Do I need a permit for a full bathroom remodel in
O'Fallon, Missouri?

O'Fallon full bathroom remodel permits — the key details

The threshold for a permit in O'Fallon is simple: if you're moving a fixture (toilet, sink, shower valve, vent line) or adding a new circuit, you need a permit. If you're replacing a toilet, sink, or faucet in the existing location without any drain or supply-line changes, or if you're ripping out an old vanity and installing a new one in the same footprint, no permit is required. The confusion arises when homeowners assume that 'major remodel' automatically means permit, or that cosmetic changes never need one. Reality: it's fixture-location-based, not scope-based. A 'full gut' that keeps all plumbing fixtures in their original locations might not need a permit; a 'cosmetic remodel' that moves the toilet 2 feet to the wall definitely does. O'Fallon Building Department staff can confirm via phone or email whether your specific scope is exempt, and this call takes 10 minutes and saves thousands of dollars in fines or remediation.

Electrical is the second critical gateaway. If you're adding a new exhaust fan, a heated towel rack, a ventilation fan, a GFCI outlet, or a second light circuit, you need an electrical permit and plan. O'Fallon enforces NEC 210.8(A)(1): all receptacles within 6 feet of a sink (including guest baths and powder rooms) must be GFCI-protected. The code also requires AFCI protection on bedroom branch circuits and living spaces per NEC 210.12, though bathrooms themselves don't require AFCI—only GFCI. A frequent rejection during rough electrical inspection is the absence of a label showing which outlets are GFCI-protected or GFCI-fed. The electrical plan must clearly indicate whether you're using individual GFCI outlets or a GFCI circuit breaker. O'Fallon inspectors will not pass rough electrical without this annotation. If you're hiring a licensed electrician, they'll handle this automatically; if you're doing the work yourself (permitted in O'Fallon for owner-occupied homes), you must include an electrical diagram with your permit application or expect a plan-review rejection and a 1–2 week delay.

Plumbing and drainage rules are strict under the Missouri State Building Code adoption of the 2015 IPC (International Plumbing Code). If you relocate a toilet, sink, or shower drain, you must ensure that the new vent line does not exceed 42 inches horizontal between the trap and the vent entry point (IRC P3105.1)—a rule that trips up DIY relocations. Shower and tub drains must also slope at least 1/4 inch per foot; if your concrete slab is settling or uneven, you may need to address this during rework. Trap arms (the horizontal section of pipe between the trap outlet and the vent) cannot exceed 3 feet for a toilet or 2.5 feet for a sink; exceeding this requires an additional vent stack, which adds cost and may not be feasible in a tight bathroom. The rough plumbing inspection in O'Fallon requires the inspector to verify all of these dimensions and test the drainage slope with a level. Many contractors who relocate a toilet don't realize they need to re-slope the drain or add a vent, discover this during inspection, and must tear out drywall to remediate—adding 2–4 weeks and $2,000–$5,000 in extra cost.

Waterproofing for showers and tubs is governed by IRC R702.4.2, which requires a water-resistant or waterproof membrane behind tile in shower and tub surrounds. O'Fallon's building inspector will ask on your permit application what waterproofing system you're using: cement board plus liquid membrane, fiber-reinforced panel, or a pre-sloped shower base. If you don't specify, plan review will flag this as incomplete and ask for clarification, adding 1 week to the timeline. Some builders use older cement-board-only systems without a liquid membrane, which no longer meets code; the city will require an upgrade. The rough framing inspection often occurs before rough plumbing, so the inspector will verify that the shower/tub rough-in is in place and that adequate blocking is provided for grab bars (required in many jurisdictions, though O'Fallon's local amendment on this should be confirmed with the building department). If you're converting a tub to a shower or vice versa, the waterproofing requirement changes: showers with exposed tile (floor or surround) require a full water-resistant membrane, while bathtub surrounds below the showerhead do not. This distinction matters during plan review.

The permit and inspection timeline in O'Fallon typically spans 3–5 weeks from application to final sign-off. The first 1–2 weeks are plan review: the building department reviews your permit application, electrical plan, and plumbing plan for code compliance. Common rejections are lack of GFCI notation on the electrical plan, missing waterproofing specification, or trap-arm length exceeding code. Once the plan is approved, you schedule rough inspections (rough plumbing and rough electrical, often on the same day or back-to-back). After rough inspections pass, you proceed to drywall and finish. The final inspection occurs after all work is complete and the bathroom is functional. If you're an owner-builder in O'Fallon, you can file the permit application yourself, but you must inspect the work yourself or hire a licensed inspector; the building department will not sign off without an inspection. Hiring a licensed contractor (plumber and electrician for the respective trades) is recommended if you're not experienced, as inspection failures delay the project by 1–2 weeks per rejection.

Three O'Fallon bathroom remodel (full) scenarios

O'Fallon's GFCI and electrical circuit requirements for bathrooms

The National Electrical Code (NEC 210.8(A)(1)) requires that all receptacles within 6 feet of a sink, bathtub, or shower in a bathroom must be GFCI-protected. O'Fallon adopts this rule without local amendment, so it applies strictly. The 6-foot measurement is horizontal from the inside edge of the bathtub or the sink basin. Many homeowners and even some contractors misunderstand this: a outlet 6 feet away from a sink is not protected, but one 5.9 feet away must be. In a typical 5-by-8-foot bathroom with a toilet and sink on one wall and a shower on another, nearly all outlets fall within the 6-foot radius of either the sink or shower, meaning they all must be GFCI-protected. The protection can be provided in two ways: (1) install individual GFCI receptacles (cost: $20–$40 per outlet), or (2) install a GFCI circuit breaker in the main panel, which protects all outlets on that circuit (cost: $40–$80 per breaker, plus labor). Most contractors use a GFCI circuit breaker for bathroom circuits because it's cheaper and protects all outlets downstream. On your electrical plan submitted with the permit application, you must clearly indicate which method you're using and label the outlets accordingly. O'Fallon's inspector will not pass rough electrical without this notation. If you submit a plan that says 'standard outlets' with no GFCI annotation, plan review will reject it with a request for clarification, adding 1 week to the timeline. If you're doing the work yourself, measure carefully, count outlets within the 6-foot radius, and either buy GFCI outlets or provide a detail showing the GFCI breaker in the panel.

Waterproofing systems and shower/tub conversions in O'Fallon bathrooms

IRC R702.4.2 mandates a water-resistant barrier behind tile in shower and tub surrounds. O'Fallon enforces this strictly during rough plumbing inspection, before drywall goes up. The barrier must extend from the base of the tub or floor of the shower to at least 6 inches above the showerhead (or to the ceiling if the shower is open). For showers with a sloped floor (traditional pan or base), a waterproof membrane or pan liner is required under the tile; for tub surrounds below the showerhead, a water-resistant membrane (such as cement board with liquid waterproofing) is acceptable. Many older homes in O'Fallon have cement-board-only systems with no liquid membrane, which fail inspection today. The city will require you to upgrade to a full membrane system—typically a 2-layer approach: (1) cement board, then (2) liquid waterproofing membrane (such as Redgard, Kerdi, or equivalent), then tile. Fiber-reinforced cement boards (like Durock or HardieBacker) are also acceptable if used with a liquid membrane. Pre-sloped shower bases (prefabricated units) that include an integral pan are often waived from the additional membrane requirement if the manufacturer's data sheet is provided to the building inspector. If you're converting a bathtub to a shower, the waterproofing requirement increases because the entire shower stall must be waterproofed. The plan review stage is when to specify which system you're using; if you leave this blank, expect a rejection. If you're an owner-builder, consult the building department's FAQ or call ahead to ask which specific products the inspector prefers—some inspectors have preferences, and checking in advance saves a punch-list rejection.

Common questions