Construction and engineering firm Day & Zimmermann will significantly reduce its Center City office space as it relocates next year to 1835 Market Street. The company has signed a long-term, 48,074-square-foot lease, moving from over 100,000 square feet at 1500 Spring Garden Street, where it has been headquartered for nearly two decades.

Despite the downsizing, the deal marks one of Center City’s largest office leases of the year, according to Savills. The third-generation, family-owned company — founded in 1901 — provides construction, engineering, staffing, and defense services to global corporations and governments.

Day & Zimmermann reported $3 billion in revenue in 2024, up from $2.3 billion the prior year, ranking sixth among the Philadelphia region’s largest private companies. The firm employs more than 1,600 people locally and 37,000 worldwide.