2018 North Carolina Residential Code — Chapter 9 Roof Assembly Excerpts

2018 North Carolina Residential Code ADOPTS WITH AMENDMENTS: International Residential Code 2015 (IRC 2015) Chapter 9 Roof Assemblies Section R901 General R901.1 Scope The provisions of this chapter shall govern the design, materials, construction and quality of roof assemblies. R905.1.2 Ice Barriers In areas where the average daily temperature in January is 25°F (-4° C) or less or when Table R301.2(1) criteria so designates, an ice barrier shall be installed for asphalt shingles, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood shingles and wood shakes. The ice barrier shall consist of not fewer than two layers of underlayment cemented together, or a self-adhering polymer-modified bitumen sheet shall be used in place of normal underlayment and extend from the lowest edges of all roof surfaces to a point not less than 24 inches (610 mm) inside the exterior wall line of the building. On roofs with slope equal to or greater than 8 units vertical in 12 units horizontal, the ice barrier shall also be applied not less than 36 inches (914 mm) measured along the roof slope from the eave edge of the building. Exception: Detached accessory structures not containing conditioned floor area. R908.3 Roof Replacement UpCodes note: The 2017-2021 Approved Amendments 201309-Residential Code has an update to this section. Roof replacement shall include the removal of existing layers of roof coverings down to the roof deck and replacement of up to 15% of the total existing roof deck. Replacement of up to 15% of the total roof deck shall not be considered structural work. Exception: Where the existing roof assembly includes an ice barrier membrane that is adhered to the roof deck, the existing ice barrier membrane shall be permitted to remain in place and covered with an additional layer of ice barrier membrane in accordance with Section R905. The delayed effective date of this Rule is January 1, 2022. The Statutory authority for Rule-making is G. S. 143-136; 143-138. Decking Requirements The code for asphalt shingles, and specifically their sheathing requirements, are found in section 905.2.1 of the 2012 IRC. It states “Asphalt shingles shall be fastened to solidly sheathed decks.” Deck sheathing is then discussed in section 803, specifically 803.2 under “wood structural panel sheathing”. Lumber sheathing (commonly referred to as plank decking), is found in a lot of older homes. It usually consists of a “1x” type material, such as a 1x4, 1x6, or even 1x12 material has been observed. The code asking for solidly sheathed decking then brings the question- “What is solidly sheathed?” The definition lies in how the decking is applied. Plywood, OSB, etc. (any APWA roof approved sheathing) is an obvious choice, but where do we go when we encounter the solid lumber sheathing, or planked decking? The code refers to the installation of this material, where most contractors reference the size of the gap between the lumber as the criteria for installation. The reason for the contractor asking is usually because the manufacturer of the asphalt shingles lists a “maximum gap” allowed in decking spacing, and anything larger then voids their warranty. The code does not consider the gap when asphalt shingles are applied, only wood shake, cement tile, and clay tile use the gap allowed parameter. The code leans towards the installation of the lumber decking as the method for rejection or acceptance. Basically, it requires a “ship-lap” or “tongue and groove” installation, otherwise, the decking needs to either be sheathed over, or the lumber decking removed and solid structural panel sheathing be applied. — Steep roof – above 4:12 slope – 29 CFR 1926.501(b)(11)