Mississippi

Statewide summary — confirm with your building department before designing

Snow load audit, August 2026. No statewide ground snow load could be confirmed for Mississippi and both bounds are left NULL, because Mississippi has no statewide design criteria at all to publish one in. Under Senate Bill 2378 of the 2014 Regular Session, codified in Miss. Code Title 17 Chapter 2, a county or municipality that enforces building codes must adopt at minimum one of the last three adopted editions of the International Building Code or the International Residential Code together with any amendments made by the Mississippi Building Codes Council, may adopt codes not less stringent than that minimum, and was given a 120 day window after the section took effect to opt out of the requirement entirely. The governing edition therefore varies by jurisdiction, some jurisdictions enforce nothing, and the state assigns no ground snow load, wind speed, frost depth or seismic category of its own. What was searched for and not found: a Mississippi Building Codes Council amendment addressing R301.2, Table R301.2 or Section 1608; a State Fire Marshal or Insurance Department design criteria publication; and any state snow map. The Insurance Department's Uniform Building Codes page carries only the SB 2378 opt out reporting form and contains no design criteria, and the bill text itself contains no wind, snow, seismic or frost provision. Table R301.2 is therefore completed by whichever local official is enforcing. The stored ground snow load of 0 psf is a coastal plain figure with no state source behind it and bounds nothing in the north of the state. Seismic design category corrected from A to D. This is the same New Madrid exposure already corrected on the Tennessee row and it was left standing here. The USGS ASCE 7-16 design maps web service at Site Class D and Risk Category II returns short period design accelerations of 0.646 g at Southaven, 0.556 g at Tunica, 0.417 g at Corinth, 0.411 g at Clarksdale and 0.405 g at Oxford. Under the full ASCE 7-16 method the service returns category D outright at Corinth, Clarksdale and Oxford; at Southaven and Tunica it declines to return a category because the one second site coefficient there requires a site specific ground motion analysis, which is a statement that the hazard is high, not that it is absent. Under the IRC single parameter table Southaven and Tunica fall in D0 and Corinth, Clarksdale and Oxford in C. Both readings are recorded here and D is the value stored, as the statewide governing category and to match how the Tennessee and South Carolina rows are written; DeSoto and Tunica counties are specifically D0 under the residential method and require a site specific determination under ASCE 7-16. A stored A was untenable for a state whose northwestern counties sit on the highest seismic hazard east of the Rocky Mountains. Southern Mississippi genuinely is low, with Jackson at 0.148 g, which is category B under the IRC table, so D is the governing case and not a uniform statewide truth. Wind speed 160 mph, ground snow load 0 psf and frost depth 6 inches were not changed by this pass. Ultimate design wind speed corrected from 120 to 160 mph by audit. Under ASCE 7-16 at Risk Category II the three Gulf coast counties require about 158 to 161 mph: Gulfport 160, Biloxi 160, Pascagoula 161 and Bay St Louis 158. The stored 120 mph under-designed that entire coast, roughly 370,000 residents, by about 40 mph, which is near a doubling of design wind pressure. Inland Mississippi is far lower: Hattiesburg is about 131 mph, Meridian 114, Jackson 110, Tupelo 106 and Southaven 105. The value published here is the governing coastal contour, deliberately conservative, and it is not the requirement at Jackson or in north Mississippi. A site lookup is mandatory in both directions. No other value on this row was changed, but two of them are wrong in the north of the state. Seismic design category A holds for Jackson and the Gulf coast, but north Mississippi sits on the New Madrid zone: Southaven and DeSoto County band to D0, and Corinth, Oxford and Clarksdale to C or D, under ASCE 7-16 at Site Class D and Risk Category II. Anyone building in DeSoto, Alcorn, Lafayette or Coahoma counties must run a site-specific seismic determination and must not rely on the A shown here. Ground snow load 0 psf holds on the coast; Jackson is 5 psf and north Mississippi 10 psf, though the IRC minimum roof live load governs at those levels. Frost depth 6 inches is set locally and was not verified against any government source. The winter design temperature is ASHRAE data, is not published by any Mississippi authority, and is unverified.