Sorry if this is repetetively redundant by now--tried to send on Monday, but was having list issues. Have not seen other comments on "sounding" CMU walls to find un-grouted vs. grouted cells.
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Harold,
You can tell by "sounding" the wall which cells are grouted. Tap the wall with a hammer--the grouted cells sound very different than the ungrouted ones. Note: If you're not on site, this method doesn't help you much....
I inspected a CMU addition in Lompoc built in the 50s or 60s and it was only grouted where the reinforcing was.
One reason solid-grouting became common is that it's less labor-intensive than blocking off the cells below your horizontal reinforcement--plus you can do high-lift grouting instead of having to grout every horizontal rebar course before continuing to lay block. If you're using ready-mix trucks, you only bring them in once for grouting when the wall is topped out.
Best wishes,
Thor Matteson