Fechino Files: Weeps and Term Bar

Words: Steven Fechino

I hope you are getting through the cold of the winter without issue, maybe even enjoy throwing a snowball (not an ice ball) at a coworker that deserves it. This month I thought I would do a quick primer on basic flashing installation. As many will have new hires, this may be used at a foreman meeting or just for new hire training.

How to Install WeepVents and CellVents

Weeps found in the base of masonry walls have been part of masonry construction for over 50 years. The purpose of a weep is to allow moisture that finds its way between the veneer and the structural substrate a clear path out and away from the structure. Typically, early weeps were just open head joints at the base of the wall placed approximately every 24 inches, but quickly many versions from metal louvers, Plexiglass tubes, to cotton rope began to fill the market with alternatives that would prevent insects from entering the open joints. Over the past 50 years, weeps, like everything else, have undergone several different design versions, many of which worked very well, to a few that did not function well in humid parts of the country. Today, there are two common weeps that are typically placed in the head joint directly on the base flashing, allowing any moisture that finds its way to the base of the wall an easy path to the exterior of the veneer. The more common CellVent, a polymer-based set of multiple channels for water to pass from the cavity to the exterior, and the WeepVent, a high-loft, non-woven, non-directional polymer mesh, which accomplishes the same task.

WeepVents and CellVents serve two basic functions for a veneer wall. They provide a clear path for drainage and also allow a clear path for ventilation of the cavity when placed at the bottom as well as the top of a cavity wall. A properly placed weep needs to be directly placed on the through-wall flashing (not on the bed joint) for proper function. When used additionally to increase airflow, the weep should be placed in the last fully exposed course at the soffit or the shelf angle to allow for a chimney effect for air to draft out of the cavity and increase drying of the full system.

Weeps can also be placed horizontally directly on the flashing in the bed joint. Simply place a shim pack on the left and the right of the weep (one that fits the bed height) and place the weep between the shims. The reason for this application is that it can prevent head joint cracks in taller base stone where the weep is only a fraction of the height of the head joint of the material. It is quicker to install, can be neater in most cases, saving labor and giving a better-looking final product in the end.

The durability of polymer-based weeps is a topic that has been discussed by many, but here is the long and short of it. Many through-wall flashings are placed within eight inches from grade. Many weeps are placed behind landscaping or under a soffit that can block direct sunlight. In addition, the sun typically only has direct exposure to two elevations at any one time, but not fully continuous through the year. Exposure to a weep is minimal at best. The bigger action that attacks a weep is the person behind the pressure washer during initial masonry cleaning or servicing of pressure washing to enhance the veneer during the life of the structure.
Single wythe walls should not have a head or bed joint weep placed in the wall. Mortar Net Solutions can offer alternatives if your designer requests weeps for a single wythe wall.

Term Bars

Termination Bars, Term Bars or T Bars—whatever you choose to call them—should be on every piece of flashing you install, no buts! They are not fun to install, but they are not hard to install, cost relatively little compared to repairing a sagging flashing that has been covered up, and they really give you peace of mind when laying the brick because you know you have the confidence of a properly secured flashing.

There are different types of term bar available. T1, which is a flat stock with pre-drilled holes typically on 8-inch centers, and T2 bars, also pre-drilled on 8-inch centers. The difference between T1 and T2 is that T2 has a bend on the long side to allow for additional sealant to accumulate in the gap and provide a better seal and a better bridge for moisture that finds its way over to the flashing to the bottom of the flashing. Mortar Net Solutions also stocks a PVC high-density term bar that does not corrode, can be cut with tin snips, and has both flashing and waterproofing uses.

Installation

When installing a term bar, it is important to have all of the tools and materials you will be using readily available and mobile. I use a carpenter’s pouch; it holds my drill, my impact, and my anchors. The only thing I need to carry is the term bar and the messy sealant gun. Unlike when I began in this industry, flashing was once commonly tucked in the bed joint of the substrate. Today, we install the flashing as a separate task due to changes in substrate makeup, scheduling, and trade assignments. As the flashing is pushed up the wall, beginning at the face of the bed joint, you can locate the term bar once it is fully extended up the wall, usually only about 12 inches. I place the term bar in the proper location and set the first anchor, starting in the middle of the term bar, and work my way out left and right. If I am by myself, I will loosely install the term bar without sealant, get everything aligned, loosen the anchor screws, install the sealant behind the term bar at the top of the flashing, and snug my screws causing the sealant to ooze up above the in-place term bar. Simply then, slick the ooze parallel with the top of the term bar, and you have successfully created a bridge for any moisture that appears on the substrate, providing a clear path for it to get to the weeps.

Personally, since I have been at this for over 40 years, I decided a long time ago that I will anchor term bars with screws, not compression anchors, because if I over-compress a term bar’s anchor, the flashing can bulge (fish mouth) and create an opportunity for water to go behind the flashing—not today, but over time—as sealants cure, dimensional changes occur, and hairline gaps can become present. I can always loosen a screw and correct the original installation. The worst thing I could do is tighten the screw too much. In addition, screws do not need to be driven home. Snug screws, proper placement of sealant between the substrate and the back of the flashing (creating a gasket), will offer lifelong performance able to handle all thermal, compressive, and lateral loads a building exterior has during the life cycle of the structure.

Enjoy the rest of the winter. We will be cutting grass each week before we know it!

Fechino Files: Weeps and Term Bar

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