Cost to Basement Bathroom Addition in Seattle, WA (2026)
If you’re budgeting a basement bathroom addition in Seattle, most projects run $8,443-$24,121, 21% above the $12,500 national average. What moves that number most is usually one thing: Below-Slab vs. Macerating System. On its own it can swing the cost by $2,000 - $8,000, so that’s the decision to slow down on before you sweat the smaller stuff.
Easiest place to save: Start with a half bath (toilet and sink) instead of a full bath - you get 70% of the functionality at 50% of the cost.
$8,443-$24,121 in Seattle
21% above the national average · 1.21x cost multiplier
In Seattle, a basement bathroom addition runs $8,443 to $24,121 on average - about 21% 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 bathroom | $5427 | $15076 | $30152 |
| Materials | $3,192 | $6,840 | $15,960 |
| Labor | $5,125 | $9,609 | $15,374 |
| Permits | $684 | $912 | $1,140 |
| Total | $9,001+22% vs. national avg | $17,361+21% vs. national avg | $34,184+20% vs. national avg |
Budget
Half bath (toilet and sink) added to unfinished basement near existing stack. Basic fixtures, standard tile, and minimal framing.
Mid-Range
Full 3-piece bath (toilet, sink, shower) with below-slab ejector or macerating toilet system, mid-range tile, standard vanity, and proper ventilation.
Premium
Full bath with tile shower, premium fixtures, custom vanity, below-slab plumbing with ejector pump, heated floor, and full exhaust ventilation system.
Material Options
Material prices below are national averages; availability in Seattle may shift costs slightly.
| Material | Cost/Unit | Best For |
|---|---|---|
| Macerating (Upflush) Toilet System | $700-$1,800 unit only | Budget basement bathroom additions, retrofit situationsNo concrete breaking required, lower upfront cost, relocatable |
| Below-Slab Ejector Pump System | $1,500-$4,000 for pump and pit only | Long-term reliable basement bathrooms, high-use situationsCode-compliant everywhere, gravity-fed to pump, quieter |
| Standard Ceramic Tile | $3-$10/sq ft materials only | Budget to mid-range basement bathroomsAffordable, durable, waterproof, wide selection |
| Luxury Vinyl Tile (LVT) | $3-$8/sq ft materials only | Budget installs, DIY-friendly flooringWarm underfoot, waterproof, easy DIY install |
| Porcelain Tile (Floor and Shower) | $6-$25/sq ft materials only | Premium basement bathrooms, shower surroundsMost durable, low water absorption, premium look |
Other Projects in Seattle
Seattle Estimate
Typical Range
$8,443-$24,121
vs. National Average
21% above national
Cost Multiplier
1.21x
Cost Per bathroom
$5427-$30152
This 1.21x 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 →