In working on an addition to a 15-year-old building, we removed a large section of brick veneer over metal studs. We noticed that the outer faces of the studs were significantly corroded where they contacted the sheathing. Other parts of the studs were mostly free of corrosion. Why is this occurring?
There are two likely causes for corrosion in this location. Water may be leaking into the stud space either by bridging across the cavity or coming in along the top of the stud wall. This water will saturate the sheathing and hold water against the steel. The second cause of this problem may be condensation. Water will condense on any surface that is at or below the dew point temperature. The location of the dew point in walls will vary depending on the time of year and the building's geographic location. Corrosion of the outer stud flanges can become very serious, greatly reducing the structural capacity of the studs. It also will reduce or eliminate the holding power of screws into the studs. If the outer flanges are significantly corroded, the screws used to attach the ties to the studs probably are, too. I recommend investigating to determine the source of the moisture and to evaluate the condition of studs in other areas.