Question: what are the layers on a roof?
Answer: Decking. The roof deck is the roof layer (also called sheathing) that is installed between the trusses & joists and underlayment layer in a typical roof install. ... 
Starter Strip. Starter strip shingles are a strip of shingles that line every edge of your houses roof. ... 
Underlayment. ... 
Shingles. ... 
Ridge Caps.