HVAC permits in Mercer Island: fees, timeline & requirements (2026)
Everything you need to know about pulling an HVAC / mechanical permit in Mercer Island, Washington — when one is required, what it costs, how long review takes, what documents are required, and which inspections you can expect. Cited to Mercer Island Community Planning & Development.
Free lookup, no account needed — the office that issues the permit at your address, the mapped areas on the lot, cited to Mercer Island's source.
When does HVAC work need a permit in Mercer Island?
WAC 51-52 (2021 IMC) and WAC 51-56 (2021 UPC) require mechanical permit for any equipment install, replacement, or relocation. WSEC R403 requires sizing per Manual J/S/D for new equipment.
How Mercer Island adopted this rule
The threshold comes from the state code (WAC 51.52), which Mercer Island adopts by reference in the provision quoted below.
“The 2021 Edition of the International Mechanical Code (IMC), as adopted and amended by the State Building Code Council in WAC Chapter 51-52, as published by the International Code Council, is adopted by reference with the following additions, deletions and exceptions. Provided, that Chapter 1, Part 2, Administration and Enforcement, is not adopted and the Construction Administrative Code, as set forth in chapter 17.14 MICC, shall be used in place of IMC Chapter 1, Part 2, Administration and Enforcement.”Source ↗verified 2026-04-29
Required submittals
- Equipment specs (model #, capacity)
- Manual J/S/D for new system
- Gas piping diagram if applicable
- Electrical permit cross-reference
Inspection sequence
- Rough-in / gas pressure test
- Final
Contractor specialties needed
General contractor
Who can do this work in Mercer Island?
Kolmo Construction is a licensed Washington general contractor — KOLMOL*753JS, active through April 10, 2027, bonded and insured — working throughout Mercer Island and King County. Kolmo manages the HVAC / mechanical job from start to finish: a licensed HVAC subcontractor performs the work and the permit, and Kolmo coordinates the scope, schedule, inspections and any related construction. Call (206) 410-5100 for a Mercer Island HVAC / mechanical quote.
Notes & caveats
From multi-jurisdiction tip sheet (Mercer Island column shows √ for): Furnaces, air conditioners, and heat pumps; Fireplaces, wood-burning stoves, and inserts; Gas piping; Water heater installation. Exempt: portable spas/saunas that plug in (no electrical work).
How to apply yourself
- 1. Check who issues the permit. Run an address lookup for your HVAC work in Mercer Island — we'll confirm which office issues the permit at that address and whether the lot is in a critical area or a flood hazard area, which Mercer Island's rule turns on.
- 2. Assemble submittals: the 4 documents under Required submittals above.
- 3. Submit through the city portal: Mercer Island Community Planning & Development ↗
- 4. Track review. Respond to reviewer comments promptly.
- 5. Pay issuance fees (Mercer Island's fee schedule sets them) and pick up the permit. Inspection card travels with the job.
Or have Kolmo do it
Kolmo runs the job: a licensed HVAC subcontractor does the HVAC / mechanical work and pulls the permit, and Kolmo coordinates the scope, schedule, inspections and any related construction.
Licensed WA general contractor KOLMOL*753JS · bonded & insured
HVAC permits in Mercer Island — FAQ
When does HVAC work need a permit in Mercer Island?
WAC 51-52 (2021 IMC) and WAC 51-56 (2021 UPC) require mechanical permit for any equipment install, replacement, or relocation. WSEC R403 requires sizing per Manual J/S/D for new equipment.
How much does an HVAC / mechanical permit cost in Mercer Island?
With no building permit, Mercer Island prices a mechanical permit at its $46 issuance fee plus unit fees, $214 at the least: $29 for each furnace up to 100,000 Btu/h, $29 a compressor up to 3 horsepower, $20 an air handler up to 10,000 cfm, $46 a ventilation fan, and $24 for a repair or addition to a heating or cooling system. Exchanging an existing single-family HVAC system, thermostat included, or a forced-air unit of the same type is $120. With a building permit, the mechanical inspection is part of the 31% combination fee (2026 Fee Schedule).