400 Mercer St, Seattle, WA 98109

Office · Seattle · Seattle-Bellevue metro, WA

One of 957 reachable office buildings in Seattle. Larger than 73% of office buildings in Seattle (median 20,410 SF), derived from assessor records.

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Building size: 80,019 SF, King County Assessor
Lot size: 14,409 SF, King County Assessor
Year built: 1987, King County Assessor
Stories: 6, King County Assessor
Predominant use: Midrise Office Building, King County Assessor
Assessed value: $15,766,000, per the King County Assessor (not a market appraisal)
Assessed value per building SF: $197.03/SF, derived from assessor records
Lot coverage: 555%, derived from assessor records
Vintage: 1980s vintage
Zoning: SM-UP 85 (M1), King County
County use code: Office Building

Nearby comparable buildings

Same building type, by distance. Assessor facts only; not an opinion of value.

517 Aloha St, Seattle · 0.2 mi · 8,300 SF · built 1926 · assessed $338.24/SF
401 5th Ave N, Seattle · 0.2 mi · 1,803 SF · built 1965
601 Valley St, Seattle · 0.2 mi · 18,288 SF · built 1969 · assessed $221.12/SF
157 Roy St, Seattle · 0.2 mi · 12,122 SF · built 1963
160 Roy St, Seattle · 0.2 mi · 11,336 SF · built 1975 · assessed $272.04/SF
701 Dexter Ave N, Seattle · 0.3 mi · 335,496 SF · built 2024 · assessed $598.54/SF

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Sale history and market context

MakeMe Estimate: $15,401,359 (estimated market value), with a likely range of $13,919,011 to $20,067,242 (half of recent verified sales in this segment landed inside that range). Based on 12 verified arm's-length comparable sales (through 2026-05-29). Not an appraisal. How this estimate works.

Last sold: 2008-10-31 for $12,043,000 (recorded arm's-length sale).

Current ownership dates to 2016 (about 10 years) per recorded transfers.

2016-09-18: transfer from Washington Property Group LLC to Gates Archive LLC (non-market transfer), rec. 20160919000425

2008-10-31: $12,043,000 from CVK LLC to Washington Property Group LLC, rec. 20081031000993

3 administrative transfers (no consideration), 1994 to 2003

Source: King County recorded sales extract; buyer and seller shown only when a company or organization. Individual names are withheld.

Value over time

Solid line: county appraised value per King County tax rolls. Shaded range: our modeled estimate for each year, built from recorded arm's-length sales in the building's segment; years without enough sales stay unmodeled. Dots: recorded arm's-length sales. Not an appraisal. How this estimate works.

Land, site, and value history

Assessed value moved from $9,384,000 (2011) to $15,766,000 (2026), up 68% over 15 years, per county tax rolls. The 2026 roll splits $15,766,000 into $7,924,900 land and $7,841,100 improvements.

Zoning: SM-UP 85 (M1) (per King County)

Lot: 14,409 sq ft

Water: Water District (per King County)

Sewer: Public (per King County)

Access: Public

Street surface: Paved

Floor and use mix: Office Building 51,592 SF; Parking Structure 14,214 SF; Storage Warehouse 14,213 SF (county building sections)

County districts report (schools, fire, sewer, council; on kingcounty.gov)

Permit history

2025-02-18: Electrical, declared value $4,000 (Screened), permit 7071038-EL

2024-08-19: Electrical, declared value $18,288 (Screened), permit 7041581-EL

2021-10-25: Remodel, declared value $30,000 (Complete), permit 6841918-CN

2018-03-06: Remodel, declared value $18,550,000 (Complete), permit 6634933

2014-04-23: Remodel, declared value $830,422 (Complete), permit 6405497

Source: King County permit records (newest first).