The layered weather boundary formed by roof covering, underlay, flashings, penetrations and drainage.
What this system controls
A symptom rarely belongs to one component in isolation. This system page connects visible signs, likely failure modes, useful checks and the parts that should be examined together.
How to investigate it
Start with timing and location, then compare weather, occupancy and equipment cycles. Document what changes before opening finishes or replacing parts.
Repair sequence
Confirm the source, control immediate damage, repair the cause, restore affected layers and verify the result under the condition that originally triggered the symptom.
Observe→Distinguish→Control source→Verify
Living dossierPublished knowledge is connected and improved as new cases, images and outcomes are added. Updated 2026-07-20.
