Counter Flashing Material Options: Pros and Cons
While one can safely assume that building materials such as brick, stone, and vinyl provide protection against water seepage that can fatally damage exterior and interior wood structures, another precaution that extends the life of wood structures is flashing. Flashing, a stripping usually formed from metal, is utilized oftentimes at joints or seam points where a crease occurs or where two objects intersect, such as a vent pipe protruding from a roof, in order to divert water away from the weak spot or opening. In the case of brick walls and in particular brick chimneys, counter flashing, using two pieces of flashing wherein one piece overlaps the other to bolster sealing, is introduced.
When attached to brick walls or brick chimneys, counter flashing’s role is to force water downwards to a roof, gutter, or other surface below. This entails that the flashing material come into constant contact with wind, precipitation, or fallen objects and debris that collect. Due to its position, the material to be used as flashing must be considered as such materials are not completely impervious to weathering as well. Three common metals formed into counter flashing are aluminum, copper, and galvanized steel. Though all three have value, each must be evaluated by their respective positives and negatives by homeowners and contractors.
The most commonly used material for counter flashing is aluminum. Aluminum holds a great deal of value for multiple reasons. First, aluminum, when taken care of, has a long life expectancy—upwards of 20 or more years. Next, the metal can be custom fitted and pieces easily slide together. Third, as it is often painted, which produces a nice weatherproofing layer, it can be relatively corrosion resistant. Finally, and most important for many homeowners, aluminum is the least expensive material. However, with these benefits come some detractions. While aluminum is highly rust-resistant, if improperly cared for or if damaged and neglected, oxidation or corrosion may occur from unpainted aluminum being in direct contact with mortar, and rust can ensue. As aluminum is lightweight and often thin, it is weaker and more easily damaged by fallen limbs or ladders placed against it. Another issue is that the material cannot be soldered. Although the pieces can be placed together easily, the joints can be weaker even when nailed together.
(Aluminum Chimney Counter Flashing, top, and Galvanized Steel Soldered Chimney Counter Flashing, left)
Galvanized steel is a second metal used for counter flashing. Steel blends strength and durability, especially when galvanized. When protected and properly maintained, galvanized steel has a life expectancy of around 40 years. The galvanization process results in rust resistance, extending its life. Adding to its strength, the joints between steel pieces can be soldered, thus creating in essence a single unit. The negatives for galvanized steel include a propensity to rust if not maintained. Worse, rust formations eventually lead to small holes in the metal, which then leads to water intrusion. Noticing a deterioration of the galvanized layer is not simple, which can make maintaining or repairing weak areas difficult. Another con is that the material is heavy. While the thickness and weight make steel strong, those same attributes make it unwieldy and tough to custom fit and install.
A third metal that can be used is copper. Copper is extremely durable, often lasting for decades. It is the most aesthetically beautiful of the metals, both in its early years when a burnished brown and when the green oxidation patina often sets in. Like galvanized steel, the joints can be soldered to create a strong piece, but unlike steel, copper is light and exceedingly malleable. These features make it easy to shape, mold, and install. While likely the best choice for flashing, copper is also the costliest of the three metals. The value placed on the metal also makes it a target for thievery, so homeowners with copper flashing or gutters must be vigilant. Another problem, like aluminum, is that copper can be damaged by fallen limbs or ladders.
Counter flashing delivers an indisputable protection for roofs and walls. With various options available, homeowners and builders should consider cost, durability, maintenance, and strength of materials before making a choice. The life of the home and the bank accounts of owners often depend heavily on such details and decisions.