Split face block (SFB) is a concrete masonry unit (CMU) that was the
rage in condo and home construction in Chicagoland from the early
1990s until the housing bubble burst in 2007. Thousands of these
properties were built with face brick at the front, and SFB on the sides
and at the back of the structure. Most of these buildings are now
experiencing water infiltration through the walls.

http://www.inspection2020.com/SFB.pdf