The new Vanderbilt University Medical Center Medical Research Building IV will house research programs and staff in a state-of-the-art laboratory facility with over 400,000 ft2 (37,000 m2) of contiguous space. Because no green-field sites with access to campus services and utilities were available on the research campus, the best location was found to be a site containing Langford Auditorium and Light Hall. The existing auditorium was, however, booked for the foreseeable future and had the only 1200 seat auditorium on campus--it could not be closed. Using an innovative post-tensioned concrete truss system constructed around a grouted and post-tensioned steel tube truss that supported the formwork, the design and construction teams were able to span the existing auditorium and still meet strict deflection criteria for the 11 stories of new research area the trusses supported.