Are shadow areas allowed within sprinkler protection zones?

Are shadow areas allowed within sprinkler protection zones?

• A. No, shadow areas are not allowed.
• B. Shadow areas must be completely wet.
• C. Shadow areas are allowed as dry areas within protection zones.
• D. Shadow areas must be protected by a separate sprinkler.

Answer: (C)

Shadow areas are spaces inside a sprinkler protection zone where direct spray from the heads can be blocked by obstructions. In NFPA 13R for low-rise residential buildings, these shadow regions can be treated as dry areas within the protection zone. That means the pipes in those spots aren’t kept water-filled under normal conditions, which helps prevent unnecessary water exposure in unheated or sensitive spaces, yet they remain protected because when a sprinkler is activated, water will reach the area as part of the ongoing protection pattern. This approach balances practical coverage with cost and risk in typical residential layouts. The idea is not that every shadow must be fully wetted on a permanent basis or that each shadow requires a separate sprinkler, but rather that within a protection zone, some shadow areas can be dry while the rest of the zone remains protected.