This is a 1-hour wall that separates an exit corridor from a condo unit. We are looking at it from the unfinished condo side and the firestop has been installed from the corridor side. From the corridor side of the wall, the installation looks good at a glance. The firestop is installed the full circumference around the cables. The cables are rigidly supported as required by the UL listing. The installer used an intumescent material that matches the submitted UL listed detail. When the wall is complete these MC cables will not penetrate the room side of the wall so technically this is a membrane penetration rather than a through penetration, but UL requires the same installation regardless of this fact. Bare in mind, this is changing and UL is requiring that membrane penetrations be tested separately, because they may perform differently than a through penetration. Stay tuned for more on these changes in the coming posts. Can you tell what is wrong with this installation? Better yet, can you explain why it is wrong and more importantly, two other issues. 1) What might the impact be in a fire scenario? 2) How might this improper installation impact the project over time?
Most UL listed firestop details will require 5/8” depth of sealant. I can tell you that the installer did not achieve even half of that. If you look closely, you too can see this just from looking at the picture. You can see that there are 2 layers of drywall. You can see an ever so faint line at the top of the opening where the papers from both layers of drywall are in contact. That means that the line between the two layers of drywall would mark 5/8” depth of sealant. As you can see, the installer did not even come close to achieving the required depth on this installation. Then, if you want to go on further to critique this installation, there is very little drywall between the hole on the left and the center hole. Furthermore, there is NO drywall between the center hole and the one on the right, so technically this is one opening. As such, most UL listed details will require that the cables be tightly bundled, which they are not. When cables are loosely laid together, there are a few problems. First, the installer can’t easily get sealant between the gaps around the cables; so this means the sealant depth is not achieved. Further, the gaps increase the risk of cables moving and the chance of the sealant pulling away from the opening or adjacent cables is increased which can lead to a failure of this installation in a fire scenario. These gaps are a weak point for both reasons.
Impact in a fire scenario: One of the steps in testing a firestop system is a hose stream test. This portion of the test is designed to judge the integrity or durability of the installation because during a fire there is a lot of pressure in the room of origin and a lot of movement of the various elements in the building. We want to know that the firestop system will have the integrity to withstand the impact of these things. Every fire will be different, so no one can say for certain what dynamics any firestop application must endure, but if a PROPERLY installed firestop system is subject to a real world fire scenario we have a good idea of how it will perform. This installation is not a properly installed firestop system and while I can say it will definitely fail, I can say that this installation presents a liability for the firestop installer, the electrical contractor, the GC or CM, the owner, the buildings insurance company and the occupants of the building. Don’t worry, the firestop contractor was required to remediate this particular problem on this project. Please make sure they do the same on your project. For more information about the hose stream test check out these other blog posts as well. Here is one example.
Impact over life cycle of the building: There are a myriad reasons why the cables in this picture might be bumped, jostled or otherwise moved in a way that could dislodge the thin layer of firestop. However if the sealant is installed at the required depth of 5/8” and there is movement, the firestop material will likely still remain in the annular space of the opening. This means, it will be in the proper location so it can perform as expected, even if it pulls out of the wall slightly over time.