What's Required in St. Louis
- Mechanical permit before any mechanical work, including furnace, heat pump, condenser and mini-split replacements (Mechanical Code 106.1; 2018 IMC as adopted by Ord. 70800)
- No permit for portable heating, cooling, ventilation or cooking appliances, or for replacing a minor part that does not alter the equipment's approval
- Fees: $25 application plus $40 per furnace, $40 per condensing unit, $40 per combination furnace and condensing unit; $50 for failing to request an inspection; $25 re-inspection
- Permit issued only to a mechanical contractor licensed by the City of St. Louis Building Division holding a City business license, or to an owner-occupant under the Homeowners Permit exception
- Homeowner installs that involve refrigerant require EPA Universal Technician certification (40 CFR Part 82, Subpart F)
- Electrical permit ($25 + $60) for any new circuit or disconnect, by a city-licensed electrical contractor or tested owner-occupant
- Application filed online at stlcitypermits.com; emergency replacements may begin once the application is submitted
- A copy of the permit kept on site until the work is complete and inspected
Do You Need a Permit to Replace a Furnace or AC in St. Louis?
Yes. The city's Mechanical Code (2018 IMC as adopted by Ordinance 70800, codified at 25.03.020) says no person shall commence any mechanical work until a permit for such work has been issued, and the Building Division's page says mechanical permits are required to install things like boilers, furnaces, exhaust fans and hoods, and ventilation systems. Its residential fee table prices exactly the common jobs: a furnace, a condensing unit, or a combination furnace and condensing unit. What needs no permit is listed in Section 106.2: portable heating, cooling, ventilation and cooking appliances, and the replacement of any minor part that does not alter the approval of the equipment. So a capacitor, igniter, control board or thermostat is a repair; a new furnace, heat pump, condenser or mini-split is permit work. Emergency replacements may start once the application has been filed online.
One wrinkle to know: an older chapter of the Revised Code (25.10.500, from 1992) still says minor repairs or replacements in an existing system up to $25,000 need no permit application. The 2018 Mechanical Code adopted later requires a permit for any mechanical work and prices furnace and condenser installs, and the Building Division's pages follow the newer code. Treat an equipment swap as permit work.
St. Louis HVAC Permit Rules by Scenario
| What you are doing | City filing | Rule |
|---|---|---|
| Replacing the furnace and AC together as a matched system | Mechanical permit, $65 ($25 + $40 combination unit) | Mechanical fee table, residential |
| Furnace only, or condensing unit only | Mechanical permit, $65 ($25 + $40) | Fee table |
| Furnace and condenser billed as separate items | Mechanical permit, $105 ($25 + $40 + $40) | Fee table: furnaces, each; condensing units, each |
| New 240 V circuit or disconnect for the condenser | Electrical permit, $85 ($25 + $60), city-licensed electrical contractor or tested owner-occupant | Electrical fee table |
| Replacing a capacitor, igniter, control board or thermostat | None | Mechanical Code 106.2 item 4 |
| Window or portable units | None | Mechanical Code 106.2 items 1 and 2 |
| New ductless mini-split with its own circuit | Mechanical $65 + electrical $85 = $150 | Fee table: condensing units; electrical repair or modify |
How Much Is an HVAC Permit in St. Louis?
Every mechanical permit carries a $25 application fee. The residential lines of the fee table (Ordinance 70800, use groups R1 to R3) are $40 per furnace, $40 per condensing unit and $40 for a combination furnace and condensing unit, so a system replacement is $65 if the city bills it as a combination and $105 if it bills the two pieces separately; ask the contractor which line the Mechanical Section applies. Failing to request an inspection costs $50 per permit and a re-inspection for faulty or incomplete work is $25. If the new equipment needs a new circuit or disconnect, that is a separate electrical permit at $25 plus $60. A furnace swap with a new circuit therefore runs about $150 to $190 in city fees. Fees are paid at the end of the online application, and cards carry a 2.55 percent fee.
Who Can Pull an HVAC Permit in St. Louis?
Mechanical permits are issued to mechanical contractors licensed and certified by the City of St. Louis Building Division, and the code bars issuing one to anyone without a current City business license. The one exception is a Homeowners Permit for the owner-occupant of a single-family dwelling who shows the Mechanical Equipment Inspection Section sufficient knowledge to install the system; if the job involves handling refrigerant, the homeowner must also hold EPA Universal Technician certification under 40 CFR Part 82. In practice the installer pulls the permit from a registered trades account at stlcitypermits.com (applications are filed online under Section 106.3) or walks in at Room 425, City Hall. The Building Division says most trade permits are approved within 1 to 3 business days and all within 10, by email; the contractor then prints the permit, keeps a copy on site, and schedules the inspection from the dashboard.
What About Gas Lines, Ductwork and Energy Code?
The city adopted the 2018 International Fuel Gas Code (Ordinance 70801) and the 2018 Energy Conservation Code (Ordinance 70799) alongside the Mechanical Code, but the Building Division's pages do not say which trade permit covers a residential gas connection, and the fee table's ventilation and exhaust lines start at 200 CFM. Ask the contractor what the Mechanical Section charges for new ductwork or a gas line on your job rather than assuming it is included in the $40 equipment fee.
How to Get a HVAC Permit in St. Louis
Confirm the job is a replacement, not a repair
Minor parts (capacitor, board, thermostat) and portable units need nothing. New furnace, condenser, heat pump or mini-split: mechanical permit.
Hire a city-licensed mechanical contractor
Or qualify for the Homeowners Permit at the Mechanical Equipment Inspection Section, with EPA certification if refrigerant is handled.
Contractor applies online
From a trades account at stlcitypermits.com; the $25 application fee and $40 per unit are paid at the end. An electrician pulls a separate permit for any new circuit.
Install after approval
Most mechanical permits are approved within 1 to 3 business days by email. In an emergency, work may start once the application is submitted. Keep the permit on site.
Request the inspection
The contractor schedules it from the dashboard; failing to request one costs $50 and a faulty-work re-inspection $25.