This section discusses roof systems and how to prevent water from going into a structure. In a roof system, they get a water resistant covering from roofing materials like overlapping or interlocking shingles and tiles. Flashing also helps prevent water from coming in. Flashing gets installed on the edges of the roof. The type of moisture that gets in is water vapor. Wall flashing collects any moisture that penetrate a wall. Rain penetration can be controlled by tooling mortar joints, sealing joints and sloping the horizontal surfaces of sills and copings. Cavity walls are also good in resisting water. Ching also talks about masonry veneer.