As we enter into hurricane, many people ask, “How can I build to mitigate hurricane damage?” Historically, we have worried more about hurricanes with high winds but Hurricane Florence proved that category 1 storms can be just as disastrous. Eight people in South Carolina died, property damage was over $607 million, and more than 2,000 homes were lost to flooding.

When building a new house there are three critical concerns in the design and construction in hurricane prone areas that address the simultaneous impacts of wind, rain, and flooding.

Keep the building from blowing away

The building must be tied together from the roof rafters to the foundation. The most common method employs hurricane clips and tie rods. The building must be designed to withstand wind shear which can be accomplished with plywood sheathing if there are limited amount of openings in the walls. Walls with large openings often require steel framing to withstand the wind shear.

Windows and doors need to be protected from flying objects. The simplest but not the cheapest is to install impact rated windows and doors. Other options include hurricane rated shutters, PVC coated woven fabric such as Wayne Dalton’s Fabric-Shield® or plywood panels cut to fit the openings and fastened as per the building code.

The exterior finishes should be rated to withstand hurricane force winds and be installed securely to the structure as per the manufacturer’s recommendation to meet the tested installation.

Keep the rain out

Keeping rainwater out of the building is fairly straightforward but only if design decisions are made to address it. As the building scientist William Rose observed, “If it doesn’t get wet…it can’t leak.” Thus, large overhangs help keep the building dry by reducing the amount of water flowing down the walls by a minimum of 50%.

Field experience shows that water leakage around doors and windows is very common. Therefore, sill pans and flashing are essential. Flashing has two distinct purposes; it keeps water from getting into the wall through joints and it guides water back out of the wall when some leakage does occur.

All exterior cladding will allow some moisture to pass through. The best way to capture the water and direct it out of the wall system is with a drainage plane which is a waterproof layer on the exterior of the wall sheathing. For the drainage plane to work correctly there is an air gap to promote drying. Likewise, a secondary roofing membrane will keep water out if the primary roof material is compromised.

Crawl spaces must be sealed against water leakage, humid air infiltration and vapor permeation from the earth. Closed crawl spaces do not have vents to the exterior. They are insulated at the perimeter wall.

Drain water away from house by using gutters and sloping the ground away from the building.

Prevent flood damage

The most important consideration is to elevate the structure and mechanical systems to minimize its contact with flood water and a potential storm surge. The new flood maps that will soon be adopted in Beaufort County are lowering the flood heights in many areas. It may be prudent to place your house at the current higher requirement because of rising sea levels.

Crawl spaces located in a flood zone need hydro-static vents to prevent flood waters from collapsing foundation walls. The hydro-static vents will allow flood water to enter and exit the crawl space. Charleston based Flood Flaps® provide a tight seal for a closed crawl space.

Finally, use materials that tolerate soaking and can easily dry.