Question for those familiar with retaining walls and fences. I have someone who needs to have a new fence installed. Because the property next door is a rental/foreclosure property, she wants some added fence height as well as barrier for trash and debris from coming onto her side. On her side she plans to install a raised flowerbed.

The current mode of thinking is to run a footing and 2 block high cinder block retaining wall with steel fence posts set into the solid filled blocks with a 6' wood fence on top of it.

The question is, how deep and wide must the footing be to support the two rows of block and a 6' solid wood fence? My concern is wind shear resistance, not weight or settling of the block. We do not have frost here, so that is not a factor. Soil is rock hard clay in the summer. In the winter, only the top few inches get a little mushy, and it's only those areas that have been amended to any degree.

Another reason for the footing and retaining wall is to keep whatever garbage the neighbor plants or lets grow from rooting over into my friends property, as all of the scrub trees and shrubs do now.