Home addition cost in Washington
Statewide estimate from BLS wages and BEA prices. Reviewed Nov 4, 2026.
- Statewide range (300 sq ft)
- $45,200 – $91,400
- Per sq ft
- $149 – $298
- before permit
- Versus US midpoint
- +19%
- US $57,500
- Metros covered
- 7
Washington prices for home addition: $45,200 to $91,400 for 300 sq ft, or $149 to $298 per sq ft without the permit. The state midpoint is 19% above the national one. Local wages for carpenters are $35.67 an hour.
Inside Washington, the metros we cover range from $62,100 (Yakima) to $70,900 (Seattle) at the midpoint. Pick your closest city in the table for a tighter number.
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Estimated cost for 300 sq ft in Washington (statewide), standard level
$59,100 to $77,600
About $193 to $253 per sq ft before permits. Labor is about 71% of the bill.
| Part | Low | High |
|---|---|---|
| Materials | $16,300 | $21,300 |
| Labor | $41,800 | $54,600 |
| Permits and fees | $1,000 | $1,650 |
| Total | $59,100 | $77,600 |
Cost breakdown for 300 sq ft in Washington
| Part of the job | Low | Midpoint | High | Share |
|---|---|---|---|---|
| Materials | $12,500 | $18,800 | $25,000 | 28% |
| Labor | $32,100 | $48,200 | $64,200 | 71% |
| Permits and fees | $540 | $1,350 | $2,150 | 2% |
| Total | $45,200 | $68,300 | $91,400 | 100% |
Home addition cost by metro in Washington
2 of the 7 metros sit above the statewide midpoint of $68,300, and the top-to-bottom gap is 14%. Each row prices the default size with that metro's own BLS wages and BEA price levels, so the gap between rows is real local variation rather than a flat markup.
| Metro | Range (300 sq ft) | Midpoint | vs. state |
|---|---|---|---|
| Seattle, WA | $46,900 – $94,800 | $70,900 | +4% |
| Bellingham, WA | $45,500 – $92,000 | $68,800 | +1% |
| Kennewick, WA | $43,500 – $88,100 | $65,800 | −4% |
| Olympia, WA | $42,800 – $86,500 | $64,700 | −5% |
| Bremerton, WA | $42,400 – $85,800 | $64,100 | −6% |
| Spokane, WA | $41,500 – $84,000 | $62,700 | −8% |
| Yakima, WA | $41,100 – $83,200 | $62,100 | −9% |
What carpenters and the other trades earn in Washington
Washington's labor line is priced from 6 trades, each compared with its US median wage. After weighting by each trade's share of the work, the state comes out at 1.26 times the national level.
Carpenters (47-2031), 50% of the weighting: a median of $35.67 an hour, 22% above the US median of $29.12. The middle half of them earn between $29.15 and $44.55 an hour. About 26,960 work in the state. That is 75.9 per 10,000 jobs, compared with 43.1 nationally, which suggests plenty of local crews to bid.
Cement masons and concrete finishers (47-2051), 10% of the weighting: a median of $37.27 an hour, 36% above the US median of $27.41. The middle half of them earn between $28.31 and $47.25 an hour. About 4,440 work in the state. That is 12.5 per 10,000 jobs, compared with 13.3 nationally, so the supply of crews looks typical.
For electricians (47-2111, weighted 10%) the local median is $45.78 an hour, which is 51% above the national $30.38. The middle half of them earn between $32.04 and $58.43 an hour. BLS counts 19,380 of them working in the state, 54.6 for every 10,000 jobs (US: 48.7), so the local bench is about average.
Plumbers, pipefitters and steamfitters (47-2152), 10% of the weighting: a median of $38.96 an hour, 27% above the US median of $30.67. The middle half of them earn between $28.86 and $51.64 an hour. About 12,470 work in the state. That is 35.1 per 10,000 jobs, compared with 30.0 nationally, which suggests plenty of local crews to bid.
For drywall and ceiling tile installers (47-2081, weighted 10%) the local median is $35.16 an hour, which is 24% above the national $28.33. The middle half of them earn between $30.15 and $48.45 an hour. BLS counts 2,670 of them working in the state, 7.5 for every 10,000 jobs (US: 5.3), so the local bench is deeper than average.
Roofers (47-2181), 10% of the weighting: a median of $29.16 an hour, 9% above the US median of $26.65. The middle half of them earn between $25.15 and $38.21 an hour. About 5,890 work in the state. That is 16.6 per 10,000 jobs, compared with 8.7 nationally, which suggests plenty of local crews to bid.
A crew paid at the 75th percentile for carpenters ($44.55 an hour) would add about $5,850 to the statewide midpoint; one at the 25th percentile ($29.15) would take off about $4,300. Use that as a rough guide to how far a bid can sit from our midpoint on wages alone.
BLS counts 3,550,970 jobs across Washington (May 2025), which is 2.3% of US employment.
| Trade | Weight | 25th pct | Median | 75th pct | US median | Ratio | Level used |
|---|---|---|---|---|---|---|---|
| Carpenters (47-2031) | 50% | $29.15 | $35.67 | $44.55 | $29.12 | 1.22 | state |
| Cement masons and concrete finishers (47-2051) | 10% | $28.31 | $37.27 | $47.25 | $27.41 | 1.36 | state |
| Electricians (47-2111) | 10% | $32.04 | $45.78 | $58.43 | $30.38 | 1.51 | state |
| Plumbers, pipefitters and steamfitters (47-2152) | 10% | $28.86 | $38.96 | $51.64 | $30.67 | 1.27 | state |
| Drywall and ceiling tile installers (47-2081) | 10% | $30.15 | $35.16 | $48.45 | $28.33 | 1.24 | state |
| Roofers (47-2181) | 10% | $25.15 | $29.16 | $38.21 | $26.65 | 1.09 | state |
| Blended | 100% | 1.26 | |||||
Washington seasons and home addition
Weather decides when digging and ground work can happen, and Washington is not uniform. The table uses NOAA's 1991-2020 climate normals from the weather station nearest each metro we cover, and counts the months that are neither cold nor hot enough to complicate the job.
Seattle has the longest comfortable season of the metros we cover in Washington at 12 months; Yakima has the shortest at 6 (April through June and August through October). Rainfall runs from 8 inches a year in Kennewick to 57 inches in Bremerton.
We do not adjust prices by month, because we have no reliable published data on seasonal pricing. Timing is still worth raising when you collect bids.
| Metro | Jan avg low °F | Jul avg high °F | Precip (in/yr) | Comfortable months |
|---|---|---|---|---|
| Seattle | 37 | 77 | 38 | 12: all year |
| Spokane | 26 | 87 | 17 | 7: April through October |
| Olympia | 33 | 78 | 51 | 11: March through January |
| Kennewick | 28 | 93 | 8 | 6: March through June and September through October |
| Yakima | 24 | 90 | 8 | 6: April through June and August through October |
| Bremerton | 36 | 77 | 57 | 12: all year |
| Bellingham | 34 | 73 | 35 | 12: all year |
Basic, standard or premium: Washington prices
Bands overlap on purpose, since a good standard job can cost as much as a light premium one. Below are the three bands for the default size, then a grid from bump-out (100 sq ft) to large suite (600 sq ft).
Basic
$45,200 to $63,700
Bump-out or simple room without plumbing
Standard
$59,100 to $77,600
Standard room addition with HVAC and electrical
Premium
$72,900 to $91,400
Large addition with bath or kitchen and a new foundation
| Size | Basic | Standard | Premium |
|---|---|---|---|
| bump-out (100 sq ft) | $15,400 – $22,000 | $20,400 – $27,000 | $25,300 – $31,900 |
| 20x20 room (400 sq ft) | $60,100 – $84,500 | $78,400 – $103,000 | $96,700 – $121,000 |
| large suite (600 sq ft) | $89,800 – $126,000 | $117,000 – $153,500 | $144,500 – $180,500 |
Why two Washington quotes can differ
Type of addition
A new room is $125-$250 per sq ft; a bump-out $85-$200; an attic conversion $50-$150; a garage conversion $50-$200 (HomeGuide).
Plumbing and fixtures
Adding a bathroom or kitchen drives the price up the most.
Permits
Construction permits run $500-$2,000, or $5-$21 per $1,000 of project cost (HomeGuide).
Foundation
A foundation, framing, roofing and matching exterior finishes all have to be built before the interior work starts.
Washington against its neighbors
Washington ranks 4 of 51 (the 50 states plus DC) for home addition, where 1 is the most expensive. The costliest is Hawaii at $76,300 and the cheapest Arkansas at $48,200, both for 300 sq ft at the midpoint. Washington sits at $68,300. The five states closest by workforce center are listed below.
| State | Distance | Range | Midpoint | vs. here |
|---|---|---|---|---|
| Oregon | 170 miles away | $43,300 – $87,700 | $65,500 | −4% |
| Idaho | 380 miles away | $34,700 – $70,300 | $52,500 | −23% |
| Montana | 500 miles away | $38,700 – $78,400 | $58,600 | −14% |
| Utah | 650 miles away | $35,000 – $71,100 | $53,000 | −22% |
| Nevada | 780 miles away | $38,000 – $76,900 | $57,400 | −16% |
Other Washington jobs that often go with home addition
Each project weights the trades differently, so Washington's wage level does not push every price by the same amount. Compared with the US midpoint, bathroom remodel is +18% and roof replacement +9%.
| Project | Size | Range | vs. US |
|---|---|---|---|
| Kitchen remodel | 120 sq ft | $20,200 – $34,500 | +9% |
| Bathroom remodel | 45 sq ft | $5,550 – $27,600 | +18% |
| Detached garage | 576 sq ft | $33,300 – $66,900 | +15% |
| Roof replacement | 2,000 sq ft of roof | $6,700 – $13,500 | +9% |
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Home addition in Washington: your questions
+How much does it cost to build a home addition in Washington?
$45,200 to $91,400 for 300 sq ft, using statewide wages and prices. Metro areas inside Washington can sit above or below that.
+Which city in Washington is cheapest for home addition?
Yakima at about $62,100 (midpoint, 300 sq ft). The priciest is Seattle at $70,900.
+Is home addition cheaper in Washington than the US average?
It is 19% more expensive: $68,300 against $57,500 for 300 sq ft at the midpoint.
+What share of the price is labor in Washington?
About 71% ($48,200). Materials are 28%. Statewide labor for this job is weighted 1.26x the national wage level.
+What do carpenters earn in Washington?
The BLS statewide median is $35.67 an hour, against $29.12 for the US. The 25th to 75th percentile range is $29.15 to $44.55.
+Where does Washington rank for home addition costs?
4th most expensive of 51 (the 50 states plus DC) at the midpoint, $68,300 for 300 sq ft. Rank 1 is the costliest.
+What do basic and premium home addition work cost in Washington?
For 300 sq ft, basic work runs $45,200 to $63,700 and premium work $72,900 to $91,400. Basic means: bump-out or simple room without plumbing. Premium means: large addition with bath or kitchen and a new foundation.
+Does the season matter for home addition in Washington?
Yes where winters or summers are hard. Of the Washington metros we cover, Seattle has the most comfortable months (12 of 12) based on NOAA 1991-2020 normals. Our prices do not change by month, so ask contractors whether they charge more or less in busy and slow seasons.
Home addition by city in Washington
Where these numbers come from
Base prices are national ranges from the sources below. We scale labor by local BLS wages, materials by BEA goods prices and permits by the BEA all-items price level. Full method on the methodology page.
- HomeGuide: How Much Does a Home Addition Cost? (2026) (accessed November 4, 2026)
- Cost to Renovate: Renovation Labor Report 2026: Where the Money Goes (accessed November 4, 2026)
- HomeGuide: 2026 Building Permit Costs | Fees & Cost Calculator (accessed November 4, 2026)
- BLS Occupational Employment and Wage Statistics, May 2025
- BEA Regional Price Parities, 2024
- NOAA NCEI U.S. Climate Normals, 1991-2020
Note on derived figures: Materials = 32% of the installed price, from Cost to Renovate's mid-range 'Structural' category split (56% labor, 32% materials, 11% permits and design). It is a category average rather than an addition-specific figure.