Significant Changes to the 2018 International Residential Code
Andy Barber

The 2018 IRC has been promulgated by the S. C. General Assembly and the 2018 I-codes will go into effect on January 1, 2020. I want to thank all those who worked for more than a year and a half to review the codes and make and fight for suggested modifications. The HBASC has lead in the discussion and proposal of our state code modifications. This article will review the key changes and modifications between the 2015 and 2018 ICC Codes that may affect the way our members build. Included are changes that have been approved and benefit the construction industry and those that members need to be aware of. This is not a comprehensive collection of all of the changes that were made to the 2018 I-Codes.

Significant Changes and Continued Modifications to the 2018 International Residential Code


• ACCESS (TO). In the 2018 IRC: ACCESS (TO) is defined; That which enables a device, appliance or equipment to be reached by ready access or by a means that first requires the removal or movement of a panel, door or similar obstruction.

• CRAWL SPACE. An underfloor space that is not a basement.

Sections 301.2 and 301.2.2.1-Wind & Seismic Maps. The HBA of SC supported a study to be funded by the S. C. General Assembly and produced by The Citadel to review and address the probabilistic hazard maps. This will ensure that houses in S. C. are built on the needs and hazards of our state.

Section 301.2.1.2 Protection of openings. This change replaces 2-story limit on use of wood structural panels for wind-borne debris protection with limit based on 45-foot mean roof height.

Section 302.1 Exterior Walls. This modification maintained the minimum fire separation distance for improvements constructed on a lot where the local governing authority has prior to the implementation of IRC 2012.

Section 302.5.1 Opening Protection. The existing modification was maintained to remove the use of a self-closing device.

Table R311.7.3 VERTICAL RISE. The maximum vertical rise not requiring a landing was changed from 147” to 151”.

Sections R312.2, R312.2.1 and Section R312.2.2 Window Fall Protection. Deleted without substitution.

Section 313 One-and -Two Family Dwellings Automatic Fire Systems. This modification maintains that residential fire sprinklers continue to be an option, but are not mandated.

SECTION R314.4 Smoke Alarms Interconnection. The section exemption for interconnection of smoke alarms for remodeling has been removed. Now any project requiring smoke alarms no matter the scope MUST have interconnected alarms throughout. • Section: R317.1.1 Field Treatment. Field-cut ends, notches and drilled holes of preservative-treated wood shall be treated in the field in accordance with AWPA M4 or in accordance with the preservative-treated wood product manufacturer’s recommendations.

Section R318.1 Protection Against Subterranean Termites. This modification adds an additional method to allow treatments to be conducted under the S. C. Pesticide Control Act and enforced by the Clemson University Department of Pesticide Regulation.

Section R318.4 Foam Plastic Protection. This modification adds language to allow foam plastics to provide an inspection gap for crawlspace applications.

Section: R319.1 Address Identification. The section was modified to strike the language; “Where required by the fire code

official, address identification shall be provided in additional approved locations to facilitate emergency response.”

Section: R404.1.9.2 Masonry piers supporting floor girders. The section was modified to read that piers supporting interior bearing walls shall have a minimum dimension of 8 inches and a maximum height of 10 times its nominal thickness. Piers supporting exterior bearing walls shall have a minimum nominal dimension of 8 inches and a maximum height of 4 times the nominal thickness. All piers shall be grouted with Type M or S mortar and exterior piers shall have a #4 vertical bar.

Section R502.10 Framing of Floor Openings. Requirements for header joist and trimmer connections have been deleted as it conflicted with Section R502.6 which stipulates minimum bearing lengths. Now R502.10 stipulates that trimmers and headers less than 4 feet can be a single joist and over 4 feet must be a double joist.

Section R602.7(1)(2) Girder and Header Span Table. The Girder and header span tables have been changed to reflect #2 lumber as opposed to #1 plus reductions in the stresses. Some header spans have been reduced by 6-14”. Also note headers in pony walls now have a 30% reduction in span.

Section 802 Roof Framing. Changes to this section include;

Design and construction shall provide continuous ties across the structure to prevent thrust against supporting walls

Where continuous ties are not present a ridge beam must be used

Rafter spans are calculated along the horizontal

Ridge straps are allowed in place of collar ties

Collar ties shall be located in the upper third of the roof, ceiling joists shell be located in the lower third

Section R905.2.8.5 Drip Edge. A drip edge shall be provided at eaves and rakes edges of asphalt shingle roofs where required by the manufacturer.