Reverse laps happen when trades install out of sequence, when a window is set before the wrap below it, or when a patch is tucked under instead of over. Water running down the face meets an edge that opens upward and goes straight in. Tape cannot reliably fix a reverse lap; the layers usually have to be cut and redone in the right order.
Wrap's reverse lapped at the head, it's tucked under the window flange, so every drop running down the wall goes behind the flange.
Also heard as
- reverse-lapped
- wrong-way lap
Related terms
Shingle lap
Overlapping layers so each upper piece lies over the one below, sending water down and out like roof shingles.
WRB
Water-resistive barrier, the layer behind cladding that sheds water that gets past the outer skin.
Sill pan
A tray of flashing under a window or door with a raised back and ends, catching any water that gets past the unit.
Strip-in
To seal the flange of a flashing or fixture to the surrounding membrane with an overlapping strip of tape or sheet.