BSC investigated a house under construction in a coastal Massachusetts location; although dry-in and cladding had been completed, rainstorms consistently resulted in water leakage to the interior, with visible pooling on the floor. BSC was asked to determine the source of these water issues, and provide recommendations for addressing this leakage before building interior completion.
BSC systematically examined leakage patterns, using infrared thermography and wood moisture content measurements. The areas below window sills (especially at corners) had moisture measurements higher than the field of the wall, and in some cases, visible water was found. The visible active leakage was traced from a second floor window, draining to the first floor.
This was followed by an examination of window and other flashing details, and spray rack testing of windows with building depressurization (to simulate wind). Water spray testing replicated suspected the window leakage issues.
The reason for the water leakage issues was the lack of a window sill pan flashing; water that entered imperfections at the window-wall interface (given the extreme climate loading) bypassed the water control layer (housewrap), and ran inside.
BSC provided a range of remediation recommendations, including (a) only removing and reinstalling the windows with a sill pan flashing detail, or (b) removing all exterior cladding, to upgrade the water control membrane/drainage plane, and add a drainage gap material for a further upgrade in performance. The owners elected to take the latter (more intrusive) option, using a liquid-applied vapor-permeable water control membrane on the sheathing surface.