Bolthole Index

Stephens County, Oklahoma

Zoning, building permits and septic rules in Duncan, Oklahoma

Duncan, Oklahoma, in Stephens County, runs its own zoning under the Zoning Ordinance of the City of Duncan1 and adopts the International Residential Code for buildings inside city limits2. The city's Community Development Department reviews and issues building permits3. Septic permits come from the state, not the city: the Oklahoma Department of Environmental Quality issues the Authorization to Construct4.

At a glance

Zoning
Yes, city zoning ordinance inside Duncan limits1
Building code
International Residential Code adopted2
Building permits
Reviewed and issued by Duncan Community Development3
Septic
State DEQ Authorization to Construct4
Water well inside city
City well permit required5

Who to call

Building permits

City of Duncan Community Development Department

Building permits, new-construction inspections, planning and zoning questions inside Duncan city limits

580-252-0250

1600 Highway 81 Duncan, OK 73533

Septic permits

Oklahoma Department of Environmental Quality, On-Site Sewage Program

Authorization to Construct review and issuance for on-site sewage systems

405-702-0100

707 N Robinson, Oklahoma City, OK, 73102

Contact details are copied from each office’s official page and were checked against it on October 24, 2026.

Off-grid gear

Going off-grid in Duncan means bringing your own water and power. The kit we’d start with:

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Does Duncan, Oklahoma have zoning?

Yes. Duncan, Oklahoma has a zoning ordinance of its own, the Zoning Ordinance of the City of Duncan, and it applies to land inside city limits1. Zoning is set by district, so check the district of the exact lot. In the R-1 Single-Family Residential District the minimum front yard is 25 feet, and an interior-lot side yard is at least 5 feet for a one-story dwelling and at least 10 feet for a taller one6. In the A-1 General Agricultural District, buildings sit at least 25 feet back from the right-of-way line, and a one-story interior-lot dwelling needs a side yard of at least 8 feet7. R-1 buildings are limited to 35 feet and 2.5 stories except as the ordinance provides8.

We could not confirm Duncan's rules on minimum lot size, minimum dwelling size, accessory dwellings, tiny homes or temporary camping. Ask the Community Development Department3 before you plan an RV, tiny home or second dwelling.

Do you need a building permit in Duncan, and who issues it?

Duncan's Community Development Department reviews and issues building permits and inspects new construction inside city limits3. The city has adopted the International Residential Code, in its latest edition with amendments, for buildings and structures inside Duncan2. We did not find a provision spelling out the general residential permit requirement or an owner-builder exception in the city code, so call Community Development to confirm what your project needs. Inspection fees are set by the City Council by motion or resolution, and we could not find a current dollar schedule9. Oklahoma also adds a state fee of $4.00 per permit on permits issued by municipalities10.

How do septic permits work in Duncan?

Septic permits are a state matter. Before a new on-site sewage system is installed or an existing one modified, an Authorization to Construct must be purchased and issued by the Oklahoma Department of Environmental Quality411. New installations and modifications must also be inspected and approved by DEQ, or installed and self-inspected by a certified installer12. We could not find a Duncan city rule on septic systems inside city limits, so a lot connected to city sewer should be confirmed with Community Development3.

Can you drill a well or live in an RV or tiny home in Duncan?

Inside Duncan city limits, building or overhauling a well requires a city water well permit, which expires 90 days after issuance5. Plumbing and electrical inspections apply to wells drilled in city limits13. We could not confirm any Duncan rule on RV living, tiny homes or temporary camping on private land, so ask Community Development before you move anything onto a lot3.

Building a home in Duncan: the steps, in order

  1. Confirm the zoning district of the lot with Community Development3.
  2. Check setbacks and height for that district6.
  3. Get your building permit from the city, which adopts the International Residential Code2.
  4. If the lot is not on city sewer, obtain the DEQ Authorization to Construct before building a septic system4.
  5. Request building code inspections through Community Development3.

What stays with Stephens County, and what to check before you buy

Land outside Duncan city limits follows Stephens County and state rules, not the city's; see the Stephens County page for unincorporated land. Floodplain construction in Stephens County's FEMA-designated floodplains must be an approved permitted activity14, and we could not confirm how Duncan administers flood-hazard development inside the city. Stephens County's effective property tax rate is 0.7%15, with a median bill of $961 a year16.

Watch-outs

  • Inside Duncan city limits the city's zoning and building rules apply; the county's rules for unincorporated land do not1.
  • We could not confirm Duncan's general residential permit requirement, owner-builder exception, minimum lot size, accessory dwelling or short-term rental rules, so call Community Development3 before you buy.
  • Septic Authorization to Construct comes from DEQ, not the city4.

Sources

  1. codelibrary.amlegal.com (Duncan), quoted and re-checked
  2. §5-201 Building Code Adopted (Duncan), quoted and re-checked
  3. City of Duncan Community Development Department (duncanok.gov)
  4. On-Site Sewage Treatment, quoted and re-checked
  5. §5-1803 Permits and Inspection (Duncan), quoted and re-checked
  6. codelibrary.amlegal.com (Duncan), quoted and re-checked
  7. §12-323 Area Regulations (Duncan), quoted and re-checked
  8. §12-224 Height Regulations (Duncan), quoted and re-checked
  9. §5-203 Fee for Inspection (Duncan), quoted and re-checked
  10. oklahoma.gov, quoted and re-checked
  11. Oklahoma Department of Environmental Quality, On-Site Sewage Program (oklahoma.gov)
  12. On-Site Sewage Treatment, quoted and re-checked
  13. §5-1803 Permits and Inspection (Duncan), quoted and re-checked
  14. Floodplains Information | Stephens County Emergency Management, quoted and re-checked
  15. Effective property tax rate: Bolthole Index county data
  16. Median property tax bill: Bolthole Index county data

Written October 24, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.

Answers from the rulebook for Duncan

Duncan’s own rules

  • Building code adoptedAdopted (with conditions)

    Buildings and structures inside Duncan city limits.

    • Code copies are on file in the City Clerk's office.
    • The adopted codes include later editions and amendments described in §5-201.
    “The International Residential Code (IRC), the latest edition thereof, and any amendments thereto, as recommended by the International Code Council, is hereby adopted”
  • InspectionsRequired

    Well work inside Duncan city limits; this is limited to well-related plumbing/electrical inspections, not a general building-inspection finding.

    • Applicable inspections are required on wells drilled within city corporate limits.
    • The listed inspections are plumbing final, electrical underground, and electrical final.
    “the following inspections shall be required”
  • Local zoningPresent (with conditions)

    Land inside Duncan city limits.

    • The ordinance is titled the Zoning Ordinance of the City of Duncan.
    “shall be known as the Zoning Ordinance of the City of Duncan and may be cited as such.”
  • Well permitRequired

    Construction or overhaul of a well inside Duncan city limits.

    • Routine maintenance of preexisting wells is excluded when determined by the plumbing inspector or designee.
    • The well driller must notify the plumbing inspector or designee for that determination.
    • A permit expires 90 days after issuance; a new permit is required before resuming work after expiration.

    permit duration: 90 days (A new permit is required before work resumes after expiration.)

    “without first securing a water well permit.”
  • Permit feesVariable (with conditions)

    Duncan building inspections.

    • The amount is set by Council motion or resolution; no current dollar schedule was located in the opened code material.
    “All inspection fees shall be in such amounts as may be set by the Council by motion or resolution.”
  • Permit processPartial

    Water-well permit applications inside Duncan city limits.

    • This finding is limited to water wells, not the general residential building-permit process.
    • Incomplete applications are rejected or denied.
    • The permit process requires an approved application form and the information specified in §5-1803(E).
    “Incomplete applications shall be rejected or denied.”

Rules another office applies inside Duncan

Duncan does not set these itself; the county, a health district or the state does, and they apply to every address inside its limits.

  • SetbacksSpecified

    A-1 General Agricultural District inside Duncan city limits.

    • Roadside stands selling farm products grown on the premises are excepted from the stated rule.
    • Side-yard requirements are subject to §12-362.

    state, federal, county highway, or section-line-road front setback from right-of-way: >= 25 feet (Alternatively 75 feet from easement centerline, whichever is greater.) · other public-road or street front setback from right-of-way: >= 25 feet (Alternatively 55 feet from easement centerline, whichever is greater.) · one-story interior-lot dwelling side yard: >= 8 feet (Subject to §12-362.) · more-than-one-story interior-lot dwelling side yard: >= 12 feet (Subject to §12-362.)

    “all buildings shall set back a minimum of 25 feet from the right-of-way line”
    One more reviewed finding on this topic
    • Specified — R-1 Single-Family Residential District inside Duncan city limits.
      “The minimum depth of the front yard shall be 25 feet.”
  • Building heightSpecified

    R-1 Single-Family Residential District inside Duncan city limits.

    • The §12-362 exception applies.

    maximum building height: <= 35 feet (Except as provided in §12-362.) · maximum building stories: <= 2.5 stories (Except as provided in §12-362.)

    “No building shall exceed two and one-half stories or 35 feet in height except as provided in § 12-362.”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission; ask Duncan or Stephens County directly.

  • Building permit — New residential construction inside Duncan city limits.
  • Owner-builder exemption — Owner-built residential construction inside Duncan city limits.
  • Certificate of occupancy — Residential occupancy inside Duncan city limits.
  • Minimum dwelling size — Duncan residential and agricultural zoning districts.
  • Minimum lot size — Duncan residential and agricultural zoning districts.
12 more unanswered
  • Lot coverage
  • Camping on your land
  • Tiny homes
  • Accessory dwellings
  • Who permits septic
  • Septic permit
  • Septic inspection
  • Off-grid sanitation
  • Mandatory utility hookup
  • Driveway access
  • Building in a floodplain
  • Short-term rentals

Each answer was extracted from an official source and independently re-checked against that source by a second reviewer. That is an evidence check, not legal advice. Rules change; confirm with the authority before you buy or build.

Unanswered questions are usually a sign that Duncan publishes no rule on the point, not that none exists. Stephens County’s page lists the county offices to call.

← All of Stephens County: county rules, score and offices