Q: I have seen projects where every third brick along the base of the wall is left out of the wall. I assume that this is done so the cavity can be inspected to make sure it is free of mortar droppings. These bricks can be installed after the rest of the wall's construction, and one weep can be put along one side of the brick. How effective is this approach? Is it necessary?
A: I have seen this procedure used on a few projects. Whereas it seems somewhat excessive, it does appear to work effectively. This procedure is one of the methods discussed in Brick Industry Association's Technical Note 7B, which states that by leaving out every third brick or so from the course above the flashing, the base of the cavity is accessible for cleaning. I once saw a masonry contractor place a large diameter rope in the base of the cavity, in addition to leaving every third brick out of the base of the wall. The masons threaded the rope into one opening and out of the other. They cleaned the cavity by removing droppings that collected on the rope when it was pulled from the opening.
Although this approach seemed to work, I have seen masonry contractors use other approaches to maintain clean cavities. Back-beveled bed joints, when properly done, can be very effective in avoiding mortar protrusions and mortar droppings. I prefer this approach primarily because it is an effort to keep the cavity clean in the first place, rather than removing mortar after it falls into the cavity.