The Indianapolis Museum of Art conducted or commissioned scientific and historical research on Lilly House with the goal of restoring the home to its 1930s appearance—the early years of the J. K. Lilly Jr. family's occupancy. The painstaking historic restoration of Lilly House began in 1998 and continued through early 2002.
To lead the project the IMA hired Hillier, a nationally known architecture firm specializing in historic restoration. Hillier ordered diagnostic tests to determine the condition of Lilly House.
Infrared photographs called thermographs were taken to pinpoint major areas of heat loss and provide structural information. The thermographs also revealed the position of original windows that were covered over when Lillys remodeled the home in the 1930s.
Computerized sensors called dataloggers were installed throughout the house to measure humidity levels and their variation. Results showed that humidity levels ranged from 35 to 95 percent within the structure.
Results from the datalogger and thermograph tests helped to determine the type of HVAC system needed to stabilize the home and protect its contents. A new, state-of-the-technology HVAC system was installed in 2000.
Analysis of drainage systems was conducted using boroscopy, a sophisticated technology in which tiny, fiber-optic cameras are inserted in drain lines to record the condition of pipes and determine where they lead. Excavation and replacement of drain lines was required in some cases.
Analysis of building's skin was accomplished by taking core samples of the exterior stucco. Lab analysis revealed the stucco's chemical composition and indicated that the innermost layers were sound. Outer layers required repair and in some areas replacement.
A new slate roof was installed. All windows were removed, restored with original fixtures and reinstalled.
In order to develop a new, lower-level visitor center, the terrace level of the home was partially excavated. Two hundred truckloads of soil were removed.