How to Get a HVAC Permit in St. Louis, MO (2026 Guide)
Everything you need to know about hvac permits in St. Louis, MO, local requirements, fees, timelines, and how to apply.
By Joey, Founder · Last updated May 23, 2026 · How we research →
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Free Permit Lookup →Do You Need a HVAC Permit in St. Louis?
Based on St. Louis's local building codes, you'll need a permit when:
Replacing an HVAC system (even same-for-same) requires a mechanical permit.
Installing a new HVAC system requires mechanical and possibly electrical permits.
Modifying or installing ductwork requires a mechanical permit.
Installing a mini-split system requires mechanical and electrical permits.
Permit Fees in St. Louis
Based on local St. Louis permit data, fees for hvac projects typically range:
Here's how fees break down by project scope nationally:
| Project Scope | Typical Permit Fee |
|---|---|
| Furnace or AC replacement | $75 – $300 |
| Heat pump installation | $100 – $350 |
| Mini-split installation | $75 – $250 |
| New ductwork | $100 – $400 |
| Gas line permit (separate) | $50 – $200 |
| Electrical permit (if needed for new circuits) | $50 – $200 |
Fees are typically calculated based on estimated project value. Contact Building Division - Permits Section for exact amounts.
How Long Does It Take?
In St. Louis, typical approval time for hvac permits is about 1 week.
More complex projects requiring structural review or variances may take longer. Simple projects may qualify for expedited or over-the-counter review in some cases.
How to Apply for a HVAC Permit in St. Louis
- 1 Check requirements: Use our free lookup tool or contact Building Division - Permits Section to confirm your project needs a permit.
- 2 Gather documents: Prepare your application, site plan, construction drawings, and any other required documents.
- 3 Submit online: St. Louis accepts applications online at Building Division - Permits Section.
- 4 Pay fees: Pay the applicable permit fees ($75 – $500).
- 5 Wait for approval: Your application will be reviewed by St. Louis plan reviewers. Typical turnaround is about 1 week.
- 6 Begin work: Once approved, post your permit visibly at the job site before starting work.
- 7 Schedule inspections: Call Building Division - Permits Section at (314) 622-3315 to schedule required inspections at each phase of the project.
St. Louis Building Department Contact
Required Inspections in St. Louis
Most hvac projects in St. Louis require inspections at each construction stage:
Rough-In Mechanical Inspection (new ductwork), Duct sizing and support/hanging, duct sealing at all joints (mastic or UL 181-rated tape), return air pathways, equipment location clearances, combustion air provisions per IRC G2407, and condensate drain routing.
Gas Piping Pressure Test, Gas piping system pressurized (typically 3 PSI for 10 minutes or per local code) with no pressure drop, indicating no leaks. Inspector witnesses the test or verifies documented results. Proper sediment trap (dirt leg) installed ahead of each appliance.
Final Mechanical Inspection, Equipment installed per manufacturer instructions, gas connections tight and leak-tested, venting is correct material with proper slope and termination clearances, condensate drainage functional, thermostat operation verified, CO detectors installed (required in many jurisdictions near gas appliances), system fires up and operates correctly, clearance to combustibles maintained, filter accessible, and equipment nameplate matches the permit.
Schedule inspections with Building Division - Permits Section at (314) 622-3315 at least 24–48 hours in advance.
Frequently Asked Questions
Whether you need a permit depends on the size and scope of your hvac project. In St. Louis, some smaller projects are exempt while larger ones require a permit. Use our free lookup tool to check your specific situation.
Permit fees for hvac projects in St. Louis typically range from $75 – $500. Fees are usually based on the estimated project value.
Typical approval time in St. Louis is about 1 week. Complex projects requiring structural review may take longer.
In most cases, homeowners in St. Louis can pull permits and perform work on their own primary residence as an owner-builder. You're still responsible for meeting all code requirements and passing inspections.
Working without a required permit in St. Louis can result in fines, stop-work orders, required removal of completed work, and complications when selling your home.
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Free Permit Lookup →Other Permit Guides for St. Louis, MO
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See Detailed HVAC Rules for St. Louis
View all local rules, exemptions, and fee details on the permit page.
HVAC Permit Rules →