Are Holes Necessary in a Foundation Weep Screed?

(Re-Submitted from 4/10/10 Blog)- ASTM 1063-03, 6.3.2 states the following:

"This accessory (foundation weep screed) shall have a sloped, solid or perforated, ground or screed flange to facilitate the removal of moisture..."

According to the ASTM listed above, a Foundation Weep Screed may or may not have holes. What it does require is a sloped edge for the evacuation of moisture that may reach the water resistive barrier. One must keep in mind that during the curing process, cement plaster will shrink away from the sloped flange of the weep screed approximately 1/32 of an inch. This space is sufficient to create a passage for moisture to escape.

Contrary to popular belief, holes in Foundation Weep Screeds are not "weep" holes. The holes are typically plugged solid with stucco. In fact, the holes in weep screeds could inhibit weeping since moisture could pool above these plugged up holes. If moisture does find its way through the perforations on the screed flange, it may be directed back towards the foundation where the weep screed's lower flange rests against it.