Alabama

Statewide summary — confirm with your building department before designing

Snow load audit, August 2026. No statewide ground snow load could be confirmed for Alabama and both bounds are left NULL. Alabama's statewide minimum residential code is set by the Alabama Energy and Residential Codes Board at Ala. Admin. Code r. 305-2-4-.09, which opens by adopting "The 2015 International Residential Code (IRC) as modified below" and then amends only R302.5.1 opening protection, R313 sprinklers, R322.3.5.1 which is deleted, R324.7.2.2 solar access pathways, the energy chapter, one fuel gas identification rule and the electrical chapters. There is no amendment to R301.2 and no occurrence of the word snow in the rule. Separately the Alabama State Building Code at Ala. Admin. Code ch. 355-12-1, administered by the Department of Finance Division of Construction Management and applying to state jurisdiction buildings, adopts the 2021 IBC with a short list of substitutions drawn from the 2024 IBC, none touching Section 1608, and the word snow does not appear in that chapter either. Neither Alabama code publishes a ground snow load, so Table R301.2(1) is completed by the local building official. What was searched for and not found: a snow amendment in either adopted chapter, both read in full with complete text layers; a state climatic and geographic design criteria table; and an ADECA or DCM snow map. Flagged but not changed: the stored irc_edition of 2021 IRC does not match the adopted statewide residential code, which is still the 2015 IRC under rule 305-2-4-.09; the stored 2021 IBC is correct for the Alabama State Building Code. None of the four existing values was changed. Seismic design category B is retained, and two official determinations conflict, so both are recorded. Under the IRC single parameter table, the method the adopted IRC uses, the USGS ASCE 7-16 design maps web service at Site Class D and Risk Category II gives short period design accelerations of 0.325 g at Florence, 0.325 g at Scottsboro, 0.312 g at Birmingham, 0.279 g at Huntsville and 0.100 g at Mobile, all of which fall in category B except Mobile which falls in A, so B is the statewide maximum by that route. Under the full ASCE 7-16 two parameter method the same USGS service returns category D at Florence, driven by a one second design acceleration of 0.222 g, and category C at Huntsville, Birmingham and Scottsboro. B is kept because it is the governing value under the residential method Alabama has actually adopted, but anyone designing in Lauderdale County or working under the IBC must run the two parameter determination, which can place that corner of the state well above B. The stored ground snow load of 0 psf is a coastal figure with no state source behind it and does not describe the Appalachian foothills in the northeast of the state. No value on this row was changed by this audit, but the wind speed needs care. The 105 mph figure is an ASCE 7 ultimate design wind speed for the interior of the state. Mobile County adopts an ultimate design wind speed of 160 mph for Risk Category II, 148 mph for Risk Category I and 174 mph for Risk Categories III and IV. Wind pressure varies with the square of speed, so a Gulf Coast structure designed to 105 mph would carry well under half the load its jurisdiction requires. Anyone building in Mobile or Baldwin County must use the county adopted value, not this one. Seismic design category B covers Birmingham, Huntsville, Decatur and Florence, where short period design acceleration runs about 0.28 to 0.33 g for Site Class D; Mobile County adopts A. Termite risk of very heavy matches both the Mobile County adopted table and the top band of the IRC termite map. Frost depth of 6 inches corresponds to no adopted Alabama value located in this audit; Mobile County states a minimum footing depth of 12 inches below grade, which is also the IRC minimum everywhere, and northern Alabama jurisdictions go deeper. Winter design temperature of 10 F is colder than the 30 F adopted by Mobile County and appears to be a conservative statewide figure rather than a local one.