The outermost reinforced layer of the roof assembly. In BUR it’s the multiple-ply membrane, in Thermoplastic roof systems it’s the thermoplastic sheet, etc.

The exposed exterior roof skin consisting of panels or sheets.

The exterior roof skin consisting of panels or sheets, their attachments, and weather sealant.

(1) The exterior roof cover or skin of the roof assembly, consisting of membrane, panels, sheets, shingles, tiles, etc.; (2) The covering applied to the roof deck for weather resistance, fire classification or appearance.

Shingles, tiles, etc., that protect the decking from weather. This is the first layer of protection for your roof decking.

The exposed exterior roof surface consisting of panels.