The stilt house model is a very suitable form to be developed in coastal areas known to experience frequent flooding. In addition, the model is very flexible to create because it saves land and construction costs. In developing space that takes up the area under the house (underneath), the homeowners are different in their implementation but adapt to various things such as the economy, family needs, and space availability. This paper aims to determine the form of changes in the function of space due to the development of family needs related to the material used. Research using phenomenology methodology. The data collection techniques were through in-depth observation, interviewing the community, and distributing questionnaires. Data analysis techniques using descriptive and correlation. Correlation analysis aims to see the relationship between related variables, namely the function of the development space with the material used and the part being developed. After that, a discussion was held to see or relate it to previous research regarding the suitability or incompatibility with the research results. As a result, homeowners generally develop the house by closing the pit, starting from the middle to the back. Generally, the function of the additional space is for service activities. Generally, they also use brick materials, and from the correlation, there is a significant relationship between work, income, and development room. The conclusion is that the development of the kolong space is influenced by the action of residential space requirements due to physical growth and the development of the number of family members and is supported by the economic development of the homeowner.