South Carolina's residential code ties roof wind requirements to the design wind speed for your location. Under the state's version of Section R301.2.1, that speed comes from Table R301.2, which your local jurisdiction fills in. Today the state text refers to the Council's previously published maps. From January 1, 2027, it refers to the ASCE Hazard Tool.
That one number then drives the wind class your shingles need and whether the code's standard wind provisions apply to your house at all. Here is how the pieces connect.
Where does the design wind speed come from?
The model IRC asks each jurisdiction to enter the wind speed from the national map in Table R301.2 (2021 IRC Chapter 3). South Carolina modifies that. Its 2021 R301.2.1 points to "the previously published maps by the South Carolina Building Codes Council." The local building official may delineate wind areas, within limits (2021 modification).
Those maps are on the Council's Wind/Seismic Maps page, approved for the 2021 cycle. The page calls them the primary source for wind and seismic boundaries for one- and two-family homes. The ASCE Hazard Tool helps clarify a boundary but doesn't supersede the maps.
- The Richland County map shows 115 mph lines, one running through Columbia, and a 120 mph line in the southeastern part of the county.
- The Lexington County map shows 115 mph lines.
- Both maps note that the speed applies along each line, and that interpolation between lines is set by the local authority.
For 2024, the state rewrites the same sentence to use the American Society of Civil Engineers (ASCE) Hazard Tool. The local official may delineate wind areas "as long as, it does not surpass those provided" by the tool (IRC 2024 04; State Register, Section 8-1202). Ask your building office which speed it uses for your address.
What wind rating do my shingles need?
Section R905.2.4.1 requires asphalt shingles to be tested to ASTM D7158 and labeled with the class Table R905.2.4.1 calls for. Shingles outside the scope of D7158 are tested and labeled to ASTM D3161 instead. The text and table are the same in the 2021 and 2024 editions.
Asphalt shingle wind classes by design wind speed (IRC Table R905.2.4.1, lower rows)
| Maximum ultimate design wind speed, Vult (mph) | ASTM D7158 class | ASTM D3161 class |
|---|---|---|
| 110 | D, G or H | A, D or F |
| 116 | D, G or H | A, D or F |
| 129 | G or H | A, D or F |
| 142 | G or H | F |
So a house on the 115 mph line falls in the 116 mph row. A house where the local office applies 120 mph falls in the 129 mph row, which narrows the D7158 options to Class G or H. Higher speeds continue up the table in the code text. A table footnote says D7158's standard calculations assume Exposure Category B or C and a building height of 60 feet or less.
Check the label, not the brochure
The code requires the class to appear on the shingle packaging. On inspection day, the wrapper on the roof is what counts.
How must shingles be fastened?
Two rules apply in both editions (2024 IRC):
- Fasteners (R905.2.5): galvanized steel, stainless steel, aluminum or copper roofing nails, at least 12-gauge shank with a 3/8-inch head, meeting ASTM F1667. They must reach at least 3/4 inch into the sheathing, or through it if it's thinner.
- Number (R905.2.6): what the manufacturer's approved instructions require, but at least four per strip shingle or two per individual shingle.
Because the manufacturer's count can be higher than the code floor, ask your roofer what the instructions say for your shingle at your design speed.
What if my house is in a wind-design area?
Under Section R301.2.1.1, the IRC's own wind provisions don't apply where Figure R301.2.1.1 requires wind design. The same goes where the speed reaches 140 mph in a special wind region (2024 IRC). There, the house must be designed with methods such as the Wood Frame Construction Manual, ICC 600, ASCE 7 or the International Building Code.
Those areas also carry stricter underlayment rules in the IRC. For 2024, South Carolina replaces the stricter application rules for asphalt shingles with the ordinary ones. Our underlayment post explains the details. Ask your building office whether your address is in a wind-design area.
Does any of this apply to a re-roof?
Yes. Re-roofing must meet the requirements of Chapter 9 (R908.1), which includes shingle wind classes and fastening. The code edition is set by your permit date under S.C. Code §6-9-130(A). Our 2024 residential code guide covers the transition.
For what wind does to a roof in practice, see our wind damage guide.
Questions to ask your roofer
- What design wind speed does the building office use for my address?
- Which ASTM D7158 or D3161 class does that require, and does the shingle you're quoting carry it on the label?
- How many nails per shingle do the manufacturer's instructions call for at that speed?
- Is my address in an area where wind design is required?
