There Is More Under a Door Than the Threshold
Exterior doors interrupt the wall’s water-management system.
If water reaches the bottom of that opening, it needs a path back outside.
That is the purpose of:
Sill-pan flashing.
What Is It?
A sill pan creates a water-resistant layer beneath the door or window opening.
It may be:
- Flexible flashing
- Rigid pan
- Fluid-applied system
Building Science guidance recommends sill flashing that directs water outward rather than allowing it into the wall cavity.
Why Does the Back Edge Matter?
Some sill-pan designs include a back dam.
That helps prevent incidental water from moving toward the interior.
Does Exterior Caulk Replace It?
No.
Sealant is useful, but water management should not depend on one exposed bead remaining perfect forever.
Proper flashing provides drainage behind the visible finish.
Why Is This Important in Wind-Driven Rain?
Strong rain can push water into small exterior gaps.
A correctly detailed opening provides a secondary path back outside.
A Good Door Installation Plans for Water You Don’t See—not Just Rain You Do See.
Envirotech Exteriors considers sill flashing, threshold, frame, weatherstripping, and exterior trim as one entry system.