Chimney counter flashing

Installing a counter flashing against a chimney isĀ  task that will prevent any water from infiltrating into your home through the roof. Counter flashing will also increase the lifespan of your chimney masonry.

Materials and tools

  • 4 inch grinder with masonry blade
  • Extension cord
  • Safety glasses
  • Gloves

Mortar joint

To install a counter flashing, you must form what is known as a reglet.

This task involves removing the mortar join from around the step flashing. You must make sure that the water will drain away from the chimney as it should. To do so, cut a 1 inch deep slot into the mortar joint being careful to follow the step flashing line.

Counter flashing

Installing the counter flashing is simple. You just have to place it in the slot where the mortar joint has been removed and carefully bend it over the step flashing. Never use aluminum for counter flashing. It is best you use stainless steel metal or copper.

Finishing touch

To cover the step flashing properly, the counter flashing should be at least 4 inches wide.

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