Mold Growth On Basement Woodwork

This video is showing mold growth and staining in a split level basement ledge of the exterior wall.  The basement was finished off about a year ago, with the mold and staining starting within the last two months. The owner pointed out this problem during the home inspection and asked me if I could help to figure out the cause. This wall was the only one in the basement that had this problem. All other areas were dry at the time of the home inspection.

What I had found was on the exterior of the home, the bottom of the siding was right at the top of the block/base plate junction. With all of the rain and driving winds we had had recently, I believe that water was being driven into the joint at the top of the wall, resulting in saturation of the wood. The water was wicking up through the oak shelf, which was attached to the base plate,  thus causing the staining and mold growth.

For some reason, the siding on this side of the home was not installed low enough to properly overlap the masonry block/plate joint. The siding was installed properly on the remaining exterior walls.

My recommendation to the homeowner was to have a siding contractor extend the siding down so that it properly overlapped the masonry block. I also recommended that the oak shelf be removed, the area inspected for moisture issues, necessary repairs be made.