The 2018 International Residential Code (IRC) adopted by the City of North Richland Hills requires roof structural panel sheathing (OSB and plywood) to meet Table R503.2.1.1(1) and typically requires a minimum of 7/16 inch thick sheathing. Table R803.1 is used for solid lumber sheathing (such as 1 X 8’s) and requires a minimum of 5/8 inch decking where rafters are spaced 24 inches on center. Additionally, section R905 of the IRC requires asphalt shingles to be applied in accordance with the applicable provisions of the code AND the manufacturers installation instructions (which ever is the most stringent).
Please know that the city does not require citizens to replace 3/8 inch plywood roof panels if it is still in good condition; and presumes that the panels met the code at the time it was originally installed. In fact, the IRC still allows appropriately rated 3/8 inch roofing panels on rafters spaced 24 inches on center to this very day; however, this product has been difficult to locate. Please be advised that there are occasions where the shingle manufacturer’s installation instructions are more restrictive than the IRC by mandating that their shingles be installed on 7/16 inch or thicker roof panels in order to honor their product’s warranty.
For additional information, please see the Owens-Corning Technical Bulletin for roof decking requirements at http://www.owenscorning.com/NetworkShare/Roofing/10022499-Roof-Deck-Requirements-Technical-Bulletin---TB-07.pdf