Installing Flashing in Various Conditions

Words: Dan Kamys

Flashing and Drainage

By Steven Fechino

Flashing and Drainage Many technical questions regarding flashing are based on conditions that didn’t exist a short time ago. Grade differentials, bed depths or brick shelf dimensions, arches and piers are just a few details that can add significant time to your project if they are not properly evaluated and considered during the estimating or buyout phase. Most contractors realize that flashing installations are not always routine; in some cases, they can be downright tough. Many different conditions can affect the installation of the components. As we estimate our work, we should be on the lookout for a few details that can add material and labor costs. Cavity walls today are constructed over various grade differentials, with step-downs and all different bed depths or brick shelf dimensions. Arches can pose challenges, brick returns at door jambs are always frustrating, and piers and pier corners can add time to a project that in some cases was not considered at earlier stages. Piers or column wraps have become very common on larger commercial buildings over the past few years. The piers can be hollow, where a larger cavity creates an architectural feature, or they can surround a structural element, such as a column of steel or concrete. In both conditions, the flashings must be constructed for effective and economical functionality. On columns where the cavity is filled with a structural element, the challenge is greater for economical flashing installation, as components can become expensive when multiple corners are involved.

Elevation of the Flashing

[caption id="attachment_13572" align="alignright" width="300"]Brick Shelf 1:  Install the prefabricated stainless steel drip edge corner in a bead of sealant. Brick Shelf 1: Install the prefabricated stainless steel drip edge corner in a bead of sealant.[/caption] The first item to address is the elevation of the flashing. Many manufacturers’ recommendations are the same: flashings should be placed above grade and below the finished floor — which is common sense. However, this is becoming difficult to achieve for many projects because the flashing level is shown on the finished floor with the exterior grade at nearly the same elevation. As a contractor, you find yourself caught between what is best practice and the limited options you have for this condition. Even if you write a letter or a request for information (RFI), you may end up no better for trying. So what can you do? [caption id="attachment_13573" align="alignleft" width="300"]Brick Shelf 2: Install two boot extensions with a perimeter bead of sealant that oozes at the joint on each side of the corner, extending approximately 1/2 inch from the drip edge bend. Brick Shelf 2: Install two boot extensions with a perimeter bead of sealant that oozes at the joint on each side of the corner, extending approximately 1/2 inch from the drip edge bend.[/caption] The installer’s best option is to use butyl sealant. Developed in 1937, butyl has been around a long time and has a proven track record. It’s ideal when flashings need to be installed in a location where water is assumed to travel under the membrane either by capillary action or by an excessive water event. Place several beads of butyl parallel with the face of the veneer, approximately 1 inch from the face of the veneer and several inches deep within the wall. Here is where common sense is needed. Consider the site conditions to make sure you do not have excess material that might be exposed after your work is completed. Butyl is a non-curing product that will remain sticky forever. It is forgiving and can be pulled apart many days after installation without destroying the flashing or sealant in case a repair is needed. Butyl will bond directly to itself even many months later, regaining full integrity as a sealed lap.

Cavity Depth

[caption id="attachment_13574" align="alignright" width="300"]Brick Shelf 3: Install a membrane patch with a perimeter bead of sealant that oozes at the joint with a small, 2-inch cut placed directly at the corner and extending within 1/2 inch of the drip edge bend. Brick Shelf 3: Install a membrane patch with a perimeter bead of sealant that oozes at the joint with a small, 2-inch cut placed directly at the corner and extending within 1/2 inch of the drip edge bend.[/caption] Once the placement of the flashing elevation has been established, the depth of the cavity needs to be addressed. Until recently, we did not see bed depths greater than about 7 or 8 inches. Though these larger bed depths are greater than a few years ago, we could easily manage the additional dimensions. Now we are seeing depths of 10 and 11 inches at many building bases where stone is featured. This is a bit of a game changer because the added bed depths create larger corner gaps, and standard components will need adjustments no matter who manufactures them. The process I will discuss encompasses standard flashing components used in the industry. This is another area where common sense kicks in. When dry fitting the column where a bed depth is very large, say 11 inches, the first step is to install the stainless steel prefabricated corner. In this situation, the corner components commonly stocked by most distributors will not allow you to install flashing without cutting it. The easiest alternative is to extend the prefabricated stainless steel corner from 7.5 to 12 inches in both directions. [caption id="attachment_13575" align="alignleft" width="300"]Brick Shelf 4: Install the preformed corner boot with a perimeter bead of sealant that oozes at the joint, as shown. Brick Shelf 4: Install the preformed corner boot with a perimeter bead of sealant that oozes at the joint, as shown.[/caption] With the drip edge in place, the next steps can begin. Before installing the corner boot, cut two pieces of membrane and install them so they are above the corner boot in height on the substrate, so that a small term bar can be installed on each side without interfering with the term bar on the base flashing panels. Extend the membrane sections approximately 9 inches in each direction from the corner and all the way to the front edge of the stainless steel drip edge where it bends down. This additional membrane will be under the corner boot and placed on top of the drip edge. Keep in mind that, in this case, the corner boot will be short of meeting the drip edge by about 4 inches if you include the proper lap. Here is what we have found to work well. Simply cut a piece of patch membrane that is approximately 3 inches larger than the void on both sides. Place about a 2-inch cut in the corner of the patch that will rest in the seam of the corner. [caption id="attachment_13576" align="alignright" width="300"]Brick Shelf 5: Begin installing your base flashing, aligning the drip edge with the prefabricated corner piece.  Follow all standard base flashing installation procedures. Brick Shelf 5: Begin installing your base flashing, aligning the drip edge with the prefabricated corner piece. Follow all standard base flashing installation procedures.[/caption] This patch is placed with a full bead of sealant around the perimeter and, when placed, will create an ooze around the perimeter that assures you that water will not find its way underneath the patch. Once the corner flashing patch has been installed, there is no cutting or folding of flashings around the corner, thereby preventing any possible leaks that can occur with voids in flashing sealants or cutting of membranes. Another advantage of doing it this way is that the installer can pre-cut what he needs and stock it in front of the bricklayers. A specialty crew is not needed to install the flashings. With the patch in place, simply install the prefabricated corner boot with a bead of sealant around the perimeter of the setting area and allow it to create another ooze joint around the boot. Then place the flashing down the wall. This technique will work for both inside and outside corners with large brick shelf dimensions. The entire corner should only take a few minutes, reducing the opportunity of flashing errors or leaks and keeping your bricklayers productive.
Steven Fechino is engineering and construction manager with Mortar Net Solutions, makers of TotalFlash and BlockFlash. For more information, call (800) 664-6638, or visit www.mortarnet.com.
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