Tishman Speyer Sells Mountain View Office Building to Spear Street Capital for $121.5 Million
Tishman Speyer has sold 400 Castro St., a 138,000-square-foot Class A office building in Mountain View, California, to Spear Street Capital for $121.5 million. The deal works out to approximately $876 per square foot.
Deal Details: A Fully Leased Silicon Valley Asset
The six-story building at 400 Castro St. was built in 2002 and carries a LEED Platinum certification. At the time of sale, the property was 100% leased, with law firm Fenwick & West occupying the building. The transaction represents a disposition of a stabilized, income-producing asset in one of Silicon Valley's established office submarkets.
Property records list the building's rentable area at 138,681 square feet, slightly above the 138,000-square-foot figure cited in the announcement. The Mountain View property sits in a submarket where average asking rents reached $6.57 per square foot per month in the second quarter of 2026, among the stronger rent levels in the Silicon Valley region.
Market Context: Flight to Quality in Silicon Valley Office
The sale comes against a backdrop of persistent, if gradually improving, office vacancy across Silicon Valley. The region's overall office vacancy rate stood at 16.0% in the second quarter of 2026, down from 16.7% in the first quarter and 17.7% a year earlier. Other market estimates placed vacancy somewhat higher, with figures ranging from 15.2% to 18.2% depending on the methodology and submarket scope used.
Despite that elevated vacancy environment, the 400 Castro St. transaction illustrates that fully leased, Class A assets with creditworthy tenants continue to attract institutional capital at competitive pricing. Silicon Valley average asking rents averaged $4.99 per square foot per month on a full-service gross basis in the second quarter of 2026, up 6.6% year over year from $4.68. Separate market reports placed average asking rents between $5.22 and $5.27 per square foot per month for the same period.
About the Parties
Tishman Speyer is a global real estate developer, owner, and operator. Spear Street Capital is a real estate investment firm focused on office properties in technology-driven markets.