Double Trouble

During a hurricane, your building does not get flood OR wind. It gets both at the same time. The building code requires you to design for the combined effect. When you elevate a building to avoid flooding, you expose it to higher wind loads because it is now taller and has open area below. The two hazards interact and must be engineered together.

BFE varies by exact location. Coastal areas typically have BFE between 8 and 14 feet. You can find your BFE on the FEMA flood maps or by contacting Palm Beach County building department. Most builders add 1-2 feet above BFE for safety margin and better insurance rates. Our calculator looks up the BFE automatically based on your address.

Breakaway walls are required in VE zones and recommended in Coastal AE zones. These walls are designed to collapse under flood forces without damaging the main structure. In regular AE zones, you have more options including dry flood-proofing for non-residential buildings. The key is that nothing below BFE should resist flood forces in a way that could transfer damage to the main building.

When you raise a building on stilts or pilings, wind can now hit it from below as well as the sides. The open area under the building creates uplift forces. Plus, the effective height of the building is now measured from ground level to roof, not from the elevated floor. A 2-story building elevated 10 feet behaves like a 3-story building for wind load purposes. This increases both lateral and uplift forces significantly.

In VE and Coastal AE zones, you typically need deep pile or pier foundations that can resist both uplift from wind and scour from floodwaters. The piles must extend below the expected scour depth, which can be 6-10 feet or more in coastal areas. Standard spread footings are not allowed in these zones. A licensed engineer must design the specific foundation for your site conditions, combining flood, wind, and soil factors.