Ice and Water Shield & Sheathing Requirements
The City of Buffalo, Wyoming has adopted the 2018 IRC and follows the code requirements for roof assemblies as outlined in Chapter 9.
R-905.2.7.1: In areas where there has been a history of ice forming along the eaves causing a backup of water as designated in Table R301.2(1), an ice barrier that consists of at least two layers of underlayment cemented together or of a self-adhering polymer modified bitumen sheet, shall be used in lieu of normal underlayment and extend from the lowest edges of all roof surfaces to a point at least 24 inches inside the exterior wall line of the building. The City of Buffalo also requires ice and water shield to be installed in all valleys and in transitions from one pitch to another.
905-.2.1: Asphalt shingles shall be fastened to solidly sheathed decks.
(Any gaps in sheathing exceeding 1/8 inch will require new sheathing installation)