What does primary drainage handle?

• A. Normal rainfall but may clog due to debris or maintenance failure.
• B. Heavy rainfall events only.
• C. Snow and ice accumulation.
• D. Drainage under heavy groundwater infiltration.

Answer: (A)

Primary drainage is the system that removes the roof’s normal rainwater runoff so the surface doesn’t pond. It relies on gutters, downspouts, and roof drains sized for typical rain events. It can be compromised if debris builds up or maintenance is neglected, which reduces flow and can cause ponding even in ordinary rain. In very heavy rain, the primary path can be overwhelmed, requiring secondary drainage or overflow paths to carry excess water. Snow and ice bring different drainage challenges due to freezing and meltwater behavior, and heavy groundwater infiltration isn’t handled by roof drainage—that involves subsurface conditions and waterproofing concerns.