Day & Zimmermann

Day & Zimmermann is an American company dating back to 1901 that works across industrial construction, defence and workforce services. It maintains and builds power and process plants, manufactures munitions, and provides security and engineering services to government customers. Its recruiting arm operates under the Yoh name.

Services

• Maintenance and construction: work on nuclear, gas, coal, hydro, chemical, industrial and solar facilities, including life-extension projects.
• Munitions: direct and indirect fire munitions, warheads, fuzing and precision products, propellant bags and demilitarisation of conventional munitions.
• Government services: architecture and engineering, operations and maintenance, facility management and integrated security, including for US embassies.
• Recruiting and workforce solutions: staffing and recruitment process outsourcing through its Yoh business.

Clients

Corporations and governments around the world, including US military and diplomatic customers such as the Navy and Marine Corps.

Key facts

• Founded: 1901
• Recognition: listed among Engineering News-Record's 500 design firms for 2026
• Leadership: chaired by Harold L. Yoh, III