Built-Up Installation of Layers

(1)  In hot process applications, each layer of bitumen-saturated felt shall be laid while the bitumen is hot, with each layer overlapping the previous one.

    (2)  The full width under each lap referred to in Sentence (1) shall be coated with bitumen so that in no place does felt touch felt.

    (3)  Felt shall be laid free of wrinkles and shall be rolled directly into the hot bitumen and broomed forward and outward from the centre to ensure complete adhesion.

Article Ontario Regulation 332/12 Building Code,   O. Reg. 332/12: BUILDING CODE (ontario.ca) © Queen’s Printer for Ontario, 2021

Built-up roof

Source : Canada Mortgage and Housing Corporation (CMHC)