Incomplete Wrapping

All too often I see sloppy and incomplete housewrap installations; the housewrap is installed any which way, with no attention to proper layering.

Gable ends.

For some 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 housewrap. 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 joist below.

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.