File electrical, plumbing, and mechanical sub-permits

Three separate permits

In Seattle:

• Electrical — pulled by your licensed electrician through SDCI.
• Mechanical (HVAC) — pulled by your licensed mechanical contractor through SDCI.
• Plumbing — pulled by your licensed plumber through King County Public Health (Seattle plumbing permits run through the county, not the city).

Each is filed by the licensed sub directly. As the homeowner you're not handling the paperwork — you're confirming each sub has actually filed before they start work.

What's in scope

• Electrical: new circuits to upstairs, possible service upgrade if the existing 100A panel can't carry the new load (very common on 1920s houses with the original panel still in place).
• Mechanical: ductwork or mini-split runs to the new space, ventilation (HRV or ERV is now standard), gas line modifications if any.
• Plumbing: new bath rough-in upstairs, drain stack tie-ins, water supply runs, possible water heater swap if the existing tank can't carry the new load.

When to file

Sub-permits can be filed as soon as the building permit is in review — they don't wait for issuance. Filing in parallel saves 2–4 weeks at the back end.

Cost

Each sub-permit is $300–$800 depending on scope. Add up to roughly $1,500–$3,000 total for the three sub-permits.