US Patent 7526900 Masonry cavity wall having a compressible, expandable debris blocker

A mortar and debris collection device for use within a cavity wall to prevent the blockage of weep holes at the base of the wall. The cavity wall assembly includes a masonry wall, an adjacent inner wall, a wall cavity therebetween, and a free-standing elongate strip of openwork material located within the cavity forming a debris collection surface a spaced distance above a base surface of the cavity. Preferably, the openwork material is inserted and positioned within the cavity after the inner wall and only a base portion of the outer masonry wall is constructed. Thereafter, the upper portion of the outer masonry wall is constructed and any mortar or debris falling into the cavity is caught and supported on the debris collection surface.