Significant 2018 IRC Changes

After a few years of somewhat sedate changes in the residential code, 2018 has ushered in a few changes that need to be kept in mind. A link to the latest version of the 2018 IRC with South Carolina Amendments can be found at Upcodes. Below are a few of the items that have changed and are worth reviewing.


+ ATTIC, HABITABLE - A finished or unfinished habitable space within an attic

+CRAWL SPACE - An underfloor space that is not a basement.


+Appendix H Patio Covers

+Appendix J Existing Buildings

+Appendix Q Tiny Houses


+Section R301.2 now requires the local jurisdiction to establish Manual J design Criteria

+Section R302.2 Towhouses - reorganized the section & added R302.2.1, which expressly requires each townhouse shall be separated by two 1-hour fire-resistance-rated wall

+Section 308.4.4.1 Structural Glass Baluster Panels - This sub-section was added to bring clarity of the required application of glass baluster panels and the requirements for top rails.

+Section R308.4.2.2 Glazing Adjacent to Doors - was adjusted to clarify for conditions where the adjacent wall was not perpendicular to the plane of the door.

+Section R310.1 added an exception for Emergency Escap requirements if the residence is sprinkled.

+Section R311.7.3 added 4 inches to the allowable vertical rice of stairs between landings, from 147 inches to 151 inches.

+Section R311.7.8.2 Handrail Projection was added, defining the maximum handrail projection to 4 1/2 inches.

+Section R314.4 Interconnection of Smoke Alarms, removed the prior exception for alterations or repairs. Interconnected smoke alarms are now required when a residence is altered or repaired.

+Section R325.6 Habitable Attic, was added to clarify that a "finished attic" in NOT considered a "story."

+Section R322.1 Flood Resistant Construction, added the text "Where there is a conflict with this code and a locally adopted flood ordinance, the more restrictive shall apply" to permit local jurisdiction to enforce more stringent codes if they so choose.

+Section R408.3 Unvented Floor Space, added subsection R408. to provide a minimum amount of dehumidification for "conditioned crawl spaces."

+Section R507 Exterior Decks, has been completely reorganized. The section now begins with permitted materials, progressing through footings, posts, beams, joists, and decking. This presents a more logical order than the prior years, which started with decking and ended with posts/footings.

+Section R602.3.1 Stud size, height and spacing, has added Table R602.3(6), which provides for prescriptive stud sizing and spacing for heights up to 12 feet. The prior editions of the code only permitted prescriptive stud heights to 10 feet.

+Section R602.7 Headers, updated the tables to reflect using the more common #2 SYP instead of #1 SYP as headers.

+Table R703.8.4(1) covering Brick Masonry Veneer attachment has added Note C,"An airspace that provides drainage shall be permitted to contain mortar from construction."

+Section R802 Wood Roof Framing, was substantially reorganized in a more logical layout. The new organization places emphasis on Continuous Ties, removes tables for the 5 PSF dead load, and clarifies purlin braces.

+Section R802.2 Minimum Roof Ventilation Area, Exception 2 was adjusted to permit alternate vents in the lower third of the attic.