Ten counties.
Ten rulebooks.

The short version.

Unincorporated areas only. A city inside the county has its own rules. “Not stated” means we did not find it on the county’s official pages; call the office. Older code editions are as the county’s own pages state them; a newer edition may have been adopted since.

Cass County, MO

Who issues permits. Cass County Building Codes, Environmental Health and Zoning Department (Harrisonville) issues permits; applications must be made in person and work may not start before a permit is issued. Source

Residential code. County publications say Cass County adopted the 2006 International Residential Code; plans are reviewed under the 2006 International Codes. Source

Septic and well. A private sewage disposal permit (or exemption permit) is required when plumbing fixtures are installed; handled by the same county department. Subdivision regulations base lots on private septic on a 3-acre minimum. Well permitting is not published on the county pages we reviewed. Source

Minimum lot and zoning. 'A' Agricultural District: minimum lot area 20 acres, 400-ft minimum lot width, setbacks 50 ft front, 25 ft side, 50 ft rear; up to two single-family residences on a 20+ acre ag tract. Source

Shop, accessory and agricultural buildings. Residential accessory buildings: an accessory structure 'shall not be used as a dwelling'; accessory occupancy is not issued until the primary residence is complete; sidewalls max 16 ft (over 14 ft needs engineered plans). In the A district, farm structures have no height restriction. Source

Floodplain and entrances. Site plans must show designated floodplains and permits may be denied for noncompliance with the flood zone ordinance; the county code includes Chapter 415 Floodplain Management Order. Driveway/entrance permit is not published on the county pages we reviewed. Source

Contact. Cass County Building Codes, Environmental Health and Zoning Department, 30508 S. West Outer Road, Harrisonville, MO 64701; (816) 380-8134. Source

Clay County, MO

Who issues permits. Clay County Planning and Zoning Department requires permits and inspections for almost all construction, in unincorporated areas only; permits are submitted online. Source

Residential code. 2012 International Residential Code (with 2012 IBC/IPC/IMC/IFC and 2011 NEC), adopted by Ordinance 2012-ORD-24, effective January 1, 2013. Source

Septic and well. Septic permits for new construction come from the Environmental division of the Clay County Public Health Center (Health Department), which also inspects the system. Wells is not published on the county pages we reviewed. Source

Minimum lot and zoning. AG Agricultural District: minimum lot 20 acres, 300-ft width at building line, setbacks 50/25/50 ft; R-1 Residential Rural 10 acres; R-5 5 acres. Minimum living area 1,000 sq ft (1-story). Source

Shop, accessory and agricultural buildings. Using accessory buildings as principal dwellings is prohibited except during construction of a principal dwelling (one year, with permit and health approval). Detached accessory structures may not exceed the house footprint, except farm buildings on 5+ acres. Farm structures have no height limit. Source

Floodplain and entrances. Floodplain Administrator handles floodplain questions; Clay County Highway Department issues driveway permits (MoDOT for state highways), with inspection before issuance. Source

Contact. Clay County Planning and Zoning Department, 816-407-3380, pandz@claycountymo.gov. Source

Platte County, MO

Who issues permits. Platte County Planning and Zoning (building inspections division) issues single-family dwelling permits for unincorporated areas. Source

Residential code. 2018 International Residential Code as amended (with 2018 IBC, IPC, IMC, IFGC, IECC and 2017 NEC). Source

Septic and well. Septic tanks require a permit from the Platte County Health Department. Wells is not published on the county pages we reviewed. Source

Minimum lot and zoning. 'AG' Agricultural District: lot area of at least 40 acres for each dwelling; 400-ft lot width; 100-ft front and rear yards, 30-ft side yards; 35-ft height limit. Source

Shop, accessory and agricultural buildings. AG permits a primary single-family residence, accessory uses and an accessory dwelling (per Sec. 400.335); non-dwelling accessory buildings need 100-ft side setbacks; buildings may cover no more than 25% of the lot. Source

Floodplain and entrances. A Platte County Flood Development Permit is required for new construction, fill, grading or excavation in floodplain; a dwelling permit also requires an entrance permit from the road district or MoDOT. Source

Contact. Platte County Planning and Zoning (planning, zoning enforcement, engineering, stormwater, building inspections). Source

Jackson County, MO (unincorporated)

Who issues permits. Jackson County (Public Works development division) issues building permits for unincorporated areas; applications go to the Planning and Environmental Health Office. Source

Residential code. 2018 International Residential Code (with 2018 IBC, IMC, IECC, IFC, IEBC) per the 2025 unincorporated permit packet. Source

Septic and well. On-site wastewater permits (new system, existing system/new house, repair) are handled by the county's On-Site Wastewater program; UDC requires at least 3 acres for a new lot on an on-site septic system. Wells is not published on the county pages we reviewed. Source

Minimum lot and zoning. AG District: minimum lot 10 acres, 250-ft width, setbacks 50 ft front/rear, 30 ft side, 15% max impervious cover; RR Residential Ranchette is a 5-acre district. Source

Shop, accessory and agricultural buildings. County code defines an agricultural structure as not a place of human habitation; pole barns need permits, and designs with finished living quarters/office are charged at residential rate and capped at 1,000 sq ft. In residential zones, buildings over 600 sq ft need the primary use in place first. Source

Floodplain and entrances. Site plans must show FEMA flood hazard areas and design flood elevations; driveways need a county driveway permit, and a MoDOT permit if on a state road. Source

Contact. Jackson County Planning and Environmental Health Office (Public Works); On-Site Wastewater Specialist 816-881-4515. Source

Lafayette County, MO

Who issues permits. Lafayette County Planning & Economic Development issues building, septic and floodplain permits in unincorporated areas, by appointment only. Source

Septic and well. The county planning office regulates onsite wastewater systems on less than 20 acres under the Land Development Code, following Missouri DHSS standards; registered installer and perc test or soil morphology required. Wells is not published on the county pages we reviewed. Source

Shop, accessory and agricultural buildings. Accessory building permits are offered ($300) and a Temporary Accessory Dwelling permit exists; building permits are required for 'development' regardless of property size. Source

Floodplain and entrances. Floodplain development permit needed for new homes, accessory structures (barns, sheds), grading/fill and driveways or culverts in floodplain; county participates in NFIP. Source

Contact. Lafayette County Planning & Economic Development, 1001 Main St., Lexington, MO; 660-259-4439; planning@lafayettecountymo.gov. Source

Clinton County, MO

Who issues permits. Clinton County Planning and Zoning issues all building permits county-wide in unincorporated areas; permits are required. Source

Septic and well. On-site wastewater install/repair needs a permit: soil evaluation by a state-licensed evaluator, licensed installer, Health Department review and inspections. Subdivision lots planned for septic tank and laterals may be as small as 5 acres. Wells is not published on the county pages we reviewed. Source

Minimum lot and zoning. Agriculture District A applies to parcels of 20+ contiguous acres; Agriculture District B to 10-19.99 acres, where each dwelling needs at least 10 acres and 950 sq ft minimum living area. Source

Shop, accessory and agricultural buildings. Combined 'Home Build w/ Attached Garage or Accessory Building' permit charges living space and non-living accessory space at separate rates; a temporary living permit is available only for AG-A or AG-B parcels. Source

Floodplain and entrances. County driveway permit required for county-maintained roads (fee doubles if work starts first); MoDOT permit for state highways. Floodplain permit is not published on the county pages we reviewed. Source

Contact. Clinton County Planning & Zoning, 207 N. Main St., Room 3, Plattsburg, MO 64477; 816-539-3722; Health Department (wastewater) 816-539-2144. Source

Johnson County, KS (unincorporated)

Who issues permits. Johnson County Building Codes (Planning and Codes) issues permits for unincorporated areas; addresses inside a city go to that city. Source

Residential code. 2018 International Codes (including 2018 IRC) with county amendments, effective July 1, 2020; 2024 codes under consideration for Jan. 1, 2027. Source

Septic and well. Private septic: contact the county Environmental department (913-715-6900); public sewer via Wastewater (913-715-8500). Wells is not published on the county pages we reviewed. Source

Minimum lot and zoning. RUR Rural District: nominal lot area of at least 10 acres per dwelling, 300-ft minimum width, setbacks 50 ft front, 25 ft side/rear; residences max 40 ft tall. Source

Shop, accessory and agricultural buildings. Agricultural buildings must be used solely for agricultural use to skip plan-review steps and need a notarized Accessory Building Use Form; residential accessory buildings 200+ sq ft need a permit. Source

Floodplain and entrances. Contact Planning and Zoning for floodplain information; Public Works (913-715-8300) for an entrance if first structure or a new entrance. Source

Contact. Johnson County Building Codes / Planning and Zoning, 913-715-2200. Source

Miami County, KS

Who issues permits. Miami County Code Services Department handles building permits, inspections, contractor licensing and onsite wastewater enforcement. Source

Residential code. County FAQ states it enforces the 2006 International One and Two Family Dwelling Code (with 2006 IBC/IPC/IMC/IFC, 2005 NEC). Source

Septic and well. Soil profile analysis must precede a building permit; no permit until an onsite wastewater design is approved and an installation permit issued by Code Services. Environmental Health covers septic and water wells. Source

Minimum lot and zoning. AG Agricultural District: standard subdivisions at 1 dwelling per 20 acres with 20-acre minimum lots; agricultural preservation subdivisions allow 2-acre lots; 220-ft minimum width. Source

Shop, accessory and agricultural buildings. Structures used solely for agriculture may be exempt from zoning and building inspections (except electrical, plumbing, HVAC) via notarized certification; residential-purpose parcels under 20 acres are not eligible, and a change of use requires code compliance. Source

Floodplain and entrances. New or existing entrances off county roads need a highway entrance permit ($50) before a building permit; Road and Bridge sets requirements. Source

Contact. Miami County Code Services, 201 S. Pearl, Suite 201, Paola, KS 66071; (913) 294-4145. Source

Leavenworth County, KS

Who issues permits. Leavenworth County Planning & Zoning Department issues building permits (new home, secondary dwelling, accessory, agriculture); do not build before approval. Source

Residential code. Permit application cites the International Residential/Building Code, 2012 edition, adopted by the County Commission Nov. 12, 2025; agricultural buildings excluded from that statement. Source

Septic and well. County Sanitary Code (administered by Planning & Zoning) governs onsite wastewater in unincorporated areas using KDHE Bulletin 4-2; 1-acre minimum per living unit; water wells allowed on tracts of 5+ acres, smaller tracts need public water. Source

Minimum lot and zoning. Rural district classifications: RR-2.5 (2.5 acres, 200-ft frontage), RR-5 (5 acres, 300-ft frontage), RR-40 (40 acres, 630-ft frontage). Source

Shop, accessory and agricultural buildings. County offers an Agricultural Exemption Application covering single-family dwellings and accessory buildings, requiring farm activity documentation; ADUs allowed only in rural residential districts per zoning regs. Source

Floodplain and entrances. Permit application asks whether the site is in a floodplain and staff determine whether an entrance permit or state permit (over 1 acre disturbed) is needed; new homes need a passing soil profile. Source

Contact. Leavenworth County Planning & Zoning Department, 300 Walnut St., Suite 212, Leavenworth, KS 66048; 913-684-0465; PZ@LeavenworthCounty.Gov. Source

Franklin County, KS

Who issues permits. Franklin County Planning & Building Department reviews plans and issues building permits for unincorporated areas. Source

Residential code. County page states it adopted the 2003 edition of the International Residential Code. Source

Septic and well. Wastewater system permits come from the Franklin County Environmental Health Department; 3-acre minimum lot per living unit for a conventional system permit (2017 Environmental Sanitation Code). Code also licenses water well inspectors. Source

Minimum lot and zoning. A-1 Agricultural District minimum lot area 40 acres (or aliquot quarter-section division); A-2 Transitional Agriculture 20 acres; R-E 5-19.99 acres; R-3A 3-4.99 acres. Source

Shop, accessory and agricultural buildings. No building permit for structures used exclusively for agriculture, but zoning setbacks apply and a notarized Affidavit of Agricultural Use is required; pole barns have their own permit checklist. Source

Floodplain and entrances. Public Works permission is required before establishing or reconstructing any entrance. Floodplain permit is not published on the county pages we reviewed. Source

Contact. Franklin County Planning & Building Department, 1428 S. Main St., Suite 5, Ottawa, KS 66067; 785-229-3570. Source

Questions to settle before a builder quotes.

• Is the parcel unincorporated, and which zoning district is it in?
• Does the lot meet the district’s minimum area and width for a dwelling?
• Has the county health office approved a septic system for this lot, and who drills the well?
• Will any part of the building be lived in before the house is finished?
• Which permits does the builder pull, and which are left to you?

Quick answers.

Sources are official county pages and adopted codes, checked Oct 11, 2026. This is not legal advice; confirm with the county before you buy land or sign a contract. Land and permit source desk · Kansas City builders