O’Donnell & Naccarato is a creative consulting structural engineering firm operating nationally to support the entire building lifecycle.

Our structural engineers and restoration professionals leverage 65 years of experience to design new buildings, renovations, retrofits, expansions, and structural restorations of all types and levels of complexity. As a partner to design professionals and building owners, our objective is to enhance each facility’s value and extend its useful life. O&N serves clients in 40+ states from offices in Philadelphia, Bethlehem, Mountainside, and New York City.



New Buildings

  • Structural Design
  • Master Planning
  • Parking / Functional Design
  • Seismic Evaluation
  • Feasibility Study
  • Value Engineering
  • Peer Review

Existing Buildings

  • Adaptive Reuse
  • Additions
  • Vertical Expansion
  • Interior Renovation
  • Fit-out
  • Condition Assessment
  • Emergency Response

Facades / Garages

  • Condition Assessment
  • New York City / Philadelphia Inspection Oridinance Assessment
  • Historic Preservation
  • Restoration Design
  • Repair Design
  • Project Budgeting
  • Value Engineering


  • Healthcare
  • Education
  • Multi-Family / Mixed-Use
  • Workspace
  • Retail
  • Hospitality
  • Parking
  • Industrial / Self-Storage
  • Community

Past & Present

photo: O&N Founders William O'Donnell and Peter Naccarato, May 1988

William F. O’Donnell (left) and Peter A. Naccarato, May 1988

O&N’s predecessor Seymour Greenberg opened in Philadelphia in 1954 later welcoming William O’Donnell and Peter Naccarato as Principals. In 1981 the firm became incorporated and adopted its current name setting a foundation for national growth. Today O&N’s Philadelphia headquarters is supported by Mid-Atlantic branch offices and O’Donnell & Naccarato Structural Engineers, a Manhattan-based corporate affiliate founded by four senior O&N Principals to serve structural design and restoration projects in New York State.


We take pride in our close-knit, familylike culture. Our team consists of talented individuals with wide ranging skills from various backgrounds. O’Donnell & Naccarato is an Equal Opportunity Employer and has been recognized as the 5th Best Structural Engineering Firm to Work For in North America. We are always interested in hearing from motivated people who share our passion for creative engineering and peerless service. If you are interested in O&N, please submit your cover letter and resume.