Hose Stream part 3 annular space and sealant depth
Now that you understand the hose stream test a bit more, let’s look at why this information might change the way you inspect firestop. In this segment we will examine two very common errors we find on construction projects. The first is a problem with sealant depth. The second is a problem with annular space, which may actually impact the sealant depth.
As Chad pointed out in his article we shared previously, a thin layer of sealant will not survive the hose stream test. This is why it is important to conduct destructive testing when evaluating firestop installations (both penetrations and rated joints). If the penetration firestop assembly is installed in concrete, there is a good chance that mineral wool is a required backing material. Often, if the installer is not careful how they pack the mineral wool, it will be lumpy. When the firestop is installed over the lumpy backing material the sealant depth will be irregular. It may be thicker than required in one area and to thin in another area. The area where it is too thin can easily be the very spot the hose stream test would fail, if your field assembly were subjected to the laboratory test. This happens both in penetrations and in joint applications where any form of backing material may be used. This is why destructive testing is so critical to ensuring installation conforms to the tested and listed systems. If you are in a jurisdiction where destructive testing is not allowed, I would challenge you to walk the site when the installer is working and check the way they pack the mineral wool before they install the sealant. If it is not compacted uniformly, then the sealant won’t be installed uniformly. If you are going to conduct destructive testing, this quick preliminary walk will give you some insight to what you can expect when you start your inspection. If you are in a jurisdiction that prohibits destructive testing, this can be invaluable to identifying whether or not the installations might conform to the standards.
The next problem we often find is related to the annular space. Let’s revisit the scenario presented when we talked about annular space and continual point contact. We have a contractor who uses a 1” hole saw to make a hole for a 1” pipe. It may sound good, but it’s going to create a problem for a good firestop contractor. The firestop tested and listed assembly will call for a required sealant depth. The sealant needs to be installed in the annular space, which means the assembly into which the firestop is to be installed needs to actually HAVE annular space. Let’s paint a picture in your head of what would happen when a firestop contractor smears sealant around the edge of the pipe to make it look like there is sealant in the right place. Through the life of the building any movement of the penetration cause by pipe hammer, thermal expansion, pipe vibration or anything else would cause this thin layer of sealant to crack or pull away from the wall. Some firestop materials set up rather hard and would crack sooner than other more pliable materials but some form of failure would eventually happen to any material even before subjected to a fire scenario. Now if we take same installation that we have in your head and subject it to the test requirements even before the issues we previously noted have had a chance to occur, the picture you have in your mind should include water coming through the test assembly when it fails the hose stream test. But wait you say, the drywall would stop the water from going through, wouldn’t it? Sorry to say, its not likely. Let’s look at why!
The drywall on the fire side of the assembly is sacrificial and the only thing really stopping the fire is the drywall and the firestop on the non-fire side. Now let’s assume you have a metal pipe, it is going to draw heat through the wall. This will likely char the non-fire side drywall weakening it and creating a scenario where the assembly will fail the hose stream test, so sorry. If you think the drywall will stop the fire in this scenario you are mistaken. It will be brittle and will fail once exposed to the hose stream test.
Next post we will paint a picture that is even more bleak and we will look at how this simple error can create an even bigger problem. If you want to be sure this is not happening on your project, check back and see where we go with this. Until then, keep learning and keep making buildings safer.