MEP rough-in + knob-and-tube remediation

What "rough" means

The mechanical, electrical, and plumbing systems go inside walls and ceilings, but not finished or trimmed out. Everything you can't see once drywall goes up.

The knob-and-tube reality

Most Seattle bungalows still have some original knob-and-tube wiring. Washington's WAC 296-46B-394 restricts how K&T can be concealed — covering live K&T with insulation is prohibited unless a licensed electrical contractor surveys the wiring, certifies its condition in writing, and the project meets the WAC's other conditions (overcurrent protection per NEC, no foam insulation). A second-story addition typically requires:

• Rewiring at minimum the walls and ceilings being touched by the addition.
• Often, whole-house rewire — once you're rewiring the second floor and adding a service upgrade, the marginal cost to rewire the rest of the existing house is small relative to the cumulative benefit.

Realistic numbers:

• New circuits to upstairs only (K&T elsewhere left intact and inspected): $8,000–$15,000 added to electrical scope.
• Whole-house rewire alongside the addition: $15,000–$30,000 added.

Service upgrade

Most pre-1960 Seattle houses still have a 100-amp panel (some original 60-amp panels still exist). A second-story addition with new HVAC, an EV charger consideration, and an HRV/ERV pushes most projects to a 200-amp service upgrade — typically $3,500–$8,000 including SCL coordination. Filed under the electrical sub-permit (step 3.2).

Plumbing on an old house

• Galvanized water lines (common pre-1970) often get replaced with PEX during the MEP rough — once the walls are open, the marginal cost is small.
• Cast iron drains can usually stay if they pass camera inspection. Replacement is $5,000–$15,000 if needed.
• Water heater typically gets replaced; current Seattle code pushes to heat-pump water heater for new installs.

HVAC patterns

• Heat-pump central system or mini-splits for the new + existing space.
• HRV or ERV ventilation, required by current Seattle Energy Code on substantially altered or added envelope.

Inspections

Each trade gets its own rough inspection: electrical (SDCI), mechanical (SDCI), plumbing (King County Public Health). All three have to pass before insulation.