Flashing for Concrete Block Walls


Flashing is one of many types of waterproofing used in home and commercial construction. At their basic level, they are thin pieces of waterproof material installed to ensure that water doesn’t penetrate at joints. With concrete block walls, there are several areas where flashing needs to be installed to protect the home from water penetration over the years.

Outside Corners

  • While not all outside corners need to have flashing installed, you can purchase optional pieces to put on top of the block. These usually depend on the type of finish material you are installing, such as brick veneers or vinyl siding. The outer corner flashing not only helps hold the finish material in place but also acts as a protective barrier against weathering plus water damage from the exposed outer edge.

Inside Corners

  • Inside corners will almost always require some type of flashing that is caulked in place or somehow otherwise covered by waterproofing elements, such as a paint-on waterproofing that not only covers the surface of the block but also the corner. They can be stand-alone flashing strips or they can be part of an overall waterproofing protocol, such as a membrane system that has its own flashing to go with the membrane.

Window Wraps

  • All windows need flashing installed around the edge of the window frame. Windows are one of the most prone areas of a home for water to penetrate and leak, and if a window is installed without flashing you can guarantee that it will leak the first time a rain puts water on the exterior of your home. The options you can choose from are varied, from metal to plastic and vinyl, but they all serve the same purpose by forcing water away from the window and down the face of the wall.


  • Although guttering is installed on most homes as a way of protecting the eaves of a house from the runoff that is a result of the roof slope, flashing at the eaves is also important. This flashing helps any excess water from the roof runoff to funnel down and away from the wall via the flashing, rather than running down and under the siding or other finish material installed on the face of the block.

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