Oregon Construction Contractors (CCB) Practice Test

What construction feature must window sills include?

1. Weather stripping

2. Pan flashing draining to the exterior

3. Pan flashing that drains to the interior

4. Additional insulation

The correct answer is: Pan flashing that drains to the interior

The necessity of window sills in construction is primarily centered around effective drainage and the protection of interior spaces from water infiltration. The correct answer highlights the importance of pan flashing that drains to the interior. This design feature ensures that any water that runs down the window and onto the sill is properly collected and directed away from vulnerable areas. The inclusion of pan flashing that drains to the interior serves to channel water away from the window, preventing it from pooling or infiltrating the interior wall assembly. A well-designed window sill with this feature significantly reduces the risk of moisture-related damage, such as mold growth or deterioration of building materials, thus enhancing both the durability and functionality of the window. By contrast, other options such as weather stripping or insulation, while important for thermal and air sealing, do not directly address the critical drainage function that window sills must serve. Furthermore, pan flashing that drains to the exterior could create potential issues by allowing water to pool against the exterior wall, risking infiltration instead of proper drainage. Therefore, pan flashing designed to drain to the interior is essential for maintaining a dry, safe, and energy-efficient building.