Comparative Review and Assessment of Various Flood Retrofit Methods for Low-Rise Residential Buildings in Coastal Areas

Abstract

Recent hurricanes indicated that retrofitted residential buildings are still susceptible to wind- and flood-induced damage in coastal areas. This poor performance indicates that flood retrofit methods need to be evaluated in terms of efficiency and effectiveness to resist hurricane wind and flood loads. This paper discusses various aspects in the hurricane-resistant design and retrofit of coastal residential buildings, including potential wind and flood-induced damage, risk mitigation, cost of retrofit methods, and the need for better standards. The cost analysis is performed for a typical one-story wood-frame residential building with a gable roof system considering several flood retrofit methods. The result indicates that selecting a flood protection level higher than the basic 100-year flood level can significantly decrease the risk of damage. This result seems appropriate and essential for specific hurricane-prone regions considering recent changes in the intensity/frequency of storms. A review of actual damage types indicates that wood-frame elevated houses are susceptible to experiencing wind-induced damage to the structural system and more extensive damage to the envelope system. The performance of breakaway walls below the base flood elevation (BFE) strongly depends on the connections between such walls and structural members. The result of cost analysis indicates that the foundation type can directly affect the total cost of retrofit solutions, such as elevation, wet, and dry methods for houses in coastal areas. Regarding the elevation method, adding a freeboard higher than the BFE does not significantly increase the total cost once the elevation method is selected as the preferred retrofit solution.