Construction below flood levels, within regulated flood zones, must utilize flood resistant materials.
In the FEMA publication, there’s a handy reference chart to quickly determine which materials are considered acceptable and those that aren’t. Start with Table 1 on page 4 Class Descriptions of Materials. Then compare the different classes with the list of materials on Table 2, on pages 7 to 11.
Additionally, this publication has a wealth of related materials and methods information.