Masonry Magazine October 2009 Page. 26
FLASHING & DRAINAGE
The geotextile-type weep devices are, by far, superior in design, as they absolutely are incapable of clogging when installed properly. They are also available in several different colors, giving options as to how they will look when sitting within the mortar joint. Unfortunately, where these fall short is the very design that makes them so effective. Tiny strands of polyester come together to form these miniature geotex grids, keeping the weeps themselves soft, pliable and, most important, compressible. Without absolute attentive placement in the masonry joint, their compressibility often can lead to disproportionate weeps across the face of the wall. It is because of this that the rigid cellular-type vents are an ideal choice to maintain air circulation and moisture expulsion at the wall face.
Honeycomb in design and also available in many colors, their placement across the mortar joints in the wall remains uniform in both aesthetics and performance. Of course, none of this makes any difference if the weeps are doomed to fail from the beginning. Mortar coming off the back side of the constricting brick joints will fall to the bottom of the cavity wall, risking the integrity of the open weep passage. There was a time when a mason would run a piece of lumber up the back side of the wall as he lay the brick, collecting the mortar droppings and keeping the wall cavity clear. While extremely effective, it does add a
Mortar coming off the back side of the constricting brick joints will fall to the bottom of the cavity wall.
secondary process, lowering efficiency in laying bricks. Today, we are fortunate to have simpler methods. Mortar collection devices are an imperative component of the wall drainage system, effectively keeping air and moisture moving through the wall cavity.
Failure to understand the importance of quality products can lead to failure. The library at the University of Connecticut is a prime example of the damage water infiltration can cause when an inappropriate flashing is used. Originally constructed for about $24 million, it was a beautiful structure featuring large granite panels. The problems in the wall began almost immediately. Water often would find its way past the barrier of the interior walls, damaging furniture and flooring. Later, the stone veneer began to come apart, some of it crashing to the sidewalk as a result of the anchoring systems succumbing to moisture. It was later determined, among other defects, that the use of an inferior flashing material was a major contributor to the failure of the wall. Today, the beautiful structure remains shrouded in scaffolding, as it's determined who will pay for the nearly $20 million in necessary repair.
The most important part of the veneer wall system is the knowledge of the materials going into it, both in design and construction. Without the understanding of how materials work, how they are to be installed or stored, or how they are affected by the elements, the structure's wellbeing is simply left to chance and assumption. When well constructed, masonry structures are beautiful and strong, yet remain susceptible to extensive damage through moisture penetration. It is never a question of if, but when, moisture will be allowed into a masonry wall, which is why it is so crucial we understand the very components developed to protect it. IMAS Jeremy Douglas is VP of sales and marketing for Sandell Construction Solutions. This article represents one perspective on materials selection for flashing and drainage.