Today, every South Carolina home is permitted and inspected under the 2021 International Residential Code (IRC) with South Carolina modifications, in force since January 1, 2023. The 2024 IRC with South Carolina modifications takes over on January 1, 2027. For a typical shingle re-roof the changes are modest. The ones that matter touch underlayment, what may stay on the deck during a tear-off, and where your design wind speed comes from.
This guide is for homeowners planning a re-roof in 2026 or 2027, and for builders with permits on either side of the date. Every code statement links to an official source. Those are the SC Building Codes Council at LLR, the State Register, the SC Code of Laws, and the International Code Council's (ICC) free online IRC.
Which residential code is in force in South Carolina right now?
The 2021 South Carolina Residential Code, which is the 2021 IRC as modified by the Building Codes Council. The Council adopted the 2021 codes on October 6, 2021, according to its Building Codes in Effect summary. Local jurisdictions had to begin enforcing them on January 1, 2023. The same summary says every municipality and county must enforce the mandatory codes, and IRC appendices apply only where the Council adopts them.
The state sets the technical rules and local offices enforce them. Administrative rules, such as permit procedures and fees, are each jurisdiction's job and must be adopted by local ordinance. That is why the roof rules are the same in Columbia and Lexington while the permit paperwork is not. Our roof permits guide covers who issues permits, office by office.
When does the 2024 code take effect, and is the date final?
The Council adopted the 2024 IRC and the other 2024 codes with South Carolina modifications on August 26, 2025. Its 2024 Modifications Index says the Council "established the implementation date for local jurisdictions as January 1, 2027." State law lets the Council choose whether a modified code starts on the first day of January or July (S.C. Code §6-9-40).
One- and two-family homes have an extra step. Under §6-9-55, a code change affecting those homes must be issued as a regulation under the state's Administrative Procedures Act. It can't be enforced until that regulation is effective. The 2024 residential changes are Regulation Document No. 5417.
Here is how that played out in 2026. A joint resolution to approve Document No. 5417, S. 1076, was introduced in the Senate on March 31, 2026 and recommitted to the Labor, Commerce and Industry Committee on April 16, 2026. The bill page lists no later action. On May 22, 2026, the State Register (Vol. 50, Issue 5) printed Document No. 5417 in its Final Regulations section.
The stalled resolution didn't block the regulation. S.C. Code §1-23-120(D) covers this case. If no approving resolution is enacted within 110 days of submission, and no committee has introduced one to disapprove, the regulation takes effect on publication in the State Register. The Building Codes Council page now links that May 22 issue as the published 2024 code modifications.
Confirm before you plan around it
Dates like this can still be affected by later legislation or emergency action. For a specific project, ask the office that issues your permit, or contact the Building Codes Council at 110 Centerview Dr., Columbia, (803) 896-4688, Contact.BCC@llr.sc.gov (LLR contact details).
Does the permit date decide which code my roof is built to?
Yes, under state law. S.C. Code §6-9-130(A) says buildings must be inspected under the codes in effect for the locality on the date the original building permit was issued. If no issue date can be found, the date the completed application was submitted is used instead.
In practice, a re-roof permit issued in December 2026 is inspected under the 2021 code, even if the crew arrives in January 2027. A permit issued on or after January 1, 2027 falls under the 2024 code. If your job sits near the line, ask your roofer when the permit will be issued, not only when work will start. Local offices may also publish their own transition notices, so ask the office that covers your address.
Which South Carolina modifications touch roofs?
Four of the residential modifications in the 2024 index affect roofs or roof framing. Two carry over from earlier code cycles, one is reworded, and one is new.
- R905.2.8.5 Drip edge (carried over). South Carolina replaces the IRC's detailed drip edge paragraph with one sentence. Drip edge is required at eaves and rakes of asphalt shingle roofs "where required by the manufacturer." The same modification appears in the 2021 index and dates back to the 2015 cycle. More in our drip edge post.
- Table R905.1.1(2) Underlayment application (new for 2024). For asphalt shingles, the column for areas where wind design is required is changed to match the ordinary requirements. The Home Builders Association of South Carolina proposed it. See underlayment rules in South Carolina.
- R301.2.1 Wind design criteria (reworded). The 2021 state version points builders to wind speeds from the Council's previously published maps. The 2024 version points to the American Society of Civil Engineers (ASCE) Hazard Tool. In both, the local building official may delineate wind areas, within limits. See roof wind requirements.
- R802.10.1 Truss design drawings (carried over). Truss drawings must ship with the trusses and are approved at the inspection rather than before installation. This matters to builders, not to re-roofs.
The final regulation also adopts three IRC appendices for statewide use: BF (patio covers), BO (existing buildings and structures) and BB (tiny houses). It does not adopt IRC Chapter 11 on energy efficiency (Document No. 5417). The 2024 index notes that the 2009 International Energy Conservation Code is South Carolina's energy standard by statute.
What changes in the 2024 IRC itself?
Most roof changes come from the ICC's base code rather than from South Carolina. We compared Chapter 9, Roof Assemblies, of the 2021 IRC and the 2024 IRC section by section on the ICC's free viewer. The table lists the changes that matter on a house, plus the main rules that stay the same.
Roof rules under the current and the next South Carolina residential code
| Roof topic | 2021 IRC + SC mods (now) | 2024 IRC + SC mods (from 1 Jan 2027) | Source |
|---|---|---|---|
| Underlayment types for asphalt shingles | ASTM D226 Type I or II, ASTM D4869 or ASTM D6757. A full layer of self-adhering ASTM D1970 underlayment is allowed as an exception. | The list adds ASTM D1970 and ASTM D8257. A full self-adhering layer becomes one of three standard options in the application table. | R905.1.1 and Tables R905.1.1(1)–(2): 2021, 2024 |
| Underlayment on slopes from 2:12 up to 4:12 | Two layers: a 19-inch starter strip at the eave, then 36-inch sheets lapped 19 inches. | Two layers, written for any sheet width: a half-width starter strip, then full sheets lapped half a sheet plus 2 inches. | Table R905.1.1(2): 2021, 2024 |
| Underlayment on 4:12 and steeper | One layer, shingle fashion, lapped 2 inches; end laps 4 inches, offset 6 feet. | Same, or a single self-adhering layer. | Table R905.1.1(2): 2024 |
| Asphalt shingle underlayment where wind design is required (Figure R301.2.1.1) | Two layers, attached with cap nails in a grid 12 inches apart, with 6-inch spacing at laps. | Base IRC gives three high-wind options. The SC modification replaces that application column with the ordinary requirements; the type and attachment tables are not modified. | Table R905.1.1(2)–(3): 2021, 2024; SC mod IRC 2024 34: State Register |
| Drip edge on shingle roofs | Required at eaves and rakes of asphalt shingle roofs where the manufacturer requires it (SC mod). | Same SC modification, carried over. | R905.2.8.5: 2021 index, 2024 index |
| Eave ice barrier | Required where the local Table R301.2 says YES; runs from the eave to 24 inches inside the exterior wall line (36 inches along the slope on 8:12 and steeper). | No substantive change. | R905.1.2: 2021, 2024 |
| Shingle wind rating | Packaging labeled to ASTM D7158 or ASTM D3161 with the class Table R905.2.4.1 requires for the design wind speed. | Unchanged. | R905.2.4.1: 2024 |
| Where the design wind speed comes from | The Council's previously published maps; the local official may delineate within limits. | The ASCE Hazard Tool; the local official may delineate, not exceeding the tool's values. | R301.2.1: 2021 index, 2024 index |
| Deck under shingles | "Solidly sheathed decks." | "Wood structural panels or solid lumber sheathing." | R905.2.1: 2021, 2024 |
| Closed valleys lined with self-adhering membrane | ASTM D1970 membrane allowed in place of the lining. | Allowed, but the membrane must be at least 36 inches wide. | R905.2.8.2: 2024 |
| Tear-off: what may stay on the deck | Everything comes off down to the deck, except an adhered ice barrier membrane, which may stay under a new one. | The ice barrier exception now requires sound sheathing and both manufacturers' permission. Sound self-adhered underlayment may also stay in limited cases. | R908.3: 2021, 2024 |
| Roofing over an existing roof (recover) | Allowed per the manufacturer's instructions; not allowed over a wet or deteriorated roof, over slate or tile, or where two or more roof coverings already exist. | Same limits, moved to Section R908.4. | R908.3.1 (2021), R908.4 (2024): 2021, 2024 |
| Roof coatings | No separate section. | New Section R909: coatings must meet R902 and R904, follow the manufacturer's instructions and comply with a listed material standard. | R909: 2024 |
| Underlayment under metal roof panels | Per the manufacturer's instructions in areas where wind design isn't required. | New R905.10.6 requires underlayment per R905.1.1, with listed types for panels on solid sheathing. Structural panels that need no substrate or underlayment are exempt. | R905.1.1, R905.10.6: 2021, 2024 |
Several rules a homeowner might expect to change did not. These read the same in both editions of the ICC code text: shingle fastener specs (R905.2.5), four fasteners per strip shingle (R905.2.6), the 2:12 minimum slope (R905.2.2) and the base drip edge text.
What does this mean for a re-roof versus new construction?
For a re-roof
For most shingle re-roofs, practice changes little. Underlayment on a typical slope is still one lapped layer. Shingles still need the wind class for your design speed. Drip edge still follows the shingle manufacturer's instructions.
Tear-off rules are where you may notice a difference. Under the 2021 text, only an adhered ice barrier membrane may stay on the deck. Under 2024, some self-adhered underlayment may stay too, but only over sheathing that isn't water soaked or deteriorated. That puts weight on a careful deck check during tear-off. We explain the limits in roofing over shingles under the SC code.
If you are switching from shingles to metal roof panels, ask about underlayment. The 2024 edition adds a direct underlayment requirement for metal roof panels that the 2021 edition left to the manufacturer in most areas.
For builders
New homes pick up the reworded wind criteria, the state's underlayment change for high-wind areas, the truss drawing rule and the three adopted appendices. Energy requirements still come from the 2009 IECC by statute rather than IRC Chapter 11. Permits issued before January 1, 2027 stay under the 2021 code for inspection, per §6-9-130.
Why does the local Table R301.2 matter for my roof?
The IRC leaves local climate data blank. Section R301.2 says additional criteria "shall be established by the local jurisdiction and set forth in Table R301.2" (2024 IRC Chapter 3). The table has columns for design wind speed, special wind region, windborne debris zone and "ice barrier underlayment required."
Footnote h tells each jurisdiction to enter YES where there has been a history of local damage from ice damming, and NO otherwise (2021 IRC Chapter 3). We haven't found a published Table R301.2 for Columbia, Richland County or Lexington County. So we don't state whether an eave ice barrier is required there. Ask the building office that issues your permit for its Table R301.2 entries.
For wind, the Council's Wind/Seismic Maps page posts county maps approved for the 2021 cycle. 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. The map notes say interpolation between lines is up to the local authority.
Questions to ask your roofer about the code change
- Which office issues the permit for my address, and on what date do you expect it to be issued?
- Will the job be inspected under the 2021 or the 2024 South Carolina Residential Code?
- What does the local Table R301.2 say about ice barrier and design wind speed at my address?
- Which wind classification does that speed require, and is it printed on the shingle packaging you plan to use?
- Does the shingle manufacturer require drip edge, and is new drip edge in the quote?
- Is this a full tear-off or a recover, and how many roof coverings are on the house now?
- If you plan to leave any existing self-adhered underlayment in place, why, and do both manufacturers allow it?
- If you find wet or soft decking, how is that handled in the written contract?
Cola City Roofing works across Columbia and the Midlands. If you're planning a roof replacement around the code change, we can tell you which office covers your address and which edition your permit is likely to fall under.