Building permits, zoning and land rules in Custer County, Oklahoma

No county building permit is required for ordinary construction in unincorporated Custer County¹. A single-family dwelling, duplex, barn, shed or attached carport in an unincorporated county area also does not require the Oklahoma State Fire Marshal permit that can apply to other projects⁵. Two county approvals remain important: an encroachment on or into a county right-of-way requires a permit and applicable fees, and a project in a special flood hazard area requires a development permit¹. Oklahoma's statewide minimum building codes apply to residential construction in the state, and in unincorporated areas the Construction Industries Board enforces the electrical, mechanical, plumbing and fuel-gas codes, so trade work can still carry state licensing and permit rules even without a county building permit⁶. Custer County has not confirmed whether it has adopted a building code, requires construction inspections or issues certificates of occupancy, so ask the County Clerk and the relevant commissioner before finalizing plans. Inside a city or town, municipal ordinances may produce a different answer¹.

Custer County directs ingress and egress permit questions to the County Clerk, reachable at 580.323.4420 or at PO Box 300, 675 W. B Street, Arapaho, OK 73620⁷. The county’s forms page provides an ingress and egress permit and a floodplain permit application⁷. For a project in a special flood hazard area, the County Commissioner’s Office at the Arapaho courthouse holds the development-permit information¹. Oklahoma DEQ, rather than the county, handles septic authorization and assigns an application to the local environmental specialist based on the property location³. A driveway connecting to a federal or state highway requires an approved Oklahoma Department of Transportation Driveway Agreement before work begins in the highway right-of-way⁸.

Unincorporated Custer County has no county zoning ordinance, and the county’s statement expressly leaves state statutes and city ordinances in place¹. As a result, county zoning does not set a minimum dwelling size, minimum lot size, setbacks, lot coverage or building height on land outside incorporated municipalities¹. The same county zoning baseline does not restrict tiny-home occupancy, accessory dwellings or manufactured-home occupancy in unincorporated areas, but septic, floodplain, health and state installation rules can still control a project¹. An occupied manufactured home is treated as a permanent installation under Oklahoma rules and must follow the applicable approved installation standard⁹. For newly platted residential development outside municipal limits, state plat rules can require agency approval for smaller lots even though Custer County has no zoning minimum¹⁰.

Oklahoma DEQ issues the septic approval for Custer County: before a new system is installed or an existing system is modified, an Authorization to Construct must be purchased and issued³. DEQ first reviews the on-site sewage report, then assigns the authorization to the local environmental specialist based on the property location, and the installation must be inspected and approved before operation unless a certified installer follows the state’s self-inspection route, in which case the installer's inspection report goes to DEQ within 15 days of completion^2,3. Since November 1, 2025, an installer who is not DEQ-certified may install only one on-site sewage system per calendar year, which matters if you plan to install your own². Only 18.8% of Custer County soils are rated without severe limitations for a conventional drain field, so do not assume a standard lateral field will fit a parcel before soil evaluation¹¹. Contact Environmental Complaints & Local Services at 405-702-6100 for the specialist covering the property³. A qualifying domestic groundwater well does not need a state water permit, while a non-domestic well needs OWRB authorization and approval before drilling^4,12.

County zoning does not restrict RV occupancy, temporary camping or tiny-home occupancy on land in unincorporated Custer County¹. That answer is limited to county zoning: septic, public-health, floodplain and other property-specific rules can still apply, and city ordinances govern land inside incorporated municipalities¹. A tiny home has no county zoning minimum dwelling size in unincorporated Custer County, but the county has not confirmed a building code, inspection requirement or certificate-of-occupancy process¹. Ask the County Clerk about those unresolved construction questions and contact DEQ before installing or changing any on-site sewage system^3,7. An occupied manufactured home must comply with Oklahoma’s permanent-installation requirements even though county zoning does not bar the use^1,9.

1. Confirm that the parcel is outside an incorporated municipality; city ordinances can apply inside city limits even though unincorporated Custer County has no zoning¹.

1. Ask the County Clerk whether the site touches a county right-of-way or special flood hazard area, because those conditions trigger separate county permits¹.

1. Arrange the DEQ on-site sewage report and obtain an Authorization to Construct before installing or modifying septic³.

1. If access connects to a federal or state highway, obtain the ODOT Driveway Agreement before right-of-way work begins⁸.

1. Confirm water: qualifying domestic groundwater use needs no state water permit, but non-domestic drilling requires prior OWRB authorization^4,12.

1. Ask the County Clerk about building-code, inspection and occupancy questions that Custer County has not confirmed.

Check legal access, flood status, septic feasibility and water before closing. County right-of-way encroachments require a permit, and projects in a special flood hazard area require a development permit¹. With only 18.8% of county soils rated without severe conventional-drain-field limitations, a soil evaluation can materially change the usable building area and system choice¹¹. Custer County averages 28.6 inches of annual precipitation and experiences severe drought in 38.7% of years, so verify actual well records and water reliability for the parcel¹¹. About 98.3% of county land is at a slope of 15% or less, but parcel-level drainage and flood conditions still matter¹¹. For budgeting, the effective property-tax rate is about 0.7%, and the median annual property-tax bill is $1,197¹¹.