Siding is put on a house primarily to keep water from entering the building through the walls. In order to perform this duty, correct detailing and installation are critical.

In this photo, a new layer of vinyl siding was installed on top of the existing siding. Note, however, how the "J" bead at the top is simply attached to the wall with no protection. Typically the top of the siding would be protected by a roof overhang or soffit. On this particular house, however, there is no soffit to prevent water from slipping in behind the new siding. Note also that the corner is completely exposed at the top, basically acting as a funnel.

The remedy for this would be to install sheet metal flashing on the fascia board to direct water out and over the siding instead of behind it.

Remember the "Rule of Two": Good, fast and cheap - pick two. This siding installation was fast and cheap, but not a good long term choice.