The base of wall is one of the most vulnerable locations for moisture accumulation. This article explains how to properly detail base flashing, through-wall flashings, and weep mechanisms for long-term durability and moisture control.
Moisture Management Principles
All cavity wall and rainscreen systems should include a drainage plane and exit path at the base. Through-wall flashings must extend beyond the outer cladding and direct water away from sheathing, framing, and insulation. Weeps provide the escape route for moisture exiting the wall cavity.
Flashing Installation Best Practices
- Install through-wall flashing at or just above grade, sloped to shed water
- Extend flashing a minimum of 1 inch beyond face of veneer or cladding
- Seal flashing into vertical WRB using tape or liquid flashing membrane
- Lap WRB and air barrier layers over the upturned leg of flashing
Weep Detailing
Install weeps every 24–32 inches horizontally and at each opening or transition. Use plastic weep vents, cotton ropes, or proprietary mesh weep devices that maintain open drainage while deterring insects. Avoid blocking weep paths with mortar droppings—use cavity screens or mortar nets behind flashing to preserve clear drainage.
Inspection and Field Quality Control
Verify proper slope of flashing before cladding installation. Conduct water spray testing to confirm drainage through weeps. Check that all edges are sealed to adjacent materials, and that no weeps are obstructed. Document flashing placement with photographs during open cavity inspection for code and warranty compliance.
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