When it comes to waterproofing, the devil is in the details. That’s why it’s important to know which materials to use – and where, and WHY. One old colloquialism is to “think like a raindrop” to help visualize water flow and eliminate intrusion into the building before it happens. Whether you’re in California or Washington, or anywhere else, you have to consider how your building deals with water.

One place that is especially prone to water intrusion is any place that a vertical plane meets a horizontal one. At the bottom of a wall, for example, or the point where a siding board meets a trim board, there ALWAYS must be a metal Z flashing that projects a minimum of 1/8″ past the horizontal plane edge. There must also be a 35° angle between the main vertical flashing leaf and the horizontal leaf, to improve runoff.

NEVER EVER caulk the top or bottom of flashing. This impedes water flow and causes pooling behind the finished surface. Run your flashing as described, and you can even add details like end bends on the left and right ends to point straight up and shoot water straight out. Remember to install the flashing before the finished wall, and install it running up underneath the Weather Resistive Barrier, leaving a 1/4″ gap to reduce wicking or capillary draw.

And that’s it! Merry weatherproofing. If you need a hand, give us a call we’d be happy to help with our years of expertise.