Home addition cost in Seattle, WA
Local estimate from BLS wage data and BEA price levels. Reviewed Nov 4, 2026.
- Typical range (300 sq ft)
- $46,900 – $94,800
- Per sq ft
- $154 – $309
- before permit
- Versus US midpoint
- +23%
- US $57,500
- Rank of 300 metros
- #6
- 1 = most expensive
If you want to build a home addition in Seattle, plan on $46,900 to $94,800 for 300 sq ft, all in. Per sq ft, that is $154 to $309 for materials and labor, with the permit on top. The local midpoint runs 23% higher than the national one. Carpenters earn a median of $36.74 an hour in the Seattle area, 26% above the US median of $29.12.
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Estimated cost for 300 sq ft in Seattle, WA, standard level
$61,300 to $80,500
About $201 to $262 per sq ft before permits. Labor is about 72% of the bill.
| Part | Low | High |
|---|---|---|
| Materials | $16,200 | $21,200 |
| Labor | $44,000 | $57,500 |
| Permits and fees | $1,050 | $1,700 |
| Total | $61,300 | $80,500 |
Cost breakdown for 300 sq ft in Seattle, WA
| Part of the job | Low | Midpoint | High | Share |
|---|---|---|---|---|
| Materials | $12,500 | $18,700 | $25,000 | 26% |
| Labor | $33,800 | $50,800 | $67,700 | 72% |
| Permits and fees | $560 | $1,400 | $2,200 | 2% |
| Total | $46,900 | $70,900 | $94,800 | 100% |
Why Seattle prices look the way they do
Labor is 72% of the midpoint bill here, against 67% nationally. The mix of trades behind this job is carpenters (50%), cement masons and concrete finishers (10%), electricians (10%), plumbers, pipefitters and steamfitters (10%), drywall and ceiling tile installers (10%), roofers (10%). We weight each trade's local median wage by that share and compare it with the national median. In Seattle the blended ratio comes out at 1.33.
On the materials line, the BEA goods price index for the Seattle metro is 104.0 (US = 100). The midpoint materials bill for 300 sq ft comes to $18,700, compared with $18,000 at national prices. Permit and inspection fees are scaled by the broader index (111.1) and land at $560 to $2,200.
Climate in Seattle: timing your home addition job
We use NOAA's 1991-2020 climate normals for Seattle Sand Pt Wsfo (5 miles from the city center). These are 30-year monthly averages, not forecasts.
Weather is not a serious constraint for digging, grading and setting material in the ground in Seattle: no month in the averages is cold enough (an average overnight low at or below freezing (32°F)) or hot enough (an average daytime high of 90°F or more) to rule it out, so the workable window is all year.
Seattle gets about 38 inches of precipitation in a normal year, including roughly 4 inches of snow. The wettest months are January, November and December (5.8 inches in November). The station averages about 2 days a year at 90°F or above.
Does the season change the price? Probably, but we do not have a sourced seasonal price curve, so the estimator shows a year-round figure and does not adjust by month. When you collect quotes, ask whether scheduling in a slower month gets a better rate.
| Month | Avg high °F | Avg low °F | Precip (in) | For this job |
|---|---|---|---|---|
| Jan | 47 | 37 | 5.1 | Workable |
| Feb | 50 | 37 | 3.5 | Workable |
| Mar | 54 | 39 | 3.9 | Workable |
| Apr | 59 | 43 | 3.0 | Workable |
| May | 65 | 48 | 2.2 | Workable |
| Jun | 70 | 53 | 1.6 | Workable |
| Jul | 77 | 57 | 0.8 | Workable |
| Aug | 77 | 57 | 1.0 | Workable |
| Sep | 71 | 53 | 1.7 | Workable |
| Oct | 61 | 47 | 3.6 | Workable |
| Nov | 52 | 41 | 5.8 | Workable |
| Dec | 47 | 37 | 5.5 | Workable |
Seattle: what basic, standard and premium work costs
Three bands are cut from the same cited range and localized for Seattle wages and prices. They overlap on purpose: a good standard job and a modest premium job can cost the same. The grid below prices the same bands at 3 common sizes.
Basic
$46,900 to $66,100
Bump-out or simple room without plumbing
Standard
$61,300 to $80,500
Standard room addition with HVAC and electrical
Premium
$75,700 to $94,800
Large addition with bath or kitchen and a new foundation
| Size | Basic | Standard | Premium |
|---|---|---|---|
| bump-out (100 sq ft) | $16,000 – $22,800 | $21,100 – $28,000 | $26,300 – $33,100 |
| 20x20 room (400 sq ft) | $62,300 – $87,700 | $81,300 – $106,500 | $100,500 – $125,500 |
| large suite (600 sq ft) | $93,200 – $131,000 | $121,500 – $159,000 | $150,000 – $187,500 |
How Seattle compares
Contractors rarely work more than an hour or two from home, so the neighboring metros set a rough ceiling and floor for your quotes. Midpoints for 300 sq ft range from $62,100 to $70,900 across Seattle and its five closest metros.
| Area | Range | Midpoint | vs. here |
|---|---|---|---|
| Seattle, WAthis page | $46,900 – $94,800 | $70,900 | |
| Bremerton, WA40 miles | $42,400 – $85,800 | $64,100 | −10% |
| Olympia, WA60 miles | $42,800 – $86,500 | $64,700 | −9% |
| Yakima, WA90 miles | $41,100 – $83,200 | $62,100 | −12% |
| Bellingham, WA95 miles | $45,500 – $92,000 | $68,800 | −3% |
| Portland, OR135 miles | $46,600 – $94,300 | $70,500 | −1% |
| Washington (statewide) | $45,200 – $91,400 | $68,300 | −4% |
| United States | $38,000 – $77,000 | $57,500 | −19% |
Across 300 US metros, Seattle comes in at #6 from the top. The priciest is Honolulu, HI at $79,600; the cheapest is Brownsville, TX at $44,300 (midpoints, 300 sq ft). Statewide, Seattle is 4% above the Washington figure.
Other Washington metros
| Metro | Size | Range | Midpoint | vs. here |
|---|---|---|---|---|
| Spokane, WA | 255,820 jobs | $41,500 – $84,000 | $62,700 | −11% |
| Olympia, WA | 130,300 jobs | $42,800 – $86,500 | $64,700 | −9% |
| Kennewick, WA | 129,490 jobs | $43,500 – $88,100 | $65,800 | −7% |
| Yakima, WA | 97,010 jobs | $41,100 – $83,200 | $62,100 | −12% |
| Bremerton, WA | 93,740 jobs | $42,400 – $85,800 | $64,100 | −10% |
| Bellingham, WA | 91,390 jobs | $45,500 – $92,000 | $68,800 | −3% |
Cities with a workforce like Seattle's
Big cities and small ones price differently, so here is Seattle against the 4 metros with the closest total employment.
| Metro | Size | Range | Midpoint | vs. here |
|---|---|---|---|---|
| San Francisco, CA | 2,373,920 jobs | $49,600 – $100,500 | $75,000 | +6% |
| Minneapolis, MN | 1,951,650 jobs | $45,300 – $91,700 | $68,500 | −3% |
| Phoenix, AZ | 2,375,760 jobs | $36,700 – $74,500 | $55,600 | −21% |
| Detroit, MI | 1,904,530 jobs | $41,300 – $83,600 | $62,400 | −12% |
Seattle labor market for home addition
Wages are the part of this estimate that changes most from town to town. 6 trades carry the job here, and each is compared with its US median. The weighted result for Seattle is 1.33 times the national level.
For carpenters (47-2031, weighted 50%) the local median is $36.74 an hour, which is 26% above the national $29.12. The middle half of them earn between $30.64 and $47.93 an hour. BLS counts 14,970 of them working in the area, 71.8 for every 10,000 jobs (US: 43.1), so the local bench is deeper than average.
For cement masons and concrete finishers (47-2051, weighted 10%) the local median is $38.88 an hour, which is 42% above the national $27.41. The middle half of them earn between $29.14 and $52.52 an hour. BLS counts 2,140 of them working in the area, 10.3 for every 10,000 jobs (US: 13.3), so the local bench is thinner than average.
Electricians (47-2111), 10% of the weighting: a median of $48.93 an hour, 61% above the US median of $30.38. The middle half of them earn between $36.35 and $60.55 an hour. About 9,750 work in the metro. That is 46.7 per 10,000 jobs, compared with 48.7 nationally, so the supply of crews looks typical.
For plumbers, pipefitters and steamfitters (47-2152, weighted 10%) the local median is $45.78 an hour, which is 49% above the national $30.67. The middle half of them earn between $29.83 and $60.93 an hour. BLS counts 6,350 of them working in the area, 30.4 for every 10,000 jobs (US: 30.0), so the local bench is about average.
Drywall and ceiling tile installers (47-2081), 10% of the weighting: a median of $36.33 an hour, 28% above the US median of $28.33. The middle half of them earn between $30.94 and $49.23 an hour. About 1,840 work in the metro. That is 8.8 per 10,000 jobs, compared with 5.3 nationally, which suggests plenty of local crews to bid.
For roofers (47-2181, weighted 10%) the local median is $30.81 an hour, which is 16% above the national $26.65. The middle half of them earn between $27.23 and $44.40 an hour. BLS counts 2,970 of them working in the area, 14.2 for every 10,000 jobs (US: 8.7), so the local bench is deeper than average.
Quotes come from real crews, not medians. If the carpenters on your job are paid at the 75th percentile ($47.93 an hour) instead of the median, the labor line grows by about $7,350. At the 25th percentile ($30.64) it shrinks by about $4,000. The total moves by 10.4% or 5.7%, so wages alone rarely explain a quote that is far outside our range.
For context on the local economy, BLS counts 2,086,210 jobs in the Seattle-Tacoma-Bellevue area. That makes it the 13th largest of the 300 metros we cover, with 1.34% of US employment.
| Trade | Weight | 25th pct | Median | 75th pct | US median | Ratio | Level used |
|---|---|---|---|---|---|---|---|
| Carpenters (47-2031) | 50% | $30.64 | $36.74 | $47.93 | $29.12 | 1.26 | metro |
| Cement masons and concrete finishers (47-2051) | 10% | $29.14 | $38.88 | $52.52 | $27.41 | 1.42 | metro |
| Electricians (47-2111) | 10% | $36.35 | $48.93 | $60.55 | $30.38 | 1.61 | metro |
| Plumbers, pipefitters and steamfitters (47-2152) | 10% | $29.83 | $45.78 | $60.93 | $30.67 | 1.49 | metro |
| Drywall and ceiling tile installers (47-2081) | 10% | $30.94 | $36.33 | $49.23 | $28.33 | 1.28 | metro |
| Roofers (47-2181) | 10% | $27.23 | $30.81 | $44.40 | $26.65 | 1.16 | metro |
| Blended | 100% | 1.33 | |||||
Home addition: what moves the price in Seattle
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).
Planning more than one job in Seattle?
Because every project leans on different trades, Seattle's wage level does not move all prices equally. Against the US midpoint, bathroom remodel runs +23% and kitchen remodel +11%.
| Project | Size | Range | vs. US |
|---|---|---|---|
| Kitchen remodel | 120 sq ft | $20,500 – $34,900 | +11% |
| Bathroom remodel | 45 sq ft | $5,750 – $28,600 | +23% |
| Detached garage | 576 sq ft | $34,000 – $68,200 | +17% |
| Roof replacement | 2,000 sq ft of roof | $6,950 – $14,000 | +12% |
Get 3 local quotes
Tell us about the job and we will try to connect you with up to three local contractors for written quotes. It is free and you are under no obligation to hire. Your estimate of $61,300 to $80,500 for Seattle, WA is attached.
A detailed PDF report of this estimate, $9
The report lays out the home addition numbers for Seattle, WA line by line, with the local wage and price inputs, permit and timing notes, a quote comparison sheet and the full method. Save your estimate above, preview page 1 free, and unlock the full report for $9 one-time, or get every report with CostLocal Pro.
Home addition in Seattle: your questions
+How much does it cost to build a home addition in Seattle?
For 300 sq ft, expect $46,900 to $94,800 in the Seattle area. A standard-spec job lands at $61,300 to $80,500. Small jobs usually cost more per sq ft and large ones less.
+What is the price per sq ft for home addition in Seattle?
About $154 to $309 per sq ft for materials and labor, plus $560 to $2,200 for the permit if one is needed. The US range is $125 to $250.
+Is home addition cheaper in Seattle or Bremerton?
Bremerton is 40 miles away. The midpoint for 300 sq ft there is $64,100, which is 10% less than Seattle ($70,900). Wage and materials indexes both feed that gap.
+How much of the bill is labor in Seattle?
About 72% at the midpoint, or $50,800 out of $70,900. Materials are 26% and permits 2%. Nationally, labor is 67%.
+What would 20x20 room (400 sq ft) cost in Seattle?
$62,300 to $125,500. Pick a different size in the estimator above to get your own number.
+Does home addition need a permit in Seattle?
Often, but rules are set by your city or county building office, so call before you hire. Budget $560 to $2,200 for fees in the Seattle area (our national range of $500 to $2,000 scaled by the local price level).
+Is Seattle expensive for home addition compared with the rest of Washington?
Seattle is 4% above the Washington statewide estimate ($68,300 at the midpoint). We cover 7 metros in Washington; see the state page to compare them.
+What do carpenters earn in Seattle?
The BLS median is $36.74 an hour in the Seattle area, compared with $29.12 nationally. The 25th to 75th percentile range is $30.64 to $47.93.
+What do basic and premium home addition work cost in Seattle?
For 300 sq ft, basic work runs $46,900 to $66,100 and premium work $75,700 to $94,800. Basic means: bump-out or simple room without plumbing. Premium means: large addition with bath or kitchen and a new foundation.
+Is there a bad season to build a home addition in Seattle?
Not from a temperature point of view. NOAA's 1991-2020 normals show no month with a freezing-level overnight low or a 90°F-plus average high, so timing is mostly about contractor availability and rain.
Home addition near Seattle
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.