What is another word for sub-structure?
Pronunciation: [sˈʌbstɹˈʌkt͡ʃə] (IPA) 
The term "sub-structure" refers to the underlying or foundational elements of a larger structure such as a building or a bridge. Some synonyms for this word include "foundation," "footing," "base," "subfoundation," "subgrade," and "substratum." Each of these words describes the fundamental components that support the weight and structure of a building or other construction. These sub-structures are typically made of concrete, steel, or other durable materials that can withstand the weight and pressure of the larger structure. In engineering and construction, the quality and reliability of the sub-structure are critical to the overall strength and longevity of the finished project.
