South Carolina

Statewide summary — confirm with your building department before designing

Snow load audit, August 2026. No statewide ground snow load could be confirmed for South Carolina and both bounds are left NULL. South Carolina adopted the 2021 South Carolina Building Codes at the Building Codes Council meeting of October 6, 2021, effective January 1, 2023. The Council's state modifications, published as Document No. 5084 in the State Register and codified as Chapter 8 of the South Carolina Code of Regulations, amend IRC Section R301.2.1 for wind and IRC Section R301.2.2.1 for seismic and say nothing whatever about snow. That modification text is government authored and may be quoted: for wind, "Buildings and portions thereof shall be constructed in accordance with the previously published maps by the South Carolina Building Codes Council. The local building official may delineate the wind design category within their jurisdiction provided that it does not surpass those provided on the Applied Technology Council (ATC) website." For seismic, "Buildings shall be assigned a seismic design category in accordance with the previously published maps by the S.C. Building Codes Council." There is no third sentence doing the same for snow. Ground snow load therefore falls back to the model table that the local building official completes, and South Carolina publishes no value. What was searched for and not found: any snow provision in the 36 page 2021 modifications document or in the 53 page consolidated Regulation Chapter 8, both with complete text layers and read end to end; a snow or frost map on the Council's maps page, which offers county wind and seismic maps only, 34 county PDFs plus two counties given as text, and the page carries no snow or frost map at all; and any LLR or other state agency climatic design criteria table. The single occurrence of the phrase maximum snow load in Chapter 8 is a modular building data plate requirement, obliging the manufacturer to state a value rather than the state to publish one, which is the opposite of a state assignment. The stored ground snow load of 10 psf comes from York County's adopted Table R301.2(1) and remains a county figure. It bounds nothing statewide: the upstate is the part of South Carolina most likely to exceed it and no state source caps it. None of the four existing values was changed by this pass; the seismic design category D, wind speed 140 mph, frost depth 12 inches and ground snow load 10 psf all stand as recorded in the earlier audit, with the coastal versus upstate caveats it sets out. Seismic design category corrected from B to D, frost depth corrected from 6 to 12 inches, and ground snow load corrected from 5 to 10 psf. The seismic change is the one that matters most. Charleston sits on the source zone of the 1886 earthquake, one of the most significant historical seismic events in the eastern United States. The USGS ASCE 7-16 design maps service, read at Site Class D and Risk Category II under the IRC single parameter method, returns short period design accelerations of 0.875 g at Charleston, 1.054 g at North Charleston, 1.252 g at Summerville and 0.803 g at Mount Pleasant, every one of which falls in category D. A stored value of B would have left houses across the Charleston metropolitan area braced for a small fraction of the force they must actually resist. Inland South Carolina really is lower, at 0.352 g in Columbia and 0.324 g in both Greenville and Florence, so treat D as the coastal governing case rather than a uniform statewide truth. The frost and snow corrections rest on adopted county criteria: York County publishes a Table R301.2(1) giving 12 inch frost line depth and 10 psf ground snow load, and Calhoun County requires footings 12 inches below undisturbed grade. The stored 6 inches and 5 psf described only the immediate coastal plain and were below the adopted requirement across the upstate and midlands. Wind was left at 140 mph but is emphatically not a state constant. The South Carolina Building Codes Council publishes county wind and seismic maps that show roughly 115 mph over York County, 115 to 120 over Richland County at Columbia, 130 to 140 over Beaufort County, 140 over Berkeley County, 140 to 150 across Charleston County and 150 over Georgetown County, so the seaward strip of Charleston County and all of Georgetown County require more than the stored figure while the whole upstate requires far less. Termite risk of very heavy is right for the coastal plain; the upstate falls in the moderate to heavy band. Confirm your own lot with the local building official. Sources: https://llr.sc.gov/bcc/maps.aspx, https://www.yorkcountygov.com/DocumentCenter/View/6147/Table-R30121-03_2024 and https://earthquake.usgs.gov/ws/building-codes/