Mechanical Permits

A mechanical permit is required when installing or replacing piping or appliances that use natural and other fossil fuels, and when installing or replacing HVAC equipment. Some permit applications will require plan review.

Projects that require a mechanical permit include:

  • Replacing like-for-like HVAC equipment, such as a gas water heater, furnace or heat pump. All new equipment must meet current codes.
  • Extending or replacing duct work.
  • Installing a zero-clearance fireplace, fireplace insert, pellet stove and similar devices.
  • Installing a generator (fuel appliance).
  • Installing a new gas line or modifying an existing line. Examples are fireplace logs, barbecues, cook tops and gas hot water tanks.
  • Condensate piping – usually designed by a plumber, this requires a mechanical permit.

Examples of when you don't need a mechanical permit:

  • Self-contained refrigeration equipment with less than 10 pounds of refrigerant and/or less than 1 HP (and no refrigerant line welding) is exempt.
  • Auto shops that install air and fluids for serving vehicles do not fall under the building codes.

Your project may require plan review. Examples of projects that require you to submit mechanical plans with your application include:

  • New, additions, alterations and replacement to non-residential building and multifamily residential (three or more dwelling units per building) projects
  • Townhomes over three stories
  • Relocation or addition of 15 or more diffusers or grilles
  • Relocation or addition of five or more VAV boxes
  • Penetration of fire-rated construction
  • Cooking equipment, commercial kitchen hoods (Type I and II)
  • Refrigeration
  • HVAC equipment
  • Fuel gas distribution piping and equipment, fuel gas-fired appliances, fuel gas-fired appliance venting and fuel tanks
  • Boiler venting and combustion air (Boilers are permitted thru L&I; a boiler is any water heater over 199 MBH)
  • Work involving ventilation for a nail or hair salon.
  • Exterior work in a Design District
  • Rooftop installations: screening required
  • Generators

Submit permit applications and plans online at

Submittal Documents and Forms

The following documents or forms may be required to proceed with your permit application based on the scope of your project. Contact a mechanical reviewer if you believe that a required submittal does not apply to your project. 

Mechanical permits that do not require plan review can be issued the same day. These permits will still require inspections.

Things you should know:

  • Townhomes designed under the IRC do not require a plan review.
  • Walk-in coolers require a building permit.
  • Self-contained refrigeration (evaporator & condensing unit) might require a mechanical permit.
  • Site plans are required to verify intake and exhaust distances from property lines, roads, parking lots and other buildings. They are not needed if all work is inside the building.

NOTE: Many buildings in Bellevue have smoke control systems. Any mechanical work in one of these buildings will require the applicant to verify the affects to the smoke control system.

Fees and Timelines