Choosing the Right Metal for Masonry Flashing

Let's start with the BIA (Brick Industry Association) Technical Note 7A's recommendation listed below:

Mill-Galvanized Steel

Galvanized flashing is available, but the coating is not hot-dipped, resulting in a thinner protective layer. Bending galvanized sheets to create flashing shapes will crack the coating and compromise the corrosion protection. In addition, the coating is sacrificial compared to the inert finishes of other metal flashings, which result in reduced service life and durability. Therefore, use of galvanized steel as through-wall flashing is not recommended.

Aluminum

Aluminum should not be used as a flashing material in brick masonry. The caustic alkalis in fresh, unhardened mortar will attack aluminum, although, dr, seasoned mortar will not affect aluminum, corrosion can occur if the adjacent mortar becomes wet. Anodized or organic coatings can provide some protection against this condition but are still not recommended for flashing, as they will not provide the same performance as an inert material for embedded elements. These coatings should provide adequate protection of exposed aluminum elements within the wall system, such as window frames, from precipitation runoff.

When asked the question, “Is there a preference for aluminum flashing vs. galvanized steel flashing in masonry construction if stainless steel is not within budget?” what is the correct response?

In masonry construction, the only choices for sheet metal pan flashings are stainless steel or copper. Value engineering the pan flashing to metals that will not pass the test of time is not the only choice. Using a flexible stainless steel flashing with a stainless steel drip edge will be dramatically less than a stainless steel pan and have a similar life expectancy.

This option is a cost and labor-savings and helps you avoid corrosion issues compared to using a galvanized or aluminum flashing.

To the right is an example of a galvanized steel detail and a picture of the constructed wall. The failure of the flashing occurred before the construction of the job was completed.

Detail calls out galvanized steel as the through-wall-flashing. When installed this way the flashing will rust and fail.

Example of a rusted drip edge that has failed

Example of a Type 304 stainless steel drip edge