Budget planning guide

Room Addition cost in Seattle, WA

A transparent starter-scope range for homeowners planning room addition in Seattle, WA. Review the assumptions, then use the project estimator for your own scope.

Starter-scope range

$11,780–$16,630

Planning midpoint: $13,860

The planning model applies a higher regional cost factor for this market.

What the model includes

Starter scope and assumptions

Adjust quantities for your project

Foundation

200 sq ft × $19.5

$3,900

Framing

200 sq ft × $15.6

$3,120

Roofing

220 sq ft × $10.4

$2,290

Electrical & Plumbing

1 lump sum × $4,550

$4,550

This is a budgeting example based on a defined starter scope, not a quote or a live survey of local bids. Actual pricing depends on measurements, site conditions, material choices, permits, contractor availability, and the final scope.

Local guides

Compare starter scopes by city

New York, NYLos Angeles, CAChicago, ILHouston, TXPhoenix, AZPhiladelphia, PASan Antonio, TXSan Diego, CA

Related project guides

Plan another part of the job

General Contractor cost guide

View planning assumptions

Home Renovation cost guide

View planning assumptions

Kitchen Remodeling cost guide

View planning assumptions

Bathroom Remodeling cost guide

View planning assumptions

Basement Finishing cost guide

View planning assumptions

Deck Building cost guide

View planning assumptions