During a hurricane isn't it safer to be in a house on-grade than a house on stilts?
"Non Engineer" Answer: Not necessarily
Explanation: Stilt construction can be found along the coast as well as inland along rivers or wetlands. If you see a house on stilts, there is a reason: flooding! FEMA sets minimum finished floor elevations for all new construction. These requirements change from year to year depending on what FEMA deems "safe" during a flood event. Inland structures that have been built on stilts are typically designed for 100-year flood conditions. That's to say, the finished floor elevation has been set above the highest flood level that has occurred within the last 100 years. Inland flood levels are typically affected by seasonal conditions and not storm events.
During a hurricane event, storm surge is a major concern for barrier island structures as well as structures within the vicinity of the coast. Houses built "on-grade" (or with a foundation that rests on the ground itself) in these areas will be subject to flooding. However, flooding does not cause the most damage during storm events. The significant damages come from wave impact on the exterior walls of a structure. These impact forces can rip a structure off of its foundation or knock it down completely. A structure built on stilts provides less resistance to the moving waters of storm surges. The space between the vertical stilts will allow water to pass by without building up the high impact forces a solid wall sees. Therefore, a structure that has been properly built and secured to a stilt foundation has a higher probability of surviving a hurricane event.
Commentary: All structures are susceptible to damage during a storm event. Just because a structure has been built to meet current code requirements does not ensure that it will survive a storm event. Therefore IF AN EVACUATION ORDER IS ISSUED FOR YOUR AREA… EVACUATE.
"Non Engineer" Answer: Not necessarily
Explanation: Stilt construction can be found along the coast as well as inland along rivers or wetlands. If you see a house on stilts, there is a reason: flooding! FEMA sets minimum finished floor elevations for all new construction. These requirements change from year to year depending on what FEMA deems "safe" during a flood event. Inland structures that have been built on stilts are typically designed for 100-year flood conditions. That's to say, the finished floor elevation has been set above the highest flood level that has occurred within the last 100 years. Inland flood levels are typically affected by seasonal conditions and not storm events.
During a hurricane event, storm surge is a major concern for barrier island structures as well as structures within the vicinity of the coast. Houses built "on-grade" (or with a foundation that rests on the ground itself) in these areas will be subject to flooding. However, flooding does not cause the most damage during storm events. The significant damages come from wave impact on the exterior walls of a structure. These impact forces can rip a structure off of its foundation or knock it down completely. A structure built on stilts provides less resistance to the moving waters of storm surges. The space between the vertical stilts will allow water to pass by without building up the high impact forces a solid wall sees. Therefore, a structure that has been properly built and secured to a stilt foundation has a higher probability of surviving a hurricane event.
Commentary: All structures are susceptible to damage during a storm event. Just because a structure has been built to meet current code requirements does not ensure that it will survive a storm event. Therefore IF AN EVACUATION ORDER IS ISSUED FOR YOUR AREA… EVACUATE.
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