With the objective of developing guidelines for a flexible-industrialized housing system. that is, one capable of transforming in consonance to changing family lifestyles, a survey was conducted on 150 houses that had undergone modification. The purpose was to determine why, after how many years, and how houses are modified. Modifications were classified into patterns and were correlated with socioeconomic data from each family. In addition to providing realistic information on how houses can be modified, results showed that certain socioeconomic factors have stronger relationships with specific patterns leading to the hypothesis that patterns can be analyzed and planned independently.