A.William Rose, a research architect with the Building Research Council at the University of Illinois at Urbana-Champaign and the author of Water in Buildings: An Architect's Guide to Moisture and Mold, responds: If there's a cavity in the wall, it should always be designed to manage rainwater. That's because a CMU veneer — such as brick — allows some rainwater to enter the wall, travel along mortar droppings, and create local wetting of the block.

But saying the block wall should be "dampproofed" only begins to address the serious task of detailing the cavity water-management layer; coordinating it with insulation, ties, flashing, openings, and protrusions; and possibly having it serve as the air-barrier layer.

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