Building permits, zoning and septic rules in Mercer County, Kentucky

Yes. Mercer County requires a building permit for virtually every structure placed on property in Mercer County or Harrodsburg, including homes, manufactured homes, additions, decks, garages, pools and accessory structures larger than 200 square feet¹. Kentucky has adopted statewide building and residential codes based on the 2015 International Building Code and International Residential Code with Kentucky amendments^10,11. Mercer County's local ordinance adds permits, inspections and occupancy approval for covered single-family work^1,12. The residential building-permit fee is $0.20 per square foot, subject to a $75 minimum². Concrete patios, driveways and fences under 6 feet are listed exemptions¹. Agricultural structures are exempt only when used for agriculture in an agricultural zoning district on a tract larger than 10 acres; the principal dwelling remains subject to permitting¹. A homeowner may personally perform permitted plumbing in a home the homeowner occupies or is building for personal residential use, provided the homeowner applies before work begins, files the required affidavit, follows the plumbing rules and has not received another new-home homeowner permit within the previous five years⁶. That rule does not waive the plumbing permit or establish that an owner may act as the general building contractor⁶.

The Mercer County Building Inspector is at 109 Short St., Harrodsburg, KY 40330 and can be reached at (859) 734-3375 or buildinginspector@mercerky.com¹. Office hours are 8 a.m. to 12 p.m. and 1 p.m. to 4:30 p.m.; permits and plan reviews are normally handled in the morning, while field inspections occur in the afternoon¹. Applicants provide ownership information, plans, a site plan and other listed project documents¹. Start with Planning & Zoning because staff verify use, setbacks and placement before the Building Inspector reviews construction plans and floodplain issues¹. Covered construction proceeds through footer, foundation, framing, insulation and final building inspections¹. Final plumbing, electrical or septic approvals must be complete before the final inspection is scheduled, after which the Building Inspector issues the Certificate of Occupancy¹.

Yes. Mercer County and Harrodsburg participate in joint planning and zoning, but Burgin does not participate and has no zoning ordinance or zoning map for property inside its city limits³. The commission is at 109 Short St., Harrodsburg, KY 40330 and can be reached at (859) 734-6066⁷. Mercer County zoning staff verify the proposed use, setbacks and placement before a permit goes to the Building Inspector¹. A preliminary zoning inspection checks setback compliance, and a final zoning inspection verifies use and size; neither inspection requires an appointment¹. If a proposed location may encroach on a setback, the applicant may request an on-site inspection by the enforcement officer¹. The county publishes district maps, but calls them general references and directs owners to commission staff for an official zoning determination³. We could not confirm the numeric setback schedule, minimum lot size, minimum dwelling size, lot coverage or height limits; ask the commission for the district rules on the parcel^1,7.

The Mercer County Health Department handles local onsite sewage evaluations, permits and inspections^1,5. The environmental and administrative line is (859) 734-2229, and the office is at 900 N. College St., Harrodsburg, KY 40330¹³. A site evaluation comes before the permit, and the permit must be obtained before construction of any part of a new or altered system⁵. A certified installer must follow the evaluation unless the homeowner obtains a homeowner permit from the local health department⁵. Every installed, constructed, altered or repaired system requires inspection by a certified inspector⁵. Only about 3.7% of Mercer County soils are rated without severe limitations for a conventional drain field, so make the evaluation an early purchase contingency¹⁴.

We could not confirm a temporary or permanent RV, park-model or tiny-home occupancy rule for unincorporated Mercer County; ask the Greater Harrodsburg/Mercer County Planning & Zoning Commission about the parcel before buying⁷. Within Harrodsburg city limits, a travel trailer or recreational vehicle may not be used for permanent habitation, while temporary habitation requires a conditional-use permit from the Board of Adjustments & Appeals¹⁵. That Harrodsburg rule does not answer the question for unincorporated land. A statewide rule allowing temporary sleep in a lawfully parked vehicle on a public road, street or parking lot for less than 12 hours likewise does not authorize long-term RV living on private property¹⁶. For a tiny home, ask Planning & Zoning to confirm the allowed use, setbacks, dwelling-size standards and whether the design will be treated as a site-built, manufactured or recreational unit⁷.

1. Ask the Greater Harrodsburg/Mercer County Planning & Zoning Commission to verify the parcel's district, allowed use, setbacks and placement; request an on-site inspection if the proposed location may encroach on a setback^1,3.

1. For land outside Harrodsburg, obtain the Mercer County Health Department septic evaluation; inside Harrodsburg, provide copies of paid water and sewer tap fees before final inspection¹.

1. Gather the ownership information, plans, site materials and other documents listed for the application¹.

1. Resolve driveway access. A new or additional farm or single-family driveway involving a state highway right-of-way requires written application to the Department of Highways District Engineer¹⁷.

1. Submit the residential application and fee to the Mercer County Building Inspector².

1. Obtain the state floodplain permit before construction in a floodplain and before the county issues its building permit¹.

1. Complete the preliminary and final zoning inspections, the required construction inspections, and all final trade or septic approvals before obtaining the Certificate of Occupancy¹.

Check septic feasibility before treating a building site as settled: only 3.7% of Mercer County soils are rated without severe limitations for a conventional drain field¹⁴. Ask Planning & Zoning for an official district determination because the published maps are general references³. Check flood status because construction, demolition or renovation in a floodplain requires a state permit before work starts¹. Confirm who controls the road before planning an entrance; a state-highway approach goes through the Department of Highways District Engineer¹⁷. Confirm whether the property is served by Harrodsburg water and sewer or needs a Health Department septic evaluation¹. A private well needs a Kentucky-certified driller but no separate owner application or fee⁹. Mercer County's effective property-tax rate is about 0.8%, the median annual tax bill is about $1,553, and typical home insurance is about $1,410 per year¹⁴.