Find your home’s wind speed zone
By Claudette Reichel
LSU AgCenter Housing Specialist
2020 has been an incredibly active and destructive hurricane season. While hurricanes are inevitable, some of the destruction is preventable.
Homes can and do withstand strong hurricanes if they are designed and reinforced for the wind hazard speed of the area. That is most effectively done in new construction, but existing homes can still be strengthened, especially during restoration after storm damage or when remodeling.
In any case, knowing the “wind design speed” for your location is important to specify the level of protection and products that will protect your home in future hurricanes.
Wind loads and construction standards developed by the American Society of Civil Engineers (ASCE) are referenced and illustrated in wind design maps in building codes.
Louisiana first adopted a statewide uniform residential building code shortly after Hurricane Katrina, and the version now in effect for single-family homes is based upon the 2015 International Residential Code (IRC), with some Louisiana amendments. The IRC can be found online at www.iccsafe.org.
An easy way to find the current wind design speed and other hazard information for your home address or city is a great new and free online “Hazards by Location” search tool developed by the Applied Technology Council (ATC).
An example search result for Lake Charles, Louisiana, shows the wind strength design speed for homes in Risk Category II is 131 mph.
You can find your wind speed zone on the Hazards by Location website https://hazards.atcouncil.org/#/.
— Enter your address and click on the Wind box. That will produce a map and wind design speeds for various categories.
— Scroll through the dropdown bar on the left side to the ASCE 7-10 list (applicable for the 2015 IRC adopted by Louisiana) and click Risk Category II — the category for residential structures.
— That will add wind speed contour lines on the map and provide the exact wind design speed for your location.
— There will be a highlighted note if your location is in a "wind-borne debris region" that requires impact protections for windows and doors.
— The map will also show the ground elevation above sea level at the location point.
You can go online to the LSU AgCenter Flood Map Portal at www.lsuagcenter.com/floodmaps to find your home’s Base Flood Elevation (BFE) according to the FEMA flood map to compare with the ground elevation. It’s wise to elevate your home and equipment 2 to 3 feet higher than the BFE because flood insurance premiums are lower and many floods exceed the BFE level.
Keep these tips in mind:
— South Louisiana is in a hurricane hazard zone. The closer to the Gulf, the higher the wind risk. A house in an unobstructed open clearing or within 1,500 feet of open water is susceptible to higher wind forces from unobstructed winds.
— High winds put great forces on a building, including shear loads that cause racking, opposing lateral loads that push and pull on opposite sides, and uplift on the roof. Wind loads increase around corners. Structural sheathing and hurricane hardware connectors that provide a continuous load path from roof to foundation are used to resist those loads.
— The most common loss from hurricanes is roof damage. Properly installed wind-rated roofing systems can survive hurricane-force winds. Specify a rating that exceeds your wind design speed. Shingles rated as Class H or Class F are now readily available and meet the highest wind design code requirements. You can find additional important fortified roof features to specify at www.disastersafety.org.
— Broken windows, doors and garage doors can result in internal loads that amplify wind forces and increase the risk of structural damage. If your home is in a wind-borne debris zone, invest in either impact-rated windows, doors and garage door, or add impact-rated external protections, such as certified hurricane shutters, impact screens and removable panels.
More information about creating a resilient, high-performance home for Gulf region climate and natural hazards is available at the LSU AgCenter LaHouse Resource Center on the LSU campus in Baton Rouge (currently by appointment only).
Other sources of Louisiana information are on the My House/My Home section of www.lsuagcenter.com/LaHouse and on www.youtube.com/mylahouse.
LaHouse is an educational demonstration house and outreach program of the LSU AgCenter. Call 225-578-7913 to schedule your time to explore its many features, cut-away reveals, exhibits, resource library and free publications.
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