Improper Termination Bar Installation
Termination bar is used to secure and seal single-ply membranes at parapet walls and other penetrations. Usually made of extruded aluminum – 1/8 inch thick and 1 inch tall with pre-punched holes for fastening – term bar is sold in 10-foot-long sticks.
The term bar detail is simple. The bar is placed at the top of the flashing and fastened in place. The standard detail requires that a bead of water block be laid behind the membrane and a bead of sealant be applied on top of the bar. (See Figure 1.) Pretty hard to mess up, right? Wrong.
When used in the appropriate applications and installed properly, term bar is a tried-and-true solution for finishing off flashings. As with most things in life, it is designed to be used in a certain way – installed horizontally on a vertical surface. Unfortunately, roofers often use it outside of those conditions, and the results can be the stuff of roofers’ nightmares.
Termination bar should not be installed flat on a horizontal surface as was done on the job shown in Photo 1. Doing so will inevitably result in leaks. The termination bar detail was designed to be hydrokinetic, or water-shedding. Mounting term bar flat on horizontal surfaces instead creates a hydrostatic condition in which water could periodically cover the bar, allowing water in. There are better solutions to address these scanarios, such as coping caps or drip edges or simply moving the termination point to a nearby vertical surface.
Another common error that contractors make when installing term bar is bending it around or into a corner. Photo 2 and Photo 3 show the result -- gaps. Most corners on a roof are a sharp 90 degrees (or nearly so). Termination bar is just too thick to be bent and properly fit into a square corner -- particularly inside corners. It should always be cut and tucked tight into a corner, with a fastener installed within 1 1/2 inch to 2 inches from each end, enabling it to provide constant compression on the flashing membrane all the way to the corner.
While term bar is primarily installed horizontally on vertical surfaces, it can also be installed vertically on vertical surfaces. Contractors often neglect an important step when doing so, however, opening the door to leaks. When installing term bar vertically on vertical surfaces, both sides of the term bar must be sealed (see Photo 4). Think about it. When term bar is installed horizontally on a wall, the top edge is sealed to prevent water from going behind it. What happens when it's turned 90 degrees? There are now two sides where water can enter. Both sides must therfore be sealed.
Finally, a recommendation regarding choosing fasteners to install term bars. The photos accompanying this article show several types of fastener being used – lead hits, threaded fasteners and nylon hits. We recommend using threaded fasteners, and here is why. If, for whatever reason, the termination bar must someday be removed or repositioned, the only way to remove a lead or nylon hit is to grind it off. This can easily damage both the termination bar and the wall to which it is mounted. Threaded fasteners, on the other hand, are easier to remove and their removal is unlikely to cause any damage.