One California engineer's observations over the past 16 years.......
The vast majority of CMU construction for buildings is solid grouted. I do
recall seeing hollow cells in a CMU fence after it was hit by a car. I've
never even seen a piece of ladder reinforcing except in pictures.
Bill Allen's rationale for partialy grouting walls laterally supported by a
wood diaphragm makes a lot of sense. My design experience is concentrated in
total concrete and masonry structures using wood only as formwork.
I think solid grouted construction with rebar in both directions accounts
for +90% of the CMU work for buildings out here.
Brent R. Koch, P.E.