Technical library
RCI Interface “Roof Leakage Deception – Exterior Walls May be the Culprit”
Ceiling stains at the perimeter often get blamed on the roof. See how parapets, copings and wall details mimic roof leaks — and how testing tells them apart.
Article by Pamela Jergenson, CCS, CCCA
Read the full article (PDF)Common questions
How can I tell whether a leak is coming from the roof or the wall?
Track the conditions. Leaks that appear only with wind-driven rain from one direction, during a thaw with no rain, or several hours after a storm point toward the wall. Steady leaking during any sustained rainfall, especially away from the perimeter, points toward the roof. Controlled water testing confirms which assembly is actually admitting water.
Why do parapet walls cause leaks that look like roof leaks?
A parapet sits above the roof and is exposed on both faces. Water entering through open coping joints, cracked mortar or failed sealant travels down inside the parapet and reaches the deck behind the base flashing. The stain then appears at the interior perimeter, directly under roofing, even though the roof membrane is sound.
Should the roof be replaced if repairs have not stopped a perimeter leak?
Not before the source is confirmed. Repeated unsuccessful roof repairs are evidence that the entry point may be elsewhere in the enclosure. An investigation that includes the parapet, through-wall flashing, cladding and window perimeters can prevent an owner from buying a roof that was never the cause of the problem.
Does Inspec perform the repair work once the source is found?
No. Inspec is a consulting engineering and architecture firm. We investigate and test to identify the source, document the findings, and can prepare repair documents and observe the contractor's work during construction. The repairs themselves are performed by contractors, which keeps our assessment of the work independent.