Seattle Mechanical Permit

When Seattle Requires a Mechanical Permit

Seattle requires a mechanical permit for most HVAC work performed within city limits. The Seattle Department of Construction & Inspections (SDCI) administers mechanical permits separately from electrical permits — a single HVAC installation often needs both.

The basic rule: if you're installing new equipment, altering an existing system, or changing the fuel source, you need a mechanical permit. Even like-for-like equipment replacements that wouldn't trigger a permit in some unincorporated Washington counties require one in Seattle.

Common Work That Triggers a Permit

Always needs a mechanical permit:

• New furnace, heat pump, or air conditioning installations
• Boiler installations or replacements
• Ductwork modifications that change system capacity or layout
• Fuel source conversions (switching from gas to electric heat pump, or vice versa)
• Commercial kitchen exhaust hood installations
• Refrigeration system installations over a certain capacity

Generally exempt:

• Portable heating or cooling appliances
• Simple thermostat replacements with no wiring changes
• Replacing filters, belts, or other maintenance components

For refrigeration work specifically, Seattle adds another layer: any refrigeration or air conditioning installation, repair, or alteration also requires an active Seattle Refrigeration Contractor License — a credential separate from the mechanical permit. You can't pull a refrigeration-related mechanical permit without showing that license.

How to Apply

Seattle processes mechanical permits through the Seattle Services Portal. The application process:

1. Create an account on the Seattle Services Portal if you don't have one
2. Submit the application with project details — equipment type, capacity, location, and scope of work
3. Pay the permit fee — fees are calculated based on project valuation and follow the SDCI fee subtitle schedule (updated annually)
4. Schedule inspections — typically a rough-in inspection during installation and a final inspection after completion

Turnaround times vary by project complexity. Simple residential equipment replacements often get same-day or next-day approval. Larger commercial projects with plan review requirements take longer.

The Double-Fee Penalty

Working without a permit in Seattle carries a specific financial penalty beyond the standard L&I fines for unregistered contracting: SDCI charges double the permit fee for work performed before the permit was obtained.

If a $200 permit was required and you started work first, you're paying $400 — and that's on top of any state-level citations L&I might issue for separate violations. SDCI inspectors do check active construction sites, and neighbors can (and do) report unpermitted mechanical work.

Electrical Permits Are Separate

A mechanical permit covers the mechanical scope — equipment mounting, ductwork, refrigerant lines, condensate drainage, gas piping. It does not cover the electrical connections.

Wiring the outdoor condenser, running low-voltage thermostat cable, or installing a disconnect switch all require a separate electrical permit. Seattle handles its own electrical inspections through SDCI, and the work must be performed by a certified 06A or 06B specialty electrician.

A single residential mini-split installation in Seattle can easily require three separate authorizations: a mechanical permit from SDCI, an electrical permit from SDCI, and a valid Seattle Refrigeration Contractor License. Missing any one of these puts you at risk for citations from the respective authority.

Inspections and Closeout

Seattle mechanical inspections follow a standard two-stage process for most residential HVAC work:

Cover inspection — Conducted while ductwork, piping, and equipment mounting are still accessible (before drywall closure or ceiling panel replacement). The inspector verifies clearances, combustion air provisions, and code-compliant routing.

Final inspection — Conducted after the system is operational. The inspector checks that the equipment is functioning, venting is properly terminated, and all safety controls are working.

Passing both inspections closes the permit. Failing an inspection means corrections and a re-inspection — each additional inspection may carry its own fee.

Navigating Seattle's Multi-Permit Requirements

The Washington HVAC License Guide maps Seattle's permitting requirements alongside the SDCI refrigeration licensing program, state L&I credentials, and county-level mechanical permit variations, so you know exactly which authorizations apply before you bid on any Seattle-area project.

See more Washington guides →