Zoning, building permits and septic rules in Clayton, Missouri
Clayton is a city in St. Louis County, Missouri. Clayton adopts its own zoning, so inside its limits Clayton’s rules apply, not the county’s. 7 rules below are quoted from official sources and independently re-checked, most recently on October 23, 2026. Rules for unincorporated land are on the St. Louis County page.
Answers from the rulebook for Clayton
Clayton’s own rules
Building permitLimited
Small listed work inside Clayton city limits, including one-story detached tool or storage sheds not over 50 sq ft
Exemptions do not authorize work that violates the building code, the zoning ordinance, or other city laws.
Retaining walls over 4 feet need a permit; all front-yard retaining walls require architectural review board approval.
Sidewalks and driveways are exempt only if outside the public right-of-way, not over 30 inches above grade, not over a basement or story below, and not part of an accessible route.
Other listed exemptions include finish work, temporary sets, prefabricated pools under 24 inches deep, and playground equipment in a rear yard.
accessory shed gross floor area maximum: <= 50 sq ft (one-story detached tool and storage sheds, playhouses and similar uses) · retaining wall height maximum for exemption: <= 4 ft (measured from bottom of footing to top of wall, unless supporting a surcharge)
“permits shall not be required for the following: building: 1. one-story detached accessory structures used as tool and storage sheds, playhouses and similar uses, provided the gross floor area does not exceed fifty (50) square feet.”
Building code adoptedAdopted (with conditions)
All construction inside Clayton city limits under the city building code
Adopts the 2021 International Building Code, Mechanical, Plumbing, Residential, Fuel Gas, Energy Conservation, Existing Building, and Swimming Pool and Spa codes, with local additions in section 500.020.
Electrical code is adopted separately at section 500.030 (not opened).
“the building code of the city shall consist of part i, the 2021 international building code, part ii, the 2021 international mechanical code”
InspectionsLimited
Non-residential premises before occupancy inside Clayton city limits
Inspection is tied to the certificate of occupancy; general inspection schedule for residential work was not confirmed.
“no such certificate shall be issued unless said premises has been inspected by the code official and the premises is in compliance with this code and all zoning regulations.”
Certificate of occupancyRequired
Non-residential structures inside Clayton city limits only; residential occupancy rule not established
Certificate is issued only after code-official inspection and confirmation of compliance with the building code and all zoning regulations.
An occupancy permit becomes invalid after 90 days if premises are not occupied by the authorized tenant, and none may issue if more than 90 days have passed since inspection (section 113.3.2).
“section 113.3 occupancy permits, non-residential structures: it shall be unlawful for any person, owner or operator to occupy or use or to permit occupancy or use of any premises for any purpose until a certificate of occupancy has been issued by the code official.”
Local zoningPresent (with conditions)
Land inside Clayton city limits: the city publishes its own zoning ordinance as Chapter 405, Zoning Regulations, of its code.
The chapter title and section range are taken from the official code table of contents; district-level standards were not opened (see zoning_districts claim).
“chapter 405 zoning regulations (section 405.010”
Zoning districtsPartial
Land inside Clayton city limits
Only the chapter structure is confirmed: Chapter 405 Zoning Regulations and Chapter 410 Overlay and Urban Design Zoning Districts. The individual district list and boundaries were not opened.
“chapter 410 overlay and urban design zoning districts (section 410.005”
Subdividing landRegulated (with conditions)
Land divisions inside Clayton city limits
Chapter 415 Subdivision Regulations exists in the city code; its substantive standards were not opened.
We looked and could not find an official answer yet. Silence is not permission; ask Clayton or St. Louis County directly.
Owner-builder exemption — Owner-builder exemption inside Clayton city limits
Minimum dwelling size — Minimum dwelling size, main single-family residential district, inside Clayton city limits
Minimum lot size — Minimum lot size, main single-family residential district, inside Clayton city limits
Setbacks — Setbacks, main single-family residential district, inside Clayton city limits
Lot coverage — Lot coverage, main single-family residential district, inside Clayton city limits
18 more unanswered
Building height
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 Clayton publishes no rule on the point, not that none exists. St. Louis County’s page lists the county offices to call.
Off-grid gear
Going off-grid in Clayton means bringing your own water and power. The kit we’d start with:
