Additions Additions - increase the square footage or external dimensions of a building. They can be divided into lateral additions, vertical additions, and enclosures of areas below existing buildings. When considering additions, it is important to consider that changes to the shape of the building may impact the potential damages to the house. A lateral addition may change the way flood waters travel around the structure and potentially create obstructions for flood-borne debris that may require additional foundation modifications. Vertical additions may also impose greater loads on the existing structure. A qualified design professional should evaluate the loading to the entire structure to see if additional structural modifications are required in order to maintain the structure’s ability to sustain flood