The prominent architecture firm NBBJ recently found itself tied up in a series of cases regarding an outbreak of Legionnaires’ disease in Dayton, Ohio. Their story underscores some thorny legal issues for architects and building engineers.

In May 2007 Ohio’s Miami Valley Hospital (MVH) and its corporate arm, Premier Health Partners (PHP), hired NBBJ to lead construction of its new 12-story, modular Heart Patient Tower. Four years later Legionnaires’ disease broke out, sickening 11 patients. One later died.

The Legionnaires’ outbreak was traced to the building’s plumbing system. MVH and PHP’s attorneys suggest the outbreak was linked to the plumbing system during construction—court documents allege the hot water system’s temperature was set too low, or that there was stagnant water in the pipes during construction, or the prefabrication process caused parts of the building to be left exposed too long. It is not clear whether modular construction methods or design had anything to do with the Legionnaires’ outbreak. The courts did not determine negligence, but rather ruled on the design and construction contracts.

“It may prove fiendishly difficult to prove how Legionella formed in the plumbing system,” said architect Richard L. Zimmerman, who was not associated with this case but specializes in expert witness testimony related to construction defects and architectural negligence.

Last year the case went to court. MVH’s argument was that NBBJ failed to procure commercial general liability insurance that protected NBBJ and the hospital from “bodily injury caused by a biological agent or bacteria,” i.e. Legionella.

NBBJ appealed the initial Montgomery County Common Pleas Court decision. On January 16, the Ohio Second Court of Appeals judged in favor of MVH. Judge Mary C. Donovan found NBBJ, who declined to comment for this story, in breach of contract for not procuring an insurance policy that complied with the contract.

For Zimmerman, it is evidence of the complexity of an architect’s job, which intersects in sometimes unexpected ways with a design company’s legal liability. “One can reasonably ask: What should an architect be expected to know about Legionella?” he said.

Nonetheless, Zimmerman said, the ruling sends a message to architects: “Architects must continually consider how to best protect themselves, and how to stay out of litigation.”