What Day & Zimmermann does

Day & Zimmermann is a 125-year-old, third-generation family-owned industrial services and defense contractor headquartered in Philadelphia, Pennsylvania, founded in 1901 by the Yoh family, which retains control through Chair and CEO Harold L. Yoh, III. The company operates four principal divisions: Maintenance and Construction (maintenance, engineering, and construction services for nuclear, fossil, hydro, and solar power plants as well as chemical and industrial facilities, including ASME Section III-certified nuclear-code work); Munitions (manufacturing of 155mm and 120mm artillery projectiles, 60mm and 81mm mortars, M67 hand grenades, M82A1 percussion primers, warheads, and propellant/ignitor bags across a five-state network of Government-Owned Contractor-Operated (GOCO) and commercial plants); Government Services (architecture/engineering via Mason & Hanger, integrated security and logistics via SOC, and national intelligence support for federal agencies including the Department of Energy, DoD, and federal law enforcement); and Workforce Solutions (staffing and recruitment process outsourcing via wholly-owned subsidiary Yoh, which operates in the U.S., U.K., and Germany following the Maxsys Solutions and GECO Deutschland acquisitions).

The business model is services- and contract-driven: revenue is generated through long-term negotiated alliance agreements with regulated utilities (Arizona Public Service at Palo Verde, Entergy across seven nuclear states, TVA at Sequoyah), competitive bidding on U.S. government procurement contracts (including a $2.3 billion firm-fixed-price Hawthorne Army Depot contract through December 2046 and a $30.9 million M82A1 percussion primer contract awarded August 2025), and specialized product sales of munitions to the U.S. Army and approved foreign militaries. Pricing is not publicly disclosed. Underlying capabilities rest on a heavily regulated barrier layer — ASME 'NA' and 'NPT' nuclear certifications earned in January 2026, continuous GOCO partnership at the Iowa Army Ammunition Plant since 1998, and a multi-decade DOE relationship dating to 1947 — alongside a craft workforce developed through the Nuclear Worker Training Program (73% retention rate), Registered Apprenticeship Programs across nine trades in three states, and mobile training infrastructure such as COBRA Trailers and Dynamic Learning Centers.

The go-to-market is enterprise field sales targeting federal agencies and large utility customers; marketing leans on industry recognition (ENR Top 500 Design Firms, Defense News Top 100, Forbes Largest Private Companies) and executive thought leadership rather than consumer or digital channels. The company reported approximately $3 billion in revenue and ~37,000 employees as of April 2026, with operations spanning more than 900 work locations across the United States and select international markets via the Yoh subsidiary.

Name

Day & Zimmermann

Legal name

Day & Zimmermann

Website

https://dayzim.com

Company type

Private

Founded year

1901

Operating status

Operating

Headcount range

5,001–10,000 employees

Short description

Day & Zimmermann is a 125-year-old, family-owned industrial services and defense contractor operating Maintenance & Construction, Munitions, Government Services, and Workforce Solutions divisions that serve U.S. federal agencies, regulated utilities, and industrial firms through long-term contracts and government procurement.

Ownership category

akta.pro rank

Product category

Industrial Maintenance, Engineering and Construction Services

NAICS

Management, Scientific, and Technical Consulting Services (5416), Security Guards and Patrol Services (561612)

SIC

Ordnance & Accessories, (No Vehicles/Guided Missiles) (3480)

akta.pro primary industry

Balance-of-Plant (BOP) & Civil Works for Power Plants (EUAEAAAL)

akta.pro secondary industries

Special Operations & Counterterrorism (BPAIAHAH), Security, Safety & Fire/Life Safety Management (BPABAAAE), Renewable Energy Asset O&M (Wind, Solar, Hydro, Geothermal) (EUAEAGAB)

Keywords

• Industrial maintenance services
• Munitions manufacturing
• Nuclear plant maintenance
• Government security services
• Workforce staffing solutions

Headquarters

HQ city

Philadelphia

HQ country

United States

HQ region

North America

Offices7 records

Markets served

GTM type

B2B

Offering type

Services

Cost components

Personnel, Operations, Supply Chain, Technology or R&D, Infrastructure

Revenue model

1. Maintenance and Construction Services: Provides maintenance, repair, construction, and engineering services to power plants (nuclear, fossil, hydro, solar), chemical facilities, and industrial plants. Revenue generated through long-term contracts and project-based work with utilities and industrial companies.
2. Munitions Manufacturing: Manufactures and supplies ammunition products including artillery projectiles, mortars, grenades, primers, propellant bags, and warheads to the U.S. Army and approved foreign countries. Includes demilitarization of conventional munitions.
3. Government Services: Provides integrated security, architecture/engineering, operations and maintenance, national intelligence support, and logistics services to U.S. Government and commercial clients including the Department of Defense, Department of Energy, and federal law enforcement agencies.
4. Workforce Solutions (Yoh): Provides talent and outsourcing services including staffing, recruitment process outsourcing (RPO), managed services, vendor management systems, and payroll services across aerospace/defense, engineering, IT, healthcare, and other sectors.

Go-to-market motion2 records

Distribution channels4 records

Marketing channels4 records

Core offering

Day & Zimmermann is a family-owned services company operating four divisions: Maintenance and Construction (EPC and maintenance for nuclear, fossil, hydro, solar, chemical, industrial, data center, advanced manufacturing and battery energy facilities), Munitions (manufacture of artillery projectiles, mortars, grenades, propellant bags, primers, warheads, fuzing and demilitarization services for the U.S. Army), Government Services (architecture/engineering through Mason & Hanger, integrated security and operations/maintenance through SOC, and national intelligence support), and Workforce Solutions (staffing and recruitment process outsourcing through Yoh).

Product overview

Day & Zimmermann is a family-owned services company operating across four core divisions: Maintenance and Construction (offering nuclear, fossil, chemical, industrial, solar, data center, advanced manufacturing, and battery storage services), Munitions (manufacturing and demilitarizing ammunition including artillery, mortars, warheads, and propellant systems), Government Services (architecture/engineering through Mason & Hanger, security through SOC, and intelligence support), and Workforce Solutions (staffing through Yoh.com). The company operates multiple facilities nationwide including Parsons, Kansas; Texarkana, Texas; Yankton, South Dakota; and Milan, Tennessee, serving both commercial and government customers.

Differentiator

Problem solved

Functional benefit

Products and services

• Maintenance and Construction Services Provides maintenance, construction, engineering and technical services to power, chemical and industrial plant owners to lower total cost of ownership. Covers nuclear, fossil, hydro, solar, data center, advanced manufacturing and battery energy systems for utility, industrial and government clients.
• Munitions Manufacturing Manufactures, stores and demilitarizes ammunition products including direct and indirect fire munitions, warheads, close combat munitions, propellant bags, fuzing and area denial systems for the U.S. Army and approved foreign countries. Operated through American Ordnance GOCO facilities and Day & Zimmermann Kansas/Lone Star/Yankton plants.
• Government Services Integrated provider of architecture/engineering (Mason & Hanger), facility operations and maintenance, explosive ordnance storage and disposal, international logistics, integrated security (installation, mobile, technical, working dog), and national intelligence support to U.S. Government and commercial clients including the Department of Defense, Department of Energy and federal law enforcement agencies.
• Workforce Solutions (Yoh) Talent and outsourcing services including staffing, recruitment process outsourcing (RPO), managed services, vendor management systems and payroll services delivered through Yoh.com across aerospace/defense, engineering, IT, healthcare and other professional sectors.
• Nuclear Services Maintenance, modifications, projects and construction, welding, scaffolding, and radiological protection services for nuclear power facilities. Includes nuclear-code qualified fabrication for traditional and advanced reactor projects under ASME Section III.
• Fossil and Hydroelectric Services Gas projects and construction, coal projects and life extensions, and hydroelectric maintenance and life extension services for fossil and renewable power generation facilities. Includes tainter gate maintenance, turbine repair, penstock piping and generator repairs.
• Mason & Hanger Architecture and Engineering Architecture, engineering, energy sustainability, commissioning and construction contract administration services delivered as a wholly-owned subsidiary for federal government and private-sector clients.
• SOC Security and Operations Facility management and operations, explosive ordnance storage and disposal, international logistics, installation security, mobile security, technical security, and working dog solutions for government clients.
• American Ordnance GOCO Operations Operates Government-Owned Contractor-Operated munitions facilities including Iowa Army Ammunition Plant (continuous GOCO partner since 1998) and Milan, Tennessee, producing artillery, mortars, grenades and Mine Clearing Line Charge (MICLIC) systems.

Quantifiable outcome

• 73% retention rate for Nuclear Worker Training Program participants returning for second outage
• +4 more outcomes

Named customers6 records

Segments5 records

Ideal customer profiles4 records

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature6 records

Partnerships

Four partnerships are on record, tiered core.

• Deep FissioncoreStrategic or Co-development Partner · 12 June 2026Deep Fission partnered with Day & Zimmermann to support construction of its underground Gravity reactor. Deep Fission's Gravity reactor design generates 15 megawatts per unit using conventional pressurized water technology placed in boreholes 1.6 kilometres deep.
• Deep FissioncoreStrategic or Co-development Partner · 2 June 2026Day & Zimmermann partnered with Deep Fission to construct the Gravity Nuclear Reactor, a proprietary underground small modular pressurized water reactor, at Great Plains Industrial Park in Parsons, Kansas. D&Z oversees pre-construction planning and above-ground construction while Deep Fission provides advanced reactor technology. Project part of U.S. Department of Energy's Reactor Pilot Program.
• Empire Products, Inc.coreOthers · 2 August 2023Day & Zimmermann acquired Empire Products, Inc. (EPI), a military sewing company based in Yankton, South Dakota, specializing in propellant and charge bags. Acquisition expanded D&Z's munitions manufacturing capabilities. EPI has produced approximately nine million MACS Propellant Bags.
• X-energycoreStrategic or Co-development Partner · 21 July 2022Day & Zimmermann (with Burns & McDonnell) selected by X-energy as constructors for Xe-100 advanced reactor fleet design and deployment. X-energy's Xe-100 is a next-generation high-temperature gas reactor. The partnership follows X-PDM collaborative approach where constructors work alongside the company from design through construction.

Scale indicators10 records

Recent moves6 records

Expansion highlights6 records

Direct peers

• Fluor Corporation: Fluor is a publicly traded EPC and operations & maintenance provider serving power, industrial, mining, and government clients with comparable Maintenance & Construction, mission solutions, and energy transition offerings that overlap directly with D&Z's nuclear/fossil maintenance and government services divisions.
• Babcock & Wilcox Enterprises: B&W designs and services utility-scale and SMR/advanced nuclear steam generating systems and provides environmental and fuel-handling services, directly overlapping D&Z's nuclear maintenance, modification, and ASME Section III nuclear-construction positioning.
• Quanta Services: Quanta is the largest specialty contractor for utility transmission, distribution, and renewable energy infrastructure, mirroring D&Z's power-plant M&M, solar field construction, and Battery Energy Storage Systems offerings for utility and industrial customers.
• Jacobs Solutions: Jacobs provides critical mission solutions, advanced facilities, and cyber/intel services to government and commercial clients, alongside energy and power engineering services that directly compete with Mason & Hanger's architecture/engineering and D&Z's power services lines.
• KBR: KBR delivers government solutions, defense technology, and sustainable technology/energy services; its mission technology and readiness/logistics lines overlap with Day & Zimmermann Government Services (SOC) defense/intelligence work.
• BWX Technologies: BWXT is a leading supplier of nuclear components, fuel, and U.S. Navy and DOE reactor services, overlapping with D&Z's nuclear-qualified maintenance/modifications capability and DOE Reactor Pilot Program adjacency.
• MasTec: MasTec's infrastructure construction segments (Clean Energy & Infrastructure, Oil & Gas, Power Delivery) closely parallel D&Z's fossil construction, solar field, data center, and battery storage project work for enterprise customers.
• AECOM: AECOM is a global infrastructure consulting firm with a federal services and power/industrial practice that competes with Mason & Hanger (architecture/engineering) and D&Z's Maintenance and Construction work for utility and defense clients.

Broad incumbents

• BAE Systems plc: BAE Systems is a large diversified defense prime with munitions, ordnance, and combat vehicle operations (BAE Inc. Land & Armaments) that overlap Day & Zimmermann's artillery/munitions and propellant manufacturing business, though at much greater scale and across broader platforms.
• General Dynamics: General Dynamics Ordnance & Tactical Systems manufactures propellants, projectiles, and precision munitions, competing with D&Z's 155mm M795, propellant bag, and small/medium caliber munitions work; as a broad incumbent it also addresses adjacent defense segments beyond D&Z's niche.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat6 records

Key risks6 records

Key highlights7 records

Customer concentration

• Facebookfacebook.com/dayzim
• Xx.com/DayZim

Compliance2 records

Revenue estimate

Valuation estimate

Number of profiles

Profiles12 records

Subsidiaries9 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A2 records

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Day & Zimmermann