How Much Does a Building Permit Cost in St. Louis County?

Permit Cost by Project

Do You Need a Permit?

St. Louis County breaks everything into separate trade permits. You don't get one nice bundle. A typical bathroom remodel around $15,000 runs $431 total. That covers the building permit at $208, electrical at $106, plumbing at $47 and HVAC at $94. I had to cross reference three PDFs plus the 2025 ordinance to nail these down. Meanwhile, the building permit itself doesn't scale aggressively with project cost. It sits at $188 for $8,000 work and only reaches $232 at $25,000. Kitchen remodels land near $385 to $465 depending on scope. A roof replacement comes in at $208. And yet these numbers come from the fee tables in Chapter 1100 of the county code. (The formula isn't published cleanly. We ran the exact benchmarks against the ordinance tables.) Reinspection fees hit $47 each time. Extension fees are also $47. Nothing here's cheap once you add every trade. The calculator on this page lets you plug in your project size and see the real number. Most homeowners underestimate by at least a couple hundred bucks. Plan for it up front.

You need a permit for most work that touches structure, systems or safety. Do I need a permit in St. Louis County to replace a roof? Yes. Do I need a permit in St. Louis County to remodel a bathroom? Almost always. Same for finishing a basement, building a deck or installing an EV charger. The county exempts quite a few small jobs though. Sheds 50 square feet or smaller don't need one. Fences six feet or shorter are clear. Replacement windows are exempt if you don't change the rough opening. Same deal for doors, basic painting, flooring and trivial grading under 30 cubic yards. But don't assume your project qualifies. The exemptions sit in the 2023 Ordinance Guidebook. They tightened the shed threshold below the standard IRC rules. Check before you start. Skipping the permit on required work creates real problems later. But here's the thing, the building department won't be shy about it.

The county doesn't publish specific penalty multipliers in the fee ordinance we reviewed. That doesn't mean they ignore violations. Code enforcement finds unpermitted work through complaints, property sales and visible jobs. When they do, you usually pay retroactive fees plus extra. Stop work orders are prevalent. You can't sell the house cleanly with open violations either. The lack of clear penalty language in Ordinance 29,445 surprised me. Most cities spell it out. Here the documents stay quiet. Still, nobody wins by gambling. Pull the permit. The fees aren't outrageous enough to justify the risk. Get it on record and sleep better.

Permit duration details aren't spelled out in the main fee documents. You can get extensions though. The extension fee runs $47. Same price for a permit application extension. The exact inactivity or abandonment period was not listed in the tables we found, so verify that window with the county before you rely on a timeline. Plan your schedule tight. File early. Don't let the permit sit idle. If you need more time, pay the $47 and request the extension before it expires. Plain enough. But you have to stay on top of it.

Your contractor should pull the permits. Not you. That's the standard advice here like everywhere else. Still, the county doesn't publish clear owner-builder rules in the fee ordinance. We couldn't find specific homeowner language. This creates gray area. Licensed contractors carry insurance and take responsibility for code compliance. If they ask you to pull it yourself, treat that as a red flag. Make sure the contract says they handle all permits. Follow up to confirm they actually filed. I've seen too many projects stall because this step got ignored.

St. Louis County stands out because it requires separate permits for every trade. Building, electrical, mechanical and plumbing each get their own paperwork under Chapter 1100. Sections 1100.060, 1100.140, 1100.190 and 1100.200 lay it out. One $15,000 bathroom can trigger four distinct permits and four different fees. The building department doesn't bundle them. This adds up. A kitchen job at $25,000 hits $465 once you pay every piece. The structure feels bureaucratic. Yet the individual fees stay reasonable. No state surcharge on top either. We pulled the 2025 amendment to Ordinance 29,445 and the older 2020 version to confirm nothing changed on this point. Point taken. It forces you to think in trades, not one big project cost. Worth knowing before you start tearing out walls.

How much does a building permit cost in St. Louis County?

A building permit in St. Louis County costs $188 on an $8,000 project and $232 on a $25,000 project. Add the separate trade permits and a bathroom remodel around $15,000 runs about $431 total. Use the calculator on this page for your exact scope.

Do I need a permit to replace a water heater in St. Louis County?

Yes. A water heater replacement needs a plumbing permit. It costs $47 in St. Louis County. Don't skip it. The county requires permits for this work even though many homeowners assume it's exempt.

Do I need a permit to build a deck in St. Louis County?

Yes. Deck construction requires a building permit. Expect to pay $208 on a customary $12,000 project. The county doesn't exempt decks even if they sit low to the ground.

How much is a plumbing permit in St. Louis County?

A basic plumbing trade permit starts at $47. On a full bathroom remodel you'll pay this amount in addition to the building, electrical and mechanical permits. The county charges each trade separately.

Why does St. Louis County require so many separate permits?

Chapter 1100 of the county code requires individual permits for building, electrical, mechanical and plumbing work. Ordinance No. 29,445 kept this structure in the 2025 update. One project can trigger four permits and four fees. The county doesn't offer a single combined permit.