About Us



Thomas Downey, Ltd. (TDL) is a specialty consulting engineering firm providing assessment of existing buildings and structures. We analyze building conditions, identify and evaluate defects, perform forensic investigations, develop repair and restoration plans, and assist property owners in planning and capital budgeting.

Established in 1979, the firm has become one of the most trusted resources for researching and analyzing building conditions and resolving related performance problems in the Metropolitan Washington, DC and the Mid-Atlantic areas. All major building community stakeholders – owners and managers, community associations, law firms, insurance companies, developers, and contractors – rely on the TDL engineering team.

TDL provides a comprehensive menu of services, including building investigation and condition assessment, warranty and reserve study preparation, repair design, expert witness and litigation technical support, and cost estimating.

The firm’s engineers are registered to practice in the District of Columbia, Maryland, and Virginia.

Memberships & Affiliations

Thomas Downey, Ltd. and its staff are active in engineering and client-related organizations. The firm’s members are frequent contributors to the educational programs of Metropolitan Washington, DC chapters of national organizations. In addition, TDL’s Office Manager is a long-term volunteer member of a local board of architectural review. The groups we belong to or regularly participate in their programs include:

American Architectural Manufacturers Association (AAMA)
American Concrete Institute (ACI)
American Forest and Paper Association (AF&PA)
American Institute of Architects Northern Virginia Chapter (AIANOVA)
American Society of Civil Engineers (ASCE)
ASTM International (ASTM)
Association for Preservation Technology International (APTI)
Building Enclosure Technology and Environment Council (BETEC) of the National Institute of Building Sciences (NIBS)
Community Associations Institute (CAI)
Construction Specifications Institute (CSI)
Institute of Real Estate Management (IREM)
International Code Council (ICC)
International Concrete Repair Institute (ICRI)
National Roofing Contractors Association (NRCA)
Structural Engineering Institute (SEI)
Structural Engineers Association (SEA)
Structural Engineers Association of Metropolitan Washington (SEA-MW)
Washington Metropolitan Chapter Community Associations Institute (WMCCAI)


Our Team

Stephen A. Johnston, Ph.D.

Stephen A. Johnston, Ph.D.

Vice President

TDL Vice President, Steve, is a consulting engineer for roofing, waterproofing, exterior walls, masonry, failure investigation, materials assessment, and property condition assessment. He provides technical oversight of roof repair and replacement and performs failure investigation for insurance claims. Steve’s comprehensive and longstanding interest in building design and construction extends to his personal hobbies. He is an enthusiastic collector of roofing memorabilia and antique tools of the trade as well as an avid reader of books focused on building crafts and the practical physics related to building construction. An active volunteer with Boy Scout groups in Maryland, he also shares his passion for building, its methods, and tools with youth. Steve earned his B.S., M.S., and Ph.D. in Materials Science and Engineering from The Johns Hopkins University.

Christopher J. Kelley, LEED Green Assoc.

Christopher J. Kelley, LEED Green Assoc.

Senior Engineering Associate

With 20+ years of experience in the building repair and restoration industry, Chris provides consulting services for building owners on a wide variety of building envelope and property issues. His areas of experience and expertise include long term planning, including reserve studies and budgetary consulting, window evaluation and replacement, historic wood window evaluation and restoration, leak investigation and repair, waterproofing and coatings, masonry evaluation and restoration, concrete evaluation and repair, exterior cladding evaluation, repair and replacement, historic buildings, asphalt paving evaluation, maintenance planning, and repair. He has degrees in Economics and Engineering, a professional certification in historic preservation, and regularly attends relevant continuing education courses and seminars.

Jillian F. Dlugos, P.E.

Jillian F. Dlugos, P.E.

Engineering Associate

Jillian, started her career as a Project Engineer with ExxonMobil, where she had sole ownership and final responsibility for capital engineering projects under $5M. She was the primary engineer for projects through all stages: benefit to cost calculations and justification, funding, design, contractor selection, construction, and commissioning planning / design and execution. Jillian brings her passion for all facets of engineering to provide unique perspective and technical expertise to all her projects. Jillian earned her B.S. in Mechanical Engineering with a minor in Business Administration from North Carolina State University. She is a licensed Professional Engineer (PE) in Virginia, Maryland, and the District of Columbia.