When I sat down to write this article, I began by looking at the designated topic: What we do to manage mortar droppings. As I wrote, the words flowed with ease answering the typical questions: Why are mortar droppings a problem? What have we done to address these issues to date? What are the commercially available mortar collectors, and what makes one better than another?
As I read what I had written, I practically dozed off. This information has been studied, written and read many times by countless others. I confirmed my belief by searching for the phrase "mortar droppings" on Google. The search returned 17,100 results. With the echo of endless repeated political ads still ringing in my head, I decided now is not the time to reiterate that which you already know: we need to manage mortar droppings.
But then what do I discuss? How do I bring a new approach or point of view to a consensus we collectively reached long ago? A need to rehash the issues comes yet again.
There are two major issues when it comes to managing mortar within the cavity: the need to ensure weep function and the need to address mortar bridges throughout the entire height of the airspace.
Mortar droppings are excess mortar that fall to the flashings. Mortar droppings obstruct a properly detailed and constructed flashing system, blocking weeps and preventing the drainage wall from functioning. An initial means of protecting weeps from mortar droppings was to place pea gravel in the cavity. We quickly learned that this did not resolve our issues we merely raised the location of the solid ledge of mortar to the top of the pea gravel.
A huge improvement over pea gravel came when commercially available drainage materials were introduced to the marketplace. These products come in various configurations, all of which break up mortar droppings in one manner or another to reduce the opportunity of creating a solid obstruction above the weeps.
The second issue is mortar bridging. Mortar bridges occur when mortar makes contact with the backup. When mortar makes contact with the backup, a mortar bridge between the masonry veneer and the backup is created (see photo). A mortar bridge will impede the flow of moisture to the flashing level, and it will make it harder for air to flow within airspace. Moisture can pond on top of mortar bridges. If moisture is collecting at locations where insulation joints are not properly sealed, moisture will have the opportunity to get behind the insulation. Building owners are extremely sensitive to moisture-related issues, and mold has been surfacing as the number one concern in all building envelopes.
Practices to prevent mortar bridges have included the use of pull-boards and back parging. Pull-boards are a hassle, and this practice can disturb bricks. Back parging can increase the amount of mortar droppings. Recently, we are adding open-head joint type weeps at the bottom and the top of the wall, sometimes with plastic or mesh inserts. This practice greatly improves cavity ventilation, yet cannot compensate for a severely obstructed cavity.
Our practices to prevent mortar droppings from blocking weeps are also not without concern. Most agree that the success of a mortar dropping collection device depends on how well it stages the mortar droppings in such a pattern that will reduce the chances of a solid obstruction. But even the best available mortar dropping collection device is sometimes not enough.
First, it is possible that enough mortar can fall on top of a two-stepped material so that mortar spans the upper tails. Secondly, at an average of 1-2" of mortar droppings per foot of wall height, the lower step can easily become obstructed with mortar as well. Thirdly, no mortar dropping collection device attempts to deal with mortar bridging higher up in the wall.
Refer once again to the photo. The mason who was constructing this wall was asked, "Hey, I thought you weren't supposed to have mortar making contact with the insulation like this." He responded, "It doesn't matter. I have a [mortar dropping collection device] at the bottom." I am sure this mason was not a reader of this magazine, nor a member of a trade organization that ensures its membership is informed and has attention to quality. Yet nonetheless, this belief does exist. And though full education is a continual goal that we are striving toward, I doubt it will ever be completely reached. Levels of experience, knowledge and workmanship definitely affect outcome. But financial and time constraints sometimes force masons to emphasize speed over quality, and even the most skilled mason can be challenged to construct a completely clear cavity wall.
Responding to this challenge, several companies now manufacture products that are installed throughout the full height of the airspace to assure a clean cavity. By installing a full-height drainage material that does not allow mortar to make contact with the backup, a continuous drainage area is the result. Additionally, these products make smaller cavities possible, which allow increased insulation or overall wall thickness reduction. Even though these products have quite different physical properties, the concept is still the same: full-height airspace maintenance that prevents both mortar droppings and mortar bridging. Anything else is only solving part of the problem associated with mortar management.
There are a number of masonry wall designs that are constructed every day, but for the mason there is one wall design that may be the greatest challenge when it comes to managing mortar. The cavity wall is considered by many to be the optimal brick design for successful masonry buildings, but it can have problems due to excess mortar in the airspace and at the flashings. We have read many articles that document the need for a clean airspace and unobstructed weeps. There are several schools of thought to manage mortar in the airspace. Only one is emerging that can handle all of the problems that mortar droppings create: a full-height drainage material that completely prevents mortar droppings in the first place.
Well, sorry, I have done it again. By the time this magazine reaches you, my Google search will produce 17,101 results. But alternative approaches are taking hold, and maybe over time we can move our discussions from the question of how to keep a cavity wall clear to something equally interesting and important.
"Drainage systems" in masonry cavity walls seem to be becoming a catch phrase.
It's true that proper drainage in a masonry wall is essential to ensure the performance of all masonry structures. Masonry buildings have stood the test of time. Known for their strength, beauty and longevity, masonry structures are a statement of our past, present and future.
As one example, the proper use of quality masonry flashing is the one sure way to protect against moisture migration in a masonry structure. Copper flashings have long been the flashing of choice, providing decades of moisture protection. Only copper can boast a success story that dates back over 100 years. Resistant to all harmful effects of the acid and alkali present in fresh mortar, copper will out-perform all other flashing products. And, as mason contractors, you know that it is always important to get the most out of every construction dollar. An investment in copper flashing will bring a worthwhile return on any construction investment. Conversely, PVC and rubberized asphalt membranes presently being marketed as masonry flashings exhibit no characteristics to promote long life. It might be worthwhile to ask the manufacturer of your chosen flashing product to state the performance life of their products.
The Brick Institute of America suggests that a properly constructed brick wall should last at least 100 years. The cost of replacing failed flashing is outrageously expensive, and inferior flashing still remains the predominant cause of moisture migration in a masonry wall. Does it make sense to put retreads on a Rolls Royce?
Another example arises as we continue to learn more about the importance of positive airflow in cavity wall construction. This positive ventilation promotes the drying process of the interior cavity, thus retarding the possibility of mold growth. The Mortar Break® system by Advanced Building Products was the first geosynthetic mortar deflection device, dating back to 1989. Independent testing by Architectural Testing Inc. proves the Mortar Break system provides for proper moisture drainage in a cavity wall while supporting positive airflow.
Recently, the performance of straight cut mortar deflection and airflow-enhancing products have been questioned by a competing company that markets a dove tail-shaped product. The test results are in, and both the straight cut Mortar Break system and the competing dove tail product do a good job in keeping the cavity clean and water draining from the cavity. The independent testing also revealed that, when proper weep vents are installed, the airflow ventilation allowed by the straight cut product exceeded that of the dove tail products.
With this misunderstanding cleared up, the masonry industry is free to use either system. An informed consumer always benefits by honest competition.
Masonry construction dates back to the beginning of the construction industry. A proud past and a promising future lie ahead for the masonry industry when value engineering does not compromise quality products.
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