Bolthole Index

St. Charles County, Missouri

Building permits, zoning and septic rules in Foristell, Missouri

Foristell, Missouri requires a building permit for a new home; the City’s Building Commissioner handles plan reviews and inspections.1 Foristell sets its own zoning, including district-specific lot and dwelling sizes.234 St. Charles County issues private septic permits inside Foristell, even when the property lies in another county.5

At a glance

Building permits
Required for new homes, decks, sheds, pools, basement finishes, additions and major alterations1
Zoning
Foristell administers its own zoning2
Private septic
St. Charles County permit required before construction, throughout Foristell5
Minimum lot size
AG-1: 10 acres per single-family residence; R-1: 3 acres and 150-foot minimum width63
Minimum home size
R-1: 1,800 square feet single-story, 2,200 story-and-a-half, 2,400 two-story4
Floodplain development
Floodplain development permit required in designated floodplain areas7

Who to call

Building permits

City of Foristell Building Commissioner

City building permit applications, plan reviews, inspections and occupancy questions; ask this office to identify the municipal floodplain contact.

(636) 463-2123 ext. 102

[email protected]

121 Mulberry Street Foristell, MO 63348

Online permits →

Zoning

City of Foristell Planning & Zoning Commission / City Hall

Starting contact for zoning district confirmation, lot requirements and proposed land uses.

(636) 463-2123

[email protected]

121 Mulberry Street Foristell, MO 63348

Septic permits

St. Charles County Building and Code Enforcement Division

Private sewage disposal system permits and inspections inside Foristell under the City sewer code.

636-949-7345

[email protected]

201 N. Second St. Suite 412 St. Charles, MO 63301

Contact details are copied from each office’s official page and were checked against it on October 12, 2026.

Off-grid gear

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

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Do you need a building permit in Foristell, MO?

Foristell requires building permits for new homes, decks, sheds, pools, basement finishes, additions and major alterations.1 Foristell has adopted the 2021 International Building Code, subject to the amendments and exemptions in its building-code chapter.8 Start with the City’s Building Commissioner for the proposed work and application requirements.1 We could not confirm a Foristell owner-builder exemption; ask the Building Commissioner before assuming that doing the work yourself removes the building permit requirement.1

Who issues building permits in Foristell, and how do you apply?

The Foristell Building Commissioner performs plan reviews and inspections on new residential and commercial properties; reach the office at (636) 463-2123 ext. 102 or [email protected].1 Use the City’s linked citizen portal to begin a building permit application.1 Foristell requires a site plan showing building location, lot dimensions, easements, grades, drainage and any well, septic system and drain field.1 Construction plans must show elevations and construction details, including foundation, floor plan, electrical, plumbing and mechanical plans.1

Does Foristell have zoning, and what lot and home sizes apply?

Foristell administers its own zoning inside city limits, so identify the parcel’s district before choosing a house plan.2 In Foristell’s AG-1 Agricultural District, each single-family residence needs at least 10 acres.6 AG-1 requires at least 1,000 square feet for a single-story dwelling and states a 700-square-foot minimum for each floor over one.9 In Foristell’s R-1 Residential District, the minimum lot is 3 acres with a minimum width of 150 feet.3 R-1 dwelling minimums are 1,800 square feet for single-story, 2,200 for story-and-a-half and 2,400 for two-story homes.4 Ask Foristell City Hall to confirm the parcel’s district and applicable setbacks before committing to a site layout.10

How do septic permits work inside Foristell?

Before constructing a private sewage disposal system inside Foristell, the owner must obtain a permit from St. Charles County, regardless of which county contains the property.5 Contact the St. Charles County Building and Code Enforcement Division for septic permit questions.11 Foristell’s sewer code requires notification to St. Charles County for final inspection before underground portions are covered.12 Foristell’s final building inspection or certificate of occupancy also depends on fire protection district approval and, where applicable, St. Charles County’s final septic inspection approval.1 Arrange the septic review alongside the house plans, rather than leaving wastewater approval until construction is complete.51

Can you live in an RV or tiny home in Foristell?

We could not confirm Foristell’s general rules for long-term RV occupancy, temporary camping or accessory dwelling units; ask City Hall about the proposed use and parcel’s zoning district before buying land for that purpose.10 Foristell’s dwelling-size requirements are a concrete constraint on a small conventional home: R-1 requires at least 1,800 square feet for a single-story dwelling.4 AG-1 has a lower single-story minimum of 1,000 square feet, but each single-family residence requires at least 10 acres.96 Those district requirements do not establish a separate tiny-home permission; request a determination for the actual design and occupancy plan from Foristell City Hall.10

What are the steps to building a home in Foristell?

  1. Confirm Foristell city limits and the parcel’s zoning district with City Hall; use the St. Charles County guide for land outside city limits, where county zoning applies in unincorporated areas.1013
  2. Match the house and lot to the Foristell district’s dimensional requirements, and ask City Hall about setbacks and any proposed subdivision.631410
  3. Prepare site and construction plans for the City’s building permit application, including any well, septic and drain-field locations.1
  4. Obtain St. Charles County’s private septic permit before system construction, if private sewage disposal is proposed.5
  5. Ask the Building Commissioner about floodplain review; Foristell requires a floodplain development permit in designated floodplain areas.17
  6. Coordinate inspections and obtain the applicable fire district and septic final approvals before requesting the City’s final inspection or certificate of occupancy.1

What should you check before buying land in Foristell?

Ask Foristell City Hall to confirm the parcel’s zoning district, setbacks and proposed residential use before treating an advertised acreage as a buildable homesite.10 Foristell regulates subdivisions and land development separately from its zoning districts, so ask about any planned split as well.1410 We could not confirm Foristell’s private-well or driveway-access requirements; ask the Building Commissioner which approvals the proposed site needs.1 For an existing structure, Foristell requires an occupancy inspection whenever ownership, tenancy or occupancy changes.1 For a new home with private sewage disposal, account for both the City’s building approval and St. Charles County’s septic approval in the purchase conditions.15

Watch-outs

  • Foristell’s AG-1 minimum is 10 acres per single-family residence; R-1 has a different 3-acre minimum, so acreage alone does not establish the applicable district.63
  • Foristell assigns private septic permits to St. Charles County even when a Foristell parcel is located in another county.5
  • An existing Foristell structure needs an occupancy inspection upon a change of ownership, tenancy or occupancy.1

Sources

  1. City of Foristell Building Commissioner (cityofforistell.org)
  2. City of Foristell, MO Code of Ordinances (Foristell), quoted and re-checked
  3. Article IV: Zoning District Regulations (Foristell), quoted and re-checked
  4. Article IV: Zoning District Regulations (Foristell), quoted and re-checked
  5. Chapter 710: Public and Private Sewers (Foristell), quoted and re-checked
  6. Article IV: Zoning District Regulations (Foristell), quoted and re-checked
  7. Chapter 415 Floodplain Management (Foristell), quoted and re-checked
  8. Article II: Building Codes (Foristell), quoted and re-checked
  9. Article IV: Zoning District Regulations (Foristell), quoted and re-checked
  10. City of Foristell Planning & Zoning Commission / City Hall (cityofforistell.org)
  11. St. Charles County Building and Code Enforcement Division (sccmo.org)
  12. Chapter 710: Public and Private Sewers (Foristell), quoted and re-checked
  13. Unified Development Ordinance, quoted and re-checked
  14. Chapter 410 Subdivision and Land Development Regulations (Foristell), quoted and re-checked

Written October 12, 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 Foristell

Foristell’s own rules

  • Building code adoptedAdopted

    Building construction inside Foristell city limits.

    • The adopted code is subject to the amendments and exemptions in Chapter 500.

    building code edition: 2021 International Building Code (including Appendices C, E, F, G and H, except as otherwise provided in Chapter 500)

    “The 2021 Edition of the International Building Code [...] is adopted by reference as the Building Code of the City”
  • InspectionsRequired

    Installations subject to inspection under the City-adopted building and plumbing codes inside Foristell city limits.

    • The authority having jurisdiction must be notified when the installation is ready for inspection.
    • The inspection is to be conducted within two business days.

    inspection deadline: 2 business days

    “The authority having jurisdiction shall be notified when the installation is ready for inspection and shall conduct the inspection within two (2) business days.”
  • Local zoningPresent

    Land inside Foristell city limits; the City adopts and administers its own zoning regulations.

    • The code is published as including legislation through 2024-06-03.
    “Chapter 400 Zoning Regulations (Section 400.010 – Section 400.390)”
  • Zoning districtsPublished

    Zoning districts inside Foristell city limits.

    • The article lists AG-1, R-1 through R-5, PD, C-1 through C-3, M-1 through M-3, MUDD, Mobile Homes and Mobile Home Parks, Park/Recreational/Scenic, and Special Old Town districts.
    “Section 400.130 "AG-1" Agricultural District. Section 400.140 "R-1" Residential District.”
  • Minimum dwelling sizeSpecified

    Single-family dwellings in the AG-1 Agricultural District.

    • The AG-1 single-family dwelling must be on at least ten acres.
    • The district provides separate minimums for single-story and multistory dwellings.

    single-story dwelling size: >= 1000 square feet · each floor over one floor: >= 700 square feet

    “Dwelling size. Minimum one thousand (1,000) square feet for single story. Minimum seven hundred (700) square feet for each floor over one (1).”
    One more reviewed finding on this topic
    • Specified — Single-family dwellings in the R-1 Residential District.
      “Dwelling size. Minimum eighteen hundred (1,800) square feet for a single story, twenty-two hundred (2,200) square feet for a story and a half and twenty-four hundred (2,400) for a two-story dwelling.”
  • Minimum lot sizeSpecified

    Single-family residences in the R-1 Residential District.

    • The district also requires a minimum lot width of 150 feet.

    minimum lot area: >= 3 acres · minimum lot width: >= 150 feet

    “Lot Area. Minimum of three (3) acres. [...] Lot width. Minimum width of one hundred fifty (150) feet.”
    One more reviewed finding on this topic
    • Specified — Single-family residences in the AG-1 Agricultural District.
      “Lot Area. Single-family residences — minimum ten (10) acres for each single-family residence.”
  • Building heightSpecified

    Structures in the AG-1 Agricultural District.

    • The source states a general maximum for structures.

    maximum structure height: <= 35 feet

    “Height Limitations. No structure may exceed thirty-five (35) feet.”
    One more reviewed finding on this topic
  • Who permits septicCounty

    Private sewage disposal systems inside Foristell city limits; St. Charles County is the permitting and inspection authority even when the property is located in another county.

    • The City code also incorporates City, county, Missouri Department of Natural Resources, and Missouri Department of Health and Senior Services requirements.
    “Before commencement of construction of a private sewage disposal system, the owner shall first obtain a permit from St. Charles County regardless of what County the property is located in.”
  • Septic inspectionRequired

    Private sewage disposal systems inside Foristell city limits.

    • The St. Charles County Inspector may inspect at any stage.
    • The applicant must notify St. Charles County for final inspection before underground portions are covered.
    • The permit is not effective until installation is completed to St. Charles County's satisfaction.
    “the applicant for the permit shall notify St. Charles County when the work is ready for final inspection and before any underground portions are covered.”
  • Subdividing landRegulated (with conditions)

    Subdivision and land development inside Foristell city limits.

    • The code separately identifies major subdivisions, minor subdivisions, preliminary plats, record plats, development agreements, and development standards.
    “Chapter 410 Subdivision and Land Development Regulations”
  • Building in a floodplainRequired

    Development in designated floodplain areas inside Foristell city limits.

    • The chapter applies according to its lands-to-which chapter applies provision; the reviewed page identifies the permit requirement but not parcel-specific floodplain status.
    “Section 415.110 Floodplain Development Permit (Required).”

Still unanswered

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

  • Building permit — Building permits for construction inside Foristell city limits.
  • Owner-builder exemption — Owner-builder work inside Foristell city limits.
  • Certificate of occupancy — Certificates of occupancy inside Foristell city limits.
  • Lot coverage — Lot coverage for residential districts inside Foristell city limits.
  • Living in an RV — Residential or long-term recreational-vehicle occupancy inside Foristell city limits.
7 more unanswered
  • Camping on your land
  • Tiny homes
  • Accessory dwellings
  • Well permit
  • Agricultural exemption
  • Driveway access
  • 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 Foristell publishes no rule on the point, not that none exists. St. Charles County’s page lists the county offices to call.

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