Research by DoINeedAPermit Research Team · Updated May 2026
The Short Answer
Most HVAC work in Hazelwood requires a mechanical permit from the Building Department. The key exception: owner-occupants can handle their own replacement in owner-occupied single-family homes, but new installations, modifications, and rental properties always need a licensed contractor and permit.
Hazelwood enforces the 2018 International Energy Conservation Code (IECC) and 2018 International Mechanical Code (IMC) with specific Missouri amendments, which means HVAC work is classified as mechanical systems requiring state-licensed contractor involvement unless you're replacing equipment in your own home. Unlike some neighboring St. Louis County municipalities that have adopted older code cycles, Hazelwood's relatively recent adoption puts tighter energy-efficiency and ventilation requirements on new installations and modifications. The City of Hazelwood Building Department issues permits through their online portal or in-person at city hall. Permit fees typically run $75–$200 depending on equipment scope and valuation. A critical local distinction: Hazelwood's interpretation of owner-builder exemptions is narrower than some nearby municipalities — replacement-only work on owner-occupied single-family homes is permitted without a license, but any commercial application, rental property, modification to existing ductwork, or new installation requires a Missouri-licensed HVAC contractor (Class A or Class C mechanical license) and a filed permit with plan review and inspection.

What happens if you skip the permit (and you needed one)

Hazelwood HVAC permits — the key details

Hazelwood adopted the 2018 IMC and 2018 IECC, which govern all mechanical systems including furnaces, air conditioning, heat pumps, ductwork modifications, and ventilation equipment. The core requirement is found in IMC Chapter 1 (scope and general requirements): any HVAC installation, alteration, or repair that affects system capacity, efficiency, or safety classification requires a permit and inspection before equipment activation. For Hazelwood, this means a licensed mechanical contractor must pull the permit in the Building Department's online portal or at city hall (typically Monday–Friday, 8 AM–5 PM; confirm hours by calling ahead). The City of Hazelwood Building Department will route your application to the mechanical plan examiner, who reviews equipment specifications, ductwork sizing (per IMC 603), refrigerant piping (IMC 1102), and electrical integration. Turnaround is typically 3–5 business days for standard replacements, longer for complex modifications. Once approved, the contractor schedules a rough-in inspection (before walls close) and a final inspection (after startup). No work may begin until the permit is issued and posted at the job site.

The owner-builder exception in Hazelwood applies only to replacement of existing HVAC equipment in owner-occupied single-family dwellings, provided no ductwork is modified and the replacement is like-for-like in terms of fuel type and capacity. You cannot install a new system, convert from one fuel source to another (e.g., oil to natural gas), add ductwork, or handle the work yourself if the property is a rental, condo, or multi-family unit. Even owner-replacements require a final inspection by the Building Department to verify proper installation, clearances (per IMC 308 for furnaces: 6 inches from combustibles), and ventilation. If you attempt owner-replacement work, bring documentation proving you own the property (deed or tax bill) and call the Building Department before starting. Some inspectors will sign off on owner-performed replacement if mechanical and electrical connections are verified safe; others require a licensed contractor on all work. Clarify this by phone with the Hazelwood Building Department before proceeding.

Hazelwood's climate zone 4A (cold winter, moderate summer) drives specific code requirements that differ from warmer zones. Furnaces and heat pumps must meet minimum AFUE (Annual Fuel Utilization Efficiency) and SEER2 ratings per the 2018 IECC; as of 2024, federal minimums apply (AFUE 95% for gas furnaces, SEER2 13 for air conditioners in this zone), but Hazelwood enforces these at permit review. Ductwork in unconditioned spaces (attics, basements, crawlspaces) must be insulated to R-8 minimum (IMC 603.2.1), and any ducts in walls or floor cavities must be sealed with approved duct sealant, not duct tape. The 30-inch frost depth means outdoor condensing units must be elevated or sloped to drain away from foundations; buried condensate lines are required to slope toward a drain point. These aren't just guidelines — the plan examiner will request changes if your submittal shows inadequate insulation or drainage. Permit fees include the cost of these plan-review corrections, typically $100–$150 for a standard residential replacement.

Hazelwood's online permit portal allows contractors to upload equipment specifications (nameplate data), ductwork plans, and electrical schematics before scheduling inspections. Submittals should include the manufacturer's installation manual, AHRI (Air-Conditioning, Heating, and Refrigeration Institute) certificate (for new AC/heat pump pairs), and confirmation of electrical circuit capacity. If submitting in person, bring two copies of any ductwork sketches. The Building Department will flag missing information and return the application for revision (typically 1–2 days). Once approved, the permit is valid for 180 days; if work isn't completed within that window, you must renew the permit (usually $25–$50 additional). Inspections must be scheduled at least 24 hours in advance. Plan for two inspections: rough-in (before startup, to verify connections and clearances) and final (to confirm proper operation, pressure test of refrigerant lines, and verification of thermostat settings). Some contractors bundle these into one visit for straightforward replacements; complex modifications may require a third inspection.

One critical local detail often missed: Hazelwood requires that any HVAC contractor pulling permits carry a current Missouri State Board of Architects, Professional Engineers and Professional Surveyors (BAPSE) Class A or C mechanical license, and proof of general liability insurance ($300,000 minimum is standard). The contractor is responsible for providing this documentation to the Building Department; homeowners should request the license number and confirm it's active before signing a contract. If you hire a handyman or unlicensed technician, the permit will be denied, and you'll face a choice: hire a licensed contractor to redo the work (and pay permitting twice) or leave the system inoperable and unpermitted. Additionally, Hazelwood has adopted the 2023 Missouri Mechanical Code in some sections (e.g., heat pump efficiency standards), so equipment specifications need to reflect current minimums — a contractor using 2018-era SEER/AFUE standards may find their permit rejected. Always ask your contractor if they've pulled permits in Hazelwood recently and what code edition they're using.

Three Hazelwood hvac scenarios

Scenario A
Gas furnace replacement, 95,000 BTU, owner-occupied single-family home, north Hazelwood, no ductwork changes
You're replacing a 20-year-old gas furnace in your owner-occupied home in Hazelwood's north residential district. The new furnace is 95,000 BTU, natural-draft venting, and matches the footprint of the old unit; you're not modifying ductwork or electrical circuits. In Hazelwood, you have two paths: hire a licensed HVAC contractor to pull the permit ($75–$150), or attempt owner-replacement and request an inspection. If you go the owner route, call the Building Department ahead of time to confirm they'll inspect owner-performed work (some inspectors will, some require a contractor on site). Either way, a permit is required — and you cannot activate the furnace until the final inspection is signed off. If you hire a contractor, expect the permit to be issued in 2–3 business days; the contractor schedules rough-in (verifying clearances, venting pitch, combustion air source per IMC 303) and final (confirming thermostat operation and CO/oxygen readings). Total timeline: 5–10 business days from application to startup. Costs: permit fee $100, contractor labor $1,200–$2,500, equipment $2,500–$4,500, total project $3,800–$7,100. If you self-perform, you'll still pay the $100 permit and inspection fee (roughly $150–$200), plus equipment cost, saving the contractor labor. The Building Department will inspect to verify proper venting slope (minimum 1/8 inch per foot upward toward exit), clearance to combustibles (6 inches minimum), and electrical connections to thermostat.
Permit required (owner-occupied, replacement-only) | Permit fee $100 | Licensed contractor recommended | Final inspection required before startup | Equipment AFUE ≥95% | Total project $3,800–$7,100
Scenario B
New central air conditioning system with ductwork modification, owner-occupied home, south Hazelwood karst zone
You're adding a central AC system to an older Hazelwood home (south side, near Lindbergh Boulevard) that currently has a furnace only. You're installing a 3.5-ton outdoor condenser unit and modifying attic ductwork to integrate with the existing furnace. Because this is a NEW installation (not a replacement) and involves ductwork modification, Hazelwood requires a licensed mechanical contractor and a full permit with plan review. You cannot do this work yourself, even as owner-occupant. The contractor must submit ductwork drawings showing insulation (R-8 minimum per 2018 IMC 603.2.1), duct sealing method (UL-listed sealant, not tape), condensate drain routing, and AHRI certificate for the AC/furnace combination. Hazelwood's plan examiner will also flag the karst-zone location (south Hazelwood has sinkhole risk and variable soil settlement) — they may require verification that the outdoor unit is properly sloped or elevated to prevent water pooling and settlement-related cracking. Plan-review turnaround: 5–7 business days. Once approved, contractor schedules rough-in (ductwork pressure test per IMC 603.7 — maximum 0.5 inches W.C. leakage) and final inspection (refrigerant charge verification, subcooling measurement, thermostat calibration). Total timeline: 2–3 weeks from application to operation. Costs: permit $150–$200, ductwork fabrication and sealing $2,500–$4,000, AC unit and installation $5,000–$8,000, total $7,650–$12,200. The condensate drain must slope toward a drain point or dry well; in karst areas, the inspector may request documentation that the drain doesn't create subsidence issues. This is not typical in most areas, but Hazelwood's south-side soil conditions warrant attention.
Permit required (new installation, ductwork modification) | Contractor license mandatory (Class A or C mechanical) | Permit fee $150–$200 | Plan review 5–7 days | Two inspections required (rough-in, final) | Equipment SEER2 ≥13 | Karst-zone drainage verification may be required | Total project $7,650–$12,200
Scenario C
Refrigerant line repair and condenser coil cleaning on rental property (duplex), central Hazelwood
You own a rental duplex in central Hazelwood and the tenant reports the AC isn't cooling. You call an HVAC technician who finds a refrigerant leak in the outdoor condenser line and recommends replacing the line set and cleaning the coil. Because this is a RENTAL property (not owner-occupied), Hazelwood requires a permit and licensed contractor — no owner-builder exception applies, even for repairs. The technician must pull a permit before touching the system. The permit category is 'alteration' (not replacement), which typically costs $100–$150 and requires a brief plan review confirming the repair doesn't involve system modifications that would trigger energy-code compliance checks. However, if the repair requires replacing more than 50% of the refrigerant line (from outdoor unit to indoor coil), Hazelwood may reclassify it as a replacement and require AHRI certificate and full energy-code review — this bumps the permit fee to $150–$200 and adds 5–7 days to approval. A simple line repair and coil cleaning can be done under an 'alteration' permit in 2–3 days. Once the permit is issued, the contractor schedules a final inspection to verify the repair, refrigerant charge (proper subcooling), and system operation. Costs: permit $100–$200, technician labor (diagnosis, line replacement, pressure test) $400–$800, refrigerant (R-410A) and line material $200–$400, total $700–$1,400. Important: as the owner, you are liable to the tenant for any unpermitted repair that fails within the rental-property warranty period (typically 1 year). If you skip the permit and the system fails again, the tenant can file a habitability complaint with Hazelwood's Code Enforcement, which can result in fines ($200–$500 per day) until you correct the issue. Pulling the permit protects you and documents compliance.
Permit required (rental property, no owner-builder exception) | Alteration or replacement classification affects fee ($100–$200) | Licensed contractor mandatory | Final inspection required | 2–7 day approval timeline (depending on scope) | Tenant habitability implications | Total project $700–$1,400

Every project is different.

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Hazelwood's online permit portal and contractor licensing verification

Hazelwood's Building Department operates a permit management system accessible through the city website and mobile interface. Contractors (or homeowners, in rare owner-permit cases) log in, create a new mechanical permit application, upload scanned documents (equipment specs, ductwork sketches, electrical details), and receive a permit number within 24–48 hours if the submission is complete. The portal shows real-time status: 'Submitted', 'Under Review', 'Ready for Approval', or 'Request for Information' (RFI). If the examiner flags issues — e.g., 'SEER2 rating not listed' or 'Ductwork R-value unclear' — you'll receive an RFI with 5–10 business days to respond. Once approved, the permit PDF is downloadable and must be printed and posted at the job site. The portal also allows you to schedule inspections online (rough-in, final) and receive inspection reports.

Before hiring a contractor, verify their Missouri mechanical license via the BAPSE website (https://bapse.mo.gov) or call the agency directly at 573-751-0047. Search the contractor's name and license number; confirm the license is 'active' and hasn't expired. Class A licenses allow supervision of all mechanical systems (HVAC, plumbing, refrigeration); Class C is HVAC-only. Many contractors display their license number on their truck or website, but verify independently. Hazelwood's Building Department will not issue a permit without proof of an active license and general liability insurance (minimum $300,000). If a contractor's license is expired or suspended, the Building Department will reject the permit and recommend you hire a licensed firm. This is not a suggestion — it's a legal requirement in Missouri.

Some homeowners attempt to pull permits themselves by falsely claiming owner-builder status, or they hire a contractor who doesn't submit proper documentation. The Building Department catches this during plan review or inspection. If caught, the permit is voided, and you're subject to a $250–$500 stop-work fine plus the cost of hiring a licensed contractor to redo the work and pull a legitimate permit. You'll then pay permit fees twice (once for the rejected application, once for the legitimate one). Hazelwood Building Department staff are generally cooperative if you admit the error upfront and correct it quickly; they're far less forgiving if they discover the violation during an inspection.

Climate and code implications: 30-inch frost depth, karst zones, and energy efficiency in Hazelwood

Hazelwood's 30-inch frost depth (determined by the USDA Natural Resources Conservation Service) affects outdoor HVAC unit placement and condensate drainage. Outdoor condenser units must be elevated or sloped so that condensate — typically 3–5 gallons per day during summer operation — drains away from the foundation and doesn't create standing water. Standing water can freeze in winter, damaging the unit's base and creating subsidence in loess soil (common north of Interstate 270 in Hazelwood), or triggering sinkhole development in karst zones (south Hazelwood). The 2018 IMC 1103.2 requires condensate drainage to terminate into an approved drain or dispersal area, but Hazelwood's specific requirement is that lines must slope continuously toward the drain point (minimum 1/8 inch per 12 feet) and may not terminate where water could pool near the foundation. Contractors who bury condensate lines must slope them below the 30-inch frost line and terminate into a proper drain system, not a dry well near the house.

South Hazelwood's karst terrain (soluble limestone bedrock with sinkhole risk) means the Building Department may request additional documentation for outdoor unit placement. Karst sinkholes can develop over years or suddenly, especially if water is allowed to percolate downward. The Hazelwood Building Department may ask for a brief geotechnical note confirming the unit pad is compacted and sloped, or even a minor survey showing the unit is a minimum distance (typically 10–15 feet) from known sinkholes or limestone outcrops. This is infrequent, but if your address is in the karst zone (primarily south of Interstate 44, near Hazelwood's southern boundary), mention it to the contractor and ask if they've dealt with karst-specific requirements. North Hazelwood (loess soil) is more forgiving but still requires proper drainage to avoid settlement.

Energy-efficiency standards in the 2018 IECC adopted by Hazelwood require furnaces to meet AFUE 95% minimum and AC/heat pump systems to meet SEER2 13 minimum (as of 2024, federal standards). Some contractors spec older equipment (SEER 15 or SEER2 12.5) believing it's compliant, but Hazelwood's plan examiner will flag non-compliant equipment and request substitution. This can delay the permit by 3–5 days if the contractor doesn't have the correct model on hand. Always confirm with your contractor that all equipment meets current Hazelwood code — ask them to provide the AHRI certificate (for AC/heat pump pairs) or efficiency declaration (for furnaces) before they submit the permit application. Over-specification (e.g., high-efficiency heat pump at SEER2 16) is always acceptable and may qualify you for utility rebates or tax credits, so don't hesitate to upgrade if the upfront cost is reasonable.

City of Hazelwood Building Department
Hazelwood City Hall, Hazelwood, Missouri (confirm at city website)
Phone: Search 'Hazelwood MO Building Department phone' or call Hazelwood City Hall main line and request Building Permits | https://www.hazelwoodmo.gov (look for 'Permits' or 'Building Department' link for online portal access)
Monday–Friday, 8 AM–5 PM (verify hours before visiting; some municipalities have shortened hours or appointment-only periods)

Common questions

Can I replace my furnace myself in Hazelwood without a permit?

Only if you own and occupy the home as primary residence and the replacement is like-for-like (same fuel, capacity, no ductwork changes). Even then, you must notify the Building Department and schedule a final inspection before turning the system on. Rental properties, commercial buildings, and new installations always require a licensed contractor and permit. Call ahead to confirm the Building Department will inspect owner-performed replacement work; some inspectors require a contractor present.

How much does an HVAC permit cost in Hazelwood?

Residential permits typically range $75–$200, depending on equipment scope and whether it's a replacement (lower fee, faster review) or new installation/modification (higher fee, full plan review). Some simple replacement permits cost $100; new AC systems with ductwork changes often run $150–$200. Ask your contractor for an estimate before they submit the application.

What documents do I need to submit with an HVAC permit in Hazelwood?

At minimum: equipment nameplate data (model number, BTU, SEER/AFUE rating), AHRI certificate (for AC/heat pump pairs), and a sketch showing ductwork routing and insulation R-value if applicable. For new systems, include electrical schematics and refrigerant line routing. The contractor typically handles this; ask them to confirm the Building Department has received all documents before the permit is marked 'approved'.

How long does Hazelwood take to approve an HVAC permit?

Standard replacements with complete submittals: 2–3 business days. New installations and complex modifications: 5–7 business days for plan review. If the examiner requests information (RFI), add 5–10 days. Plan accordingly — don't expect to start work the day after applying. Many contractors bundle the application and inspection scheduling to keep projects moving.

What if the contractor's license is expired or suspended?

Hazelwood will not issue a permit. Verify the contractor's Missouri Class A or C mechanical license via BAPSE (https://bapse.mo.gov) before signing a contract. If you discover it's expired after hiring them, find a licensed contractor immediately and start over. The Building Department is firm on this — no exceptions.

Do I need a permit for routine HVAC maintenance (filter, cleaning)?

No. Routine maintenance — replacing filters, cleaning coils, topping up refrigerant (without line replacement) — does not require a permit. However, if the technician finds a leak requiring line replacement or a major repair affecting system configuration, that work does require a permit. Ask your technician upfront if any repair work will involve alterations to the system.

Can I change my furnace from natural gas to propane without a permit?

No. Converting between fuel sources (gas to propane, oil to gas, etc.) is a major modification and requires a permit, plan review, and inspection. Even owner-occupants must hire a licensed contractor for fuel-type changes. This also triggers full energy-code compliance checks and may require venting system modifications, so plan for 1–2 weeks and $150–$300 in permit fees on top of equipment and labor.

What happens if I'm caught doing unpermitted HVAC work in Hazelwood?

You'll receive a stop-work order ($250–$500 fine) and must pull a retroactive permit and pay double permit fees. Your homeowner's insurance may deny coverage for the unpermitted work, and when you sell, you must disclose it on the Missouri Residential Property Condition Disclosure Form, which can tank your sale or trigger a $10,000–$30,000 price reduction. Always pull the permit — it costs $100–$200 and protects you.

Are there any special requirements for HVAC systems in Hazelwood's karst zone (south Hazelwood)?

The Building Department may request documentation that the outdoor unit pad is properly sloped and compacted, and that condensate drainage doesn't create subsidence risk. Bury condensate lines below the 30-inch frost depth and slope them toward a proper drain system. If your property is in karst terrain, mention it to your contractor and ask if they've dealt with karst-specific code requirements before.

Do I need to upgrade my furnace or AC to meet Hazelwood's energy code?

When replacing a furnace, the new unit must meet AFUE 95% minimum. When installing a new AC or heat pump, the system must meet SEER2 13 minimum (federal standard as of 2024, enforced by Hazelwood). If your existing equipment is older and still functioning, you don't need to replace it. But if you do replace it, the new equipment must meet these minimums. Many contractors offer higher-efficiency models (AFUE 98%, SEER2 16–18) that qualify for utility rebates or federal tax credits, so compare the cost of an upgrade before deciding.

Disclaimer: This guide is based on research conducted in May 2026 using publicly available sources. Always verify current hvac permit requirements with the City of Hazelwood Building Department before starting your project.

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