Slope? Sheathing? Rafters? What are they talking about? They’re talking about roofs right? In this post we share some common roof terms and parts to help you have an understanding of how your roof is built. A well-built roof seals out water and directs it to gutters and downpipes, which carry away from the house. To perform at its best, the underlayment, flashings and the rowing material should be installed properly so that water can’t get in under and damage the sheathing.