This section talks about roof systems and how to prevent water from getting inside. The pitch of the roof structure determines the type of roofing and it is a water resistant covering for the roofing material, like overlapping or interlocking shingles and tiles. Flashing also prevents water from getting into the roof and it should be installed on the edges of the roof. Exterior walls also have to be flashed around the bottom of the door and window openings. Water vapor is the type of moisture that gets into the interior spaces of a building and when it reaches a surface that is cooled, condensation happens.