Roof system

All steep-slope roof systems (i.e., roofs with slopes of 25 percent or more) have five basic components:

Roof covering: shingles, tile, slate or metal and underlayment that protect the sheathing from weather.

Sheathing: boards or sheet material that are fastened to roof rafters to cover a house or building.

Roof structure: rafters and trusses constructed to support the sheathing.

Flashing: sheet metal or other material installed into a roof system's various joints and valleys to prevent water seepage.

Drainage: a roof system's design features, such as shape, slope and layout that affect its ability to shed water.