All too often I see sloppy and incomplete housewrap
installations; the housewrap is installed any which way, with
no attention to proper layering.
reason, builders often think they can get away without wrapping
the gable ends (photos A & B). This may be because they're
thinking of the wrap only as an air infiltration barrier but
not as a weather barrier, and figure there's no reason to worry
about air leaking into the attic.
This is a mistake, because the gable is one of the most
exposed parts of the house. Driving rain gets behind the
siding, runs down the sheathing, and winds up behind the
The problem often appears as drips along the top extension
jamb of windows or sliders below. It may be hard to diagnose,
because the leak may show up well below the point where the
water runs behind the housewrap.
Band joist. Another
problem area is the band joist. Walls may be sheathed and
wrapped while they're lying on the deck. Then, when the wall is
lifted, the band or mud sill remains unprotected (C & D).
Splashback from below as well as water running down the
housewrap from above can cause severe wetting. If you install
wrap this way, make sure you go back and cover the band joist
with a strip of housewrap, tucking it under the wrap above.
Note that in photo D this would be difficult to do, because
hold-down straps were installed over the wrap above and band
Outside corners. Often
housewrap doesn't quite make it around the corners (E). Like
gables, corners get a lot of weather exposure, and any water
that enters at this intersection of trim and siding then has
direct access to the structure. A leak at this point may never
show up inside the house, but can nonetheless lead to rot over
time. Make sure your housewrap extends all the way around
corners. We typically add a layer of tarpaper over the
housewrap behind all corner trim boards.