Bolthole Index

St. Louis County, Missouri

Zoning, building permits and septic rules in Fenton, Missouri

The City of Fenton, Missouri, in St. Louis County, administers its own zoning code1 and adopts its own building codes, with its Community Development Department as the building-code office2. Residents apply for permits through the city's online permit portal3. Septic permits are a separate question: the state lists the St. Louis County health and plumbing departments as the local authorities, and we could not confirm how that works inside city limits4.

At a glance

Zoning
Fenton administers its own zoning code inside city limits1
Building permits
Issued by the City of Fenton Community Development Department; apply through the city permit portal32
Building code
2015 International Building Code, as amended by St. Louis County2
Minimum lot, R-1
1 acre with 100 feet of width5
Minimum lot, R-3
10,000 square feet with 60 feet of width6
Septic
St. Louis County health and plumbing departments are the state-listed authorities; confirm for your address4
Wells
State well installation permit required in Missouri7

Who to call

Building permits

City of Fenton Community Development Department

Permit applications for building, zoning, land disturbance, floodplain development and occupancy inside Fenton city limits

636-349-8110

625 New Smizer Mill Road, Fenton, MO 63026

Septic permits

St. Louis County Department of Public Health

Septic (onsite wastewater) permitting for St. Louis County; ask whether an address inside Fenton falls under it

(314) 615-0600

administration.doh@stlouisco.com

6121 N Hanley Rd, Berkeley, MO 63134

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 Fenton means bringing your own water and power. The kit we’d start with:

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Does Fenton, Missouri have zoning, and what does it mean for lot size and setbacks?

Yes. The City of Fenton administers its own Title IV Zoning Code inside city limits1, with residential districts R-1 through R-58. St. Louis County's zoning applies only to unincorporated land, so it does not govern a Fenton lot9.

The numbers depend on the district. In R-1, the large-lot residential district, permitted uses need a lot of at least 1 acre with 100 feet of width5, and setbacks are 50 feet front, 15 feet side and 50 feet rear10. In R-3, the main single-family district, permitted uses need at least 10,000 square feet with 60 feet of width6; the R-3 rear setback is 30 feet or 20% of lot depth, whichever is larger, capped at 40 feet11. Buildings in both districts are limited to 40 feet in height12.

We did not confirm Fenton's rules on RVs, tiny homes or accessory dwellings, so ask Community Development before you plan one3.

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

Fenton adopts its building codes through its own city code, and the code names the City of Fenton Community Development Department as the building-code office2. The city's permit page lists a residential new construction permit and a zoning application permit among its applications3. We could not confirm the exact threshold for when a permit is required, so call Community Development at 636-349-8110 before starting work3.

The county's building permit rule in Chapter 1115 covers unincorporated St. Louis County, not Fenton13. Missouri leaves building codes to local adoption14.

Which building codes apply in Fenton?

Fenton adopts the 2015 International Building Code and related 2015 codes by reference, as amended by St. Louis County ordinances2. In the code, the city's Community Development director or designee acts as the code official2.

How do septic permits work inside Fenton?

Fenton's own code does not say who permits septic systems, and we could not confirm the answer for city addresses. Missouri requires a construction permit before installing or repairing most onsite wastewater systems15. The state lists the St. Louis County Plumbing Department and the St. Louis County Department of Public Health as the local authorities, and notes that incorporated areas may be handled differently4. Call the16 to find out who covers your address.

Missouri's statewide septic rules apply on any lot; the county's soil rating also suggests caution, since only about 5.4% of St. Louis County soils rate as not limited for a conventional drain field17. That is a county-wide figure, so expect a site evaluation if a lot is not on public sewer.

Building a home in Fenton: the steps, in order

  1. Confirm the zoning district of the lot and its minimum lot size and setbacks with Community Development13.
  2. Check the lot against flood maps; Fenton publishes a floodplain development application permit3.
  3. Apply for the residential new construction permit through the city's online portal3.
  4. Settle sewer or septic with the St. Louis County health department before you design the house4.
  5. If you plan a private well, Missouri requires a water well installation permit7.
  6. Ask Community Development about occupancy sign-off; the city lists a residential occupancy permit for new construction3.

What stays with St. Louis County, and what to check before you buy in Fenton

Septic and wells are not decided by the city's zoning code; see the county health department above4. For land outside Fenton's city limits, the county's rules apply instead; see the St. Louis County page. Typical home values in St. Louis County are about $293,45818, and the effective property tax rate is 1.2%19. Subdivision indentures may add private restrictions on top of city rules20.

Watch-outs

  • Fenton's chapter on permit requirements and site plan review was not confirmed, so ask Community Development which projects need a permit3.
  • The county's flood-plain, building-permit and zoning rules cover unincorporated land; inside Fenton the city's own code governs9.
  • Missouri has temporarily suspended application fees for onsite sewage system construction, modifications and repairs as of August 28, 202615.

Sources

  1. City of Fenton, MO Table of Contents - eCode360 (Fenton), quoted and re-checked
  2. Article I: County Code Adoptions - City of Fenton, MO (Chapter 500) (Fenton), quoted and re-checked
  3. City of Fenton Community Development Department (fentonmo.org)
  4. OWTS Construction Permit Process — St. Louis County authorities, quoted and re-checked
  5. Article III: Residential District Regulations - City of Fenton, MO (Chapter 415) (Fenton), quoted and re-checked
  6. Article III: Residential District Regulations - City of Fenton, MO (Chapter 415) (Fenton), quoted and re-checked
  7. Water Wells - PUB2945, quoted and re-checked
  8. Article III: Residential District Regulations - City of Fenton, MO (Chapter 415) (Fenton), quoted and re-checked
  9. Single-Family Dwelling Design Checklist, quoted and re-checked
  10. Article III: Residential District Regulations - City of Fenton, MO (Chapter 415) (Fenton), quoted and re-checked
  11. Article III: Residential District Regulations - City of Fenton, MO (Chapter 415) (Fenton), quoted and re-checked
  12. Article III: Residential District Regulations - City of Fenton, MO (Chapter 415) (Fenton), quoted and re-checked
  13. Chapter 1115 - Building Code, quoted and re-checked
  14. RSMo Section 64.170 (Missouri statewide rule), quoted and re-checked
  15. OWTS Construction Permit Process, quoted and re-checked
  16. St. Louis County Department of Public Health (stlouiscountymo.gov)
  17. Share of soils USDA rates "not limited" for a conventional septic drain field (SSURGO). A strict rating: the median county is about 6% and a tenth of counties are 0%, so a low figure means most lots need a site evaluation or an engineered system, not that septic is impossible. Cite it only with that caveat: Bolthole Index county data
  18. Typical home value (Zillow): Bolthole Index county data
  19. Effective property tax rate: Bolthole Index county data
  20. Single-Family Dwelling Design Checklist, quoted and re-checked

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 Fenton

Fenton’s own rules

  • Building code adoptedAdopted (with conditions)

    Construction inside Fenton city limits: the City of Fenton adopts the International Building Code 2015 and related codes by reference through its own code.

    • Adopted by reference, as amended by St. Louis County ordinances: IBC 2015, International Residential Code 2015, International Mechanical Code 2015, International Existing Building Code 2015, International Swimming Pool and Spa Code 2015, International Fuel Gas Code 2015, National Electrical Code 2014, Uniform Plumbing Code 2015, Property Maintenance Code 2015 (enforcement by the county problem property unit only), and the St. Louis County explosives and land disturbance codes.
    • The code says the county ordinance numbers 27,654 (IBC/IRC/IEBC/IPSC, adopted April 1, 2020, effective July 1, 2020) and related ordinances control the text; the city copy is kept on file with the city clerk.
    • Section 500.010 says the city adopts St. Louis County code provisions with the city substituted for county references; 'department of building inspection' means the City of Fenton community development department and 'code official' means the community development director or designee.
    • Violations carry a fine up to $500 and/or 90 days imprisonment per code.
    “1. building code. the "international building code, 2015 edition," as published by the international code council, as adopted, amended, and revised by st. louis county, missouri, pursuant to st. louis county ordinance no. 27,654 as adopted on april 1, 2020, effective july 1, 2020, is hereby incorporated by reference and adopted as the building code for the city, as if fully set out herein.”
  • Local zoningPresent (with conditions)

    Land inside Fenton city limits: the City of Fenton administers its own Title IV Zoning Code (chapters 400-445) on eCode360.

    • Zoning districts, use matrix, supplemental uses and subdivision rules are in chapters 410-445; only chapters 415 (Article III residential districts) and the table of contents were opened.
    • Chapter 420 land use matrix, chapter 425 accessory uses and chapter 430 supplemental uses were not opened.
    “title iv zoning code chapter 400 general provisions”
  • Zoning districtsPublished (with conditions)

    Zoning districts of the City of Fenton, inside city limits only.

    • Published districts include R-1 through R-5 (sections 415.030-415.065) per the eCode360 Article III index; Olde Towne (OT-3), commercial, office and industrial district chapters were not opened.
    • Each district's permitted uses are set by chapter 420 land use matrix, which was not opened.
    “the purpose of the "r-1" district is to allow for large-lot residential settings”
  • Minimum lot sizeSpecified

    Permitted uses in the R-1 residential district (large-lot residential) inside Fenton city limits

    • Uses allowed by special use permit must be on a lot of at least three (3) acres.
    • Flag lots are prohibited, except flag lots existing before November 20, 2017, which may not be further subdivided.
    • Page also lists ord. no. 4679 (2026-08-27) amending chapter 415; confirm the R-1 text against the current code.

    minimum lot area: >= 1 acre (or 43,560 square feet) · minimum lot width: >= 100 feet

    “permitted uses must be located on a lot containing at least one (1) acre or forty-three thousand five hundred sixty (43,560) square feet, with a minimum lot width of one hundred (100) feet.”
    One more reviewed finding on this topic
  • SetbacksSpecified

    Lots in the R-1 residential district inside Fenton city limits

    • Side setback may be reduced to not less than 10% of lot width, but not less than 5 feet, for a lot of record existing on the date of the code with a lot width of 75 feet or less.
    • Front setback 50 ft, side 15 ft, rear 50 ft are the minimum setbacks for each lot.

    front setback: >= 50 feet · side setback: >= 15 feet (reduced to 10% of lot width (min 5 ft) for lots of record 75 ft wide or less) · rear setback: >= 50 feet

    “each lot shall have a minimum fifty-foot front setback. b. side setback. each lot shall have a minimum fifteen-foot side setback; except, whenever a lot of record existing on the date of this code has a lot width of seventy-five (75) feet or less, the side setback may be reduced to a width of not less than ten percent (10%) of the lot width, but in no instance shall it be less than five (5) feet. c. rear setback. each lot shall have a minimum fifty-foot rear setback.”
    2 more reviewed findings on this topic
    • Specified — Lots in the R-2 residential district inside Fenton city limits (front and side only; rear setback not captured)
      “each lot shall have a minimum side setback of ten (10) feet; except, whenever a lot of record existing on the date of this code has a lot width of seventy-five (75) feet or less, the side setback may be reduced to a width of not less than”
    • Specified — Lots in the R-3 residential district (main single-family district) inside Fenton city limits (rear setback only; front and side not captured)
      “each lot shall have a rear setback of not less than thirty (30) feet or twenty percent (20%) of the lot depth, whichever amount is larger, but it need not exceed forty (40) feet.”
  • Building heightSpecified

    Buildings in the R-1 residential district inside Fenton city limits

    • Height is measured under the chapter 415 rules; height measurement method was not read.

    maximum building height: <= 40 feet

    “the maximum building height shall not exceed forty (40) feet.”
    One more reviewed finding on this topic
  • Subdividing landRegulated (with conditions)

    Subdivision of land inside Fenton city limits under the city's chapter 440 subdivision regulations

    • Chapter 440 (sections 440.010-440.290) was not opened; this claim rests on the reference to chapter 440 in the R-5 text.
    • Section 415.065 requires R-5 developments to meet chapter 440 in addition to the zoning rules.
    “any development in the "r-5" district shall be subject to all of the terms, conditions, and requirements of the subdivision regulations under chapter 440”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission; ask Fenton or St. Louis County directly.

  • Building permit — New construction and alterations inside Fenton city limits
  • Owner-builder exemption — Owner-built home inside Fenton city limits
  • Inspections — Inspections of new construction inside Fenton city limits
  • Certificate of occupancy — Occupancy of a new home inside Fenton city limits
  • Minimum dwelling size — Minimum floor area of a single-family dwelling inside Fenton city limits
18 more unanswered
  • Lot coverage
  • Living in an RV
  • Camping on your land
  • Tiny homes
  • Manufactured homes
  • Accessory dwellings
  • Who permits septic
  • Septic permit
  • Septic inspection
  • Off-grid sanitation
  • Well permit
  • Mandatory utility hookup
  • Agricultural exemption
  • Driveway access
  • Building in a floodplain
  • Short-term rentals
  • Permit fees
  • Permit process

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 Fenton publishes no rule on the point, not that none exists. St. Louis County’s page lists the county offices to call.

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