Understanding the Risks of Unsecured TPO Terminations in Roofing Projects
In the past few blogs, we’ve taken a look at some examples of extremely incorrect TPO roof installation methodologies. These examples are pretty extreme and what we’re going to show you next is just as bad, if not even worse. We think it’s worth looking closely at examples of improper or bad installation methodologies because it can be a good learning tool. Almost anyone can learn from seeing visual examples, especially if those examples are provided with a narrative to explain the details of the issues.
This past week, we showed the edges of the laps in the seams in this roof, we showed that there was separation and the end of the course of membrane above the lower course was detached and separated. That’s completely incorrect. This is a low slope TPO roof membrane. In TPO membranes, the membrane must be sealed at the edges. Shingles, by comparison, are completely different, they don’t need to be sealed, because they’re installed at a higher slope that keeps them in place and they’re fast and within short intervals. Just for clarity though, we should probably explain that shingles often come with a tacky sealer strip at the nailing area, this strip does allow for some tackiness but it doesn’t actually seal.
You can see a close view of the unsecured TPO field membrane edge in the picture below. My finger is pointing to the bottom of the dunnage under the HVAC unit because there’s another mistake at that location. (Whenever dunnage is set on top of a TPO membrane or whenever a HVAC unit is placed in the field on top of the membrane, it should always be separated with a sacrificial slip sheet. The slip sheet can be literally made from the same material as the TPO, in some cases for low slope roofing, the sacrificial portion of membrane will be turned upside down. In this case though, they’ve used nothing to separate the wood dunnage from the TPO membrane.)
Even though setting the dunnage direct on the membrane isn’t allowed, TPO is one of the toughest membranes to handle wood dunnage placed directly on top of the field of the membrane. The point though is that it’s not allowed by the building code and it shouldn’t have been built like this, they should have simply done what they were supposed to do and installed a slip sheet under the dunnage.
Although this is another small but nonetheless obvious sign that the installers did not build the roof properly, the other issue of the open seams in the field of the membrane, is a much bigger issue. It’s actually a much bigger problem and that issue and will likely lead to leakage into the inside of the building at the first extreme rainfall and or the first time we have conditions of ice damming.
We showed several big problems with the installation of this portion of the roof, but there’s still more. Today, we’re going to look at the terminations of this roof membrane. So far, we’ve essentially been look at the upper portion of this small rear roof area. As we work towards the lower edges, we see other problems with the connection of the membrane to those terminations.
Two weeks ago, when we started this series, we titled the first blog to indicate that using a really cheap contractor doesn’t often save money. This is another perfect example of that same concept because here where they probably used a very inexpensive contractor, this contractor did just about every single detail incorrectly. Not only did they leave issues opened and unaddressed that will lead to big problems, they essentially wasted the TPO membrane because now that it’s been installed incorrectly,in every which way, it can’t really effectively be reused. TPO membrane is expensive, so they basically took that material and effectively rendered it useless. It would have been better for them just to throw it in the trash which is also very wasteful of course.
At the outer edges and lower edges of the roof membrane, you can see, as shown in the picture below, they did not attach the membrane to the gravel stop properly. TPO coated gravel stops can have the field membrane welded directly to the metal termination, but in this case it’s a painted metal termination so it has to be set with a strip-in flashing, instead. Here though, they skipped those parts completely and just adhered the edge of the TPO membrane to the gravel stop with nothing more than siliconized caulking. Siliconized caulkings can work okay for bathrooms, but silicone is a touchy and funny material because it doesn’t work well in all types of applications and in fact silicone can have adhesion problems where it won’t adhere well to certain types of substrates. It’s also almost impossible to effectively apply successive layers of materials directly on top of silicone because silicone, while being a sealant for some applications, is a decoupler for other materials. It can actually prevent successive bonding and adhesion.
Also, if you look at the next picture below you can see that the way they applied this sealant was just by squirting it out of the gun, rough and ugly, without striking it or smoothing it at all and without smoothing the application of sealant. They’ve left areas of voids and omissions. These are places where water can work its way through into the parts below which happen to be coincident with the joint between the edge of the roof membrane and the metal termination.
It simply looks very rough and very bad. But even beyond the application of sealant, there’s a bigger issue which is that the membrane is not properly laid in an overlapped manner and it’s not properly set or welded to the termination.
Here, you can see the exact same issue from a different angle at a different part of the membrane termination. Unfortunately, this issue is consistent throughout the installation.
And of course, the problems don’t end there, everywhere you look there’s another problem, here they installed the gravel stop flashing over the edge of the wall top, but just nailed it in with a ferrous metal fastener. The rusty nailhead sticks out in the photo below. All of the location of fastener head should have been covered with a liberal application of elastomeric sealant, after having the substrate cleaned with a denatured alcohol or similar type of solvent-like cleaning chemical.
This issue of uncovered exposed fastener heads continues throughout the installation. As mentioned, they shouldn’t have used a ferrous metal fastener without it being properly coated with zinc galvanization or another type of treatment to prevent it from accelerated oxidation. The International Building Code and the building code here in Washington DC, as adopted by the municipality, requires that fasteners have to be approved for their particular use: in this case, an exterior installation.
The next picture below shows another example of the gravel stop without a properly terminated membrane connection point.
And lastly, but possibly just as bad as everything else we’ve shown, the next picture below shows the rear termination of the membrane without a drip edge, in this case they just passed the membrane over and folded it down on top of the edge of the gutter and nailed it to the fascia or sub fascia with ferrous metal fasteners which are now rusted.
Problems like this could be easily avoided by using a better contractor. We recommend every building owner in DC who values the longevity of their roof (and their investments) and building use a contractor who values the simple and important principles of proper roof construction like Dupont Roofing DC. Learn more about our company and the proper techniques of working with roofing on historic buildings in Washington DC here on our blog at DupontRoofingDC.com, and you can call us at (202) 840-8698 and email us at dupontroofingdc@gmail.com.
