The core idea
Brick veneer and cavity walls need clear drainage routes at the base and above openings.
How the mechanism works
Water passing through masonry falls within the cavity and exits through flashings and weeps.
When it becomes relevant
Typical trigger: Wind-driven rain or blocked drainage paths.
Evidence that supports this interpretation
- Symptoms appear above or below openings
- Weeps are absent or blocked
- Mortar droppings may bridge the cavity
Evidence that weakens it
- The wall is solid masonry without a cavity
- A roof leak enters above
- The mark follows indoor humidity
What this concept cannot prove alone
A single observation, image or meter reading cannot confirm the complete failure pathway. Use this concept to form better questions, compare alternatives and decide which safe observation would be most informative next.
Safety and professional boundary
Cavity opening and masonry repair should preserve structural ties and flashing continuity.
Primary references for this topic family
These references ground the general building-science or safety context. They do not diagnose a specific house, replace local requirements or certify a repair.
US Department of Energy · government homeowner guidanceConsumer Guide to Air Sealing the HomeAir leakage, durability, comfort and ventilation coordination.Verified 2026-07-20 · review due 2027-01-20Open source ↗US Environmental Protection Agency · government guidanceMoisture Control Guidance for Building Design, Construction and MaintenanceMoisture sources, transport, design, construction and maintenance controls.Verified 2026-07-20 · review due 2027-01-20Open source ↗US Department of Energy · government research libraryBuilding America Publications and Solution CenterBuilding enclosure, HVAC, windows, indoor air and high-performance housing research.Verified 2026-07-20 · review due 2027-01-20Open source ↗
Observe→Compare triggers→Repair source→Verify outcome
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