TL;DR
A back dam is the raised interior edge of a window or door sill pan flashing that stops wind-driven water from running off the back of the pan into the wall or floor below. Best-practice flashing details and standards like ASTM E2112 call for one at least 1/4 to 1/2 inch tall, formed in bent metal, rigid pan products, or a sloped wood strip under flexible membrane.
What it means
A back dam is the raised interior edge of a window or door sill pan flashing that stops wind-driven water from running off the back of the pan into the wall or floor below. Best-practice flashing details and standards like ASTM E2112 call for one at least 1/4 to 1/2 inch tall, formed in bent metal, rigid pan products, or a sloped wood strip under flexible membrane. It works with the pan's sloped bottom and open front, which drain leaks outward instead of trapping them. Rot at the corners of door openings is the classic symptom of a sill pan installed without one.
Where it sits in the glossary
Back dam is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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