Cost to Half Bath Addition in Seattle, WA (2026)
If you’re budgeting a half bath addition in Seattle, most projects run $6,148-$18,445, 23% above the $8,500 national average. What moves that number most is usually one thing: Proximity to Existing Plumbing. On its own it can swing the cost by $1,500 - $6,000, so that’s the decision to slow down on before you sweat the smaller stuff.
Easiest place to save: Locate the new half bath on the opposite side of a kitchen or main bathroom wall - shared plumbing walls cut rough-in costs by $1,500-$3,000
In the West Coast (where Seattle sits): CA licensed plumbers and electricians command premium rates; Hawaii can be 35-40% above average.
$6,148-$18,445 in Seattle
23% above the national average · 1.23x cost multiplier
In Seattle, a half bath addition runs $6,148 to $18,445 on average - about 23% above what homeowners pay nationwide. The West Coast market's labor costs account for most of the gap, with material pricing and local permitting fees adding to the spread. Use the cost table below to compare budget, mid-range, and premium options side by side.
Cost Breakdown in Seattle
| Line Item | Low | Mid | High |
|---|---|---|---|
| Cost per room | $3689 | $10452 | $18445 |
| Materials | $2,052 | $3,990 | $7,980 |
| Labor | $3,334 | $5,334 | $10,001 |
| Permits | $684 | $912 | $1,368 |
| Total | $6,070+24% vs. national avg | $10,578+23% vs. national avg | $20,489+23% vs. national avg |
Budget
Converting a closet or unused corner near existing plumbing. Stock toilet, pedestal sink, basic tile floor.
Mid-Range
New framed walls, proper plumbing rough-in, vanity with storage, porcelain tile, ventilation fan.
Premium
Fully built-out addition with custom vanity, designer tile, vessel sink, heated floor, designer lighting.
Material Options
Material prices below are national averages; availability in Seattle may shift costs slightly.
| Material | Cost/Unit | Best For |
|---|---|---|
| Pedestal Sink | $150-$600 installed | Small half baths under 25 sq ft, traditional or vintage aestheticsSpace-saving, classic look, lower cost, easy to install |
| Compact Vanity (24-30 inch) | $400-$1,500 installed | Most half baths - the storage is worth itStorage for toiletries and cleaning supplies, cleaner look, many styles |
| Wall-Mounted Floating Vanity | $600-$2,500 installed | Modern or contemporary home styles, tight spacesMakes small space feel larger, modern aesthetic, easy floor cleaning |
| Patterned Cement or Encaustic Tile Floor | $8-$20/sq ft materials | Making a design statement in a small powder roomHigh visual impact in a small space, unique, trending |
| Basic Elongated Toilet | $300-$700 installed | Standard half baths with adequate floor spaceComfortable, widely available, reliable |
Other Projects in Seattle
Seattle Estimate
Typical Range
$6,148-$18,445
vs. National Average
23% above national
Cost Multiplier
1.23x
Cost Per room
$3689-$18445
This 1.23x estimate prices Seattle labor from BLS Occupational Employment and Wage Statistics (May 2025) and applies a lighter regional adjustment to materials and permits, which vary less by metro than labor does. Actual bids vary by contractor, project scope, and timing.
See national average costs →