Sheathing

Sheathing is defined as the layer of boards or panels (plywood or OSB) fastened to the roof rafters or trusses to form the structural roof deck. The terms sheathing and decking are used interchangeably in residential roofing. Standard sheathing panels are 4 feet by 8 feet and are installed with a 1/8-inch gap between panels to allow for thermal expansion. All sheathing must meet APA (Engineered Wood Association) performance standards and be rated for the specific rafter spacing and load requirements of the roof.