in Williamson County
Confirm jurisdiction & zoning
Verify the parcel is in unincorporated Williamson County (not within a municipality). Confirm zoning compliance.
Prepare application & plans
Complete the building permit application with construction plans, site plan, and required documentation.
Submit to Building Codes Division
Deliver the application as directed — in person or through the county portal.
Plan review & corrections
Building Codes Division reviews against adopted codes. Address comments and resubmit as needed.
Pay fees & pull the permit
Pay calculated fees. Post the permit card on site.
Schedule inspections through CO
Request inspections through the department. Clear all checkpoints for your Certificate of Occupancy.
Inspections in Williamson County
Schedule inspections through the Building Codes Division. Typical checkpoints include footing/foundation, framing, rough-in MEP, insulation, and final. Post the permit and approved plans on site. A final inspection and CO are required before occupancy.
Address correction notices before requesting a re-inspection; a final inspection and Certificate of Occupancy are required before legal occupancy or use.
Official Williamson County permitting resources
- 🏛️ Williamson County Building Codes Division
- 🪪 TN Board for Licensing Contractors
- 📘 TN State Fire Marshal
- 🔥 TN Dept. of Commerce & Insurance
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Williamson County's permitting process rewards applicants who confirm jurisdiction, assemble complete packages, and submit correctly from the start. Alliance Permitting is a permit expediter for Williamson County — our permit expediting services pair AI-driven document review with experts who know the Building Codes Division process, so your Williamson County submissions move faster.
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Alliance Permitting is a permit documentation and submission company: we prepare your paperwork, file it correctly, and coordinate with the building department through issuance — including preparing private-provider documentation where that option is available. We are not a contractor and do not perform licensed plan review or inspections; that work stays with your team and the jurisdiction.
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More Tennessee permitting guides
This guide is provided by Alliance Permitting for general informational purposes and reflects publicly available information believed accurate as of June 2026. Permit requirements, fees, and processes change; always confirm current details with the Williamson County Building Codes Division before filing. This is not legal advice.