Windows Code Requirements in Tennessee

State with significant severe hail frequency per NOAA SPC storm reports. Insurance restoration contractors should document pre-existing hail damage and recommend impact-resistant materials.

The Central Basin of Middle Tennessee is underlain by Ordovician-age limestone that is highly susceptible to dissolution, creating one of the most karst-prone regions in the southeastern United States. Davidson County (Nashville) has thousands of documented sinkholes. The Central Basin extends through Davidson, Rutherford, Wilson, Williamson, Maury, Marshall, Bedford, Coffee, Cannon, DeKalb, Smith, Trousdale, and Macon counties. Sudden collapse sinkholes can open without warning, and underground drainage conduits may not align with surface topography.

West Tennessee counties within the New Madrid Seismic Zone are assigned Seismic Design Categories D0 through D2 per IRC Table R301.2(1) and ASCE 7-22. The New Madrid fault system is one of the most significant seismic hazards in the eastern United States. SDC D2 (highest risk): Tipton County, Lake County. SDC D1: Shelby County (Memphis), Dyer County. SDC D0: Lauderdale County, Obion County. Liquefaction risk is elevated near Reelfoot Lake and along the Mississippi River floodplain in unconsolidated alluvial soils.

West and Middle Tennessee are located within "Dixie Alley," a region of the southeastern United States with high tornado frequency and intensity. Notable events include the March 2020 Nashville EF-3/EF-4 outbreak (25 fatalities, $1.6 billion damage), the April 1998 Nashville EF-5, and the February 2008 Super Tuesday outbreak affecting multiple counties. Design wind speeds per ASCE 7-22 range from 115-120 mph Vult for Risk Category II structures. All 95 Tennessee counties are at some tornado risk, but West and Middle Tennessee have the highest frequency.

Areas designated as Zone A, AE, V, or VE on FEMA Flood Insurance Rate Maps along the Mississippi River and its tributaries in West Tennessee. Shelby County (Memphis), Tipton County, Lauderdale County, Lake County, Obion County, and Dyer County have significant Mississippi River flood risk. The 2011 Mississippi River flood was the largest flood in the Memphis area since 1937. NFIP participation required for federally-backed mortgages in SFHA.

FEMA-designated flood hazard areas along the Tennessee River and its major tributaries. The Tennessee River flows through East and West Tennessee, affecting Hamilton County (Chattanooga), Loudon County, Roane County, Meigs County, Rhea County, Marion County, Hardin County, Decatur County, Benton County, and Henry County. TVA dam system provides flood control but does not eliminate risk. Tributary flooding from the Hiwassee, Clinch, French Broad, Holston, and Little Tennessee Rivers also creates SFHA areas.

FEMA-designated flood hazard areas along the Cumberland River and its tributaries in Middle Tennessee. Davidson County (Nashville) experienced catastrophic flooding in May 2010, with 11 fatalities and $2 billion in damage. The Cumberland River, Harpeth River, Stones River, and Mill Creek corridors have extensive SFHA designations. Affected counties include Davidson, Sumner, Wilson, Smith, Trousdale, Jackson, Putnam, Montgomery, Robertson, Cheatham, Dickson, Humphreys, and Stewart.

Following the November 2016 Chimney Tops 2 wildfire that killed 14 people and destroyed over 2,400 structures in Gatlinburg and surrounding areas, Sevier County and its municipalities adopted WUI code provisions based on the International Wildland-Urban Interface Code (IWUIC). The WUI zone encompasses portions of Gatlinburg, Pigeon Forge, Sevierville, and unincorporated Sevier County adjacent to the Great Smoky Mountains National Park. This was the deadliest wildfire in the eastern U.S. in a century.