Siding is the first line of defense against water intrusion and the multitude of problems it causes including the dreaded mold.

But many builders fail to protect the most vulnerable areas of siding with proper flashing that directs moisture away from the building envelope. Today’s metal flashing even comes pre-finished to match the color of the siding for a professional, cohesive look that will protect the siding as well as builders’ reputations.

Here are four ways to use metal flashing to prolong the life of siding:

  1. Inside corner W flashing. When it comes to flashing siding corners, many builders simply use a 1x wood corner. But unlike fiber cement siding, wood is almost sure to rot. And when those corners start to decay, they become weak spots for water intrusion. A better way is using simple extruded aluminum inside corner W flashing that will prevent water intrusion — and last as long as fiber cement siding.
  2. Window/head flashing. Many times, builders fail to use proper flashing at the top of windows. Instead they rely on wood trim or the fiber cement itself. But this method creates an easy spot for water to enter the walls. Using metal window/head flashing directs the water away from the wall and eliminates that problem. The flashing can be used over window trim, band boards, panel intersections, and other vertical surfaces.
  3. J flashing on transitions. One of the most vulnerable areas for siding is transitions, whether it’s trim or an alternative siding. That’s especially true for the popular manufactured brick and stucco, which have a tendency to hold moisture. Using a metal J flashing between these types of transitions provides a barrier between siding and transitions that protects against water intrusion. But the J cap also creates a consistent line between the cut edges of siding and transitions so builders don’t have to worry about uneven edges or caulking and sealing joints.
  4. Metal coil flashing. Sometimes, preformed flashing just won’t fit. Rather than ignoring that situation, builders can turn to metal coil flashing that can be field formed into almost any shape. This low-maintenance flashing option is ideal for exterior trim surfaces such as window and door casings, windowsills, drip caps, fascias, porch posts, and louvers. And like other flashing, metal coil comes in most popular siding and soffit colors for easy matching and a professionally finished look.

For more on extruded aluminum flashing options go to