Single-Level Homes & Barndominiums in Cass County, Missouri

Building a Home on Rural Land in Cass County: The Rules

Last verified October 2026 from Cass County's official documents. Rules apply to unincorporated land outside city limits. Always confirm with the county before you build.

Cass County has an adopted building code (the 2006 International Codes), county zoning, and a county septic permit. A building permit is required before any work starts.

• Building permit: “Work shall not be started until a permit has been issued!” (permit packet p.1)
• Building code: “All plans will be reviewed under the 2006 International Codes as adopted by Cass County.” (permit packet p.1)
• Fees: “Application fee in the amount of $350.00 ... ($300.00 Septic Permit, $50.00 Building Permit Application)” and “For Habitable Space $1.47 per sq. ft.” The county says “The total permit fees from the above table shall be reduced by 25 percent for Earth Contact or slab on grade buildings used for dwellings.” (permit packet p.1, p.5)
• Engineer's seal: Plans need an “original seal from a Missouri Registered Engineer” for “Vaulted roof / ceiling structures” and “Framed walls with studs over ten feet in length.” (permit packet p.3)
• Frost footing depth: “36 inch depth for frost protection” (permit packet p.3). That matches the 36 in. below grade every DreamStart plan uses.
• Inspections: Inspections are required at stages of construction, and “Request for final inspection will not be accepted without a final approval of the septic system” (inspections handout, p.3)
• Zoning: “The purpose of this Order is to promote the comfort, health, safety, prosperity, and general welfare of the citizens residing in the unincorporated areas of Cass County by dividing such into zones and districts” (Zoning Regulations §400.030)
• Minimum lot size: Agricultural (A): “Minimum Lot Area. Twenty (20) acres or more.” R-R: “Minimum Lot Area. Three (3) acres.” R-S: “Minimum Lot Area. One (1) acre.” (Zoning Regulations §§400.270–400.290)
• Minimum home size: “a minimum floor area of one thousand (1,000) square feet, excluding basements, open and screened porches, and garages, is required.” (Zoning Regulations §400.030)
• Homes per parcel: “except in Mixed Use and Industrial Zoning Districts, no legal lot of record shall contain more than one (1) principal structure.” In the Agricultural district: “Residential uses are permitted within this district with a maximum of two (2) single-family residences permitted on an agricultural tract of land of not less than twenty (20) acres.” (Zoning Regulations §§400.030, 400.270)
• Septic: “For any property in the unincorporated areas of Cass County a permit is required before construction, modification or repair of the on-site sewage disposal system. The fee for the permit shall be three hundred dollars ($300.00).” (wastewater rules p.3)
• Soil test: “A certified soil morphology evaluation, site review, construction plans and application completed by the owner or installer shall be submitted along with appropriate fee at the time of permit application.” (wastewater rules p.3)
• Lot size for a septic field: “Any parcel of land proposed to be served by a private sewer system composed of underground lateral distribution piping shall be a minimum of three (3) acres in size” (Zoning Regulations §400.030)

Who to call: Cass County Building Codes, Environmental Health and Zoning Department, 30508 S. West Outer Road, Harrisonville, MO 64701 · (816) 380-8134

Official source: Cass County building permit packet for new single-family dwellings (updated September 26, 2025) · Cass County Code, Chapter 400 Zoning Regulations · Cass County Wastewater Treatment Systems rules (revised February 4, 2026)

Note: Cass County's permit packet also asks for documentation of the connection to a public water system. Lagoons are not permitted on lots under 3 acres.