September 2022 Lessons in Firestop: Firestop Is Lazy

Lessons in Firestop by Sharron HalpertCalling firestop lazy might seem like a strange thing to say, but it’s true. If you want to build better, then you need to understand this simple fact. Let me explain.

You probably know some lazy people. They do as little as possible until something happens to make them do a bit more or sometimes a lot more. They are not often self-motivated, and they need direction to do almost any task. Well, if firestop were a person, it would be a lazy person because it needs something to push it into action, and it also needs direction and guidance.

Have you seen projects where the plumber needs to go through a gypsum wall and they bash a hole in the drywall? Well, what they have just done is take away the guidance and direction that our lazy firestop needs. You see, firestop sealant expands in the area of least resistance, so when you have a clean-cut hole and a pipe through the hole, the firestop will expand directly against two parallel surfaces: the cut edge of the drywall and the pipe. When the plumber bashes a hole in the drywall, the pipe and the opening are not parallel, so when the firestop expands, it is more likely to slide out of the annular space and mushroom away from the space it is supposed to close up. This is obviously going to be more critical with a plastic pipe or an insulated pipe than with a bare metal pipe, but good habits are good habits regardless. If your field crews are bashing holes in gypsum walls, please ask them to start with some good habits—at least if they are working on a fire resistance rated wall.

So now let’s pull things together:

  1. You have to have the right-sized hole (you know that from the Goldilocks story).
  2. The hole has to be the right shape.

You want to know something about firestop that your middle school geometry teacher would NOT want to hear? There is no difference between a square and a circle. You see, when it comes to firestop, it doesn’t matter if you have a square opening or a round opening, unless it is specifically called out in the tested and listed detail. This isn’t just your favorite firestop chica telling you this. You can see it in black and white when you go to UL’s website and read about what they call the XHEZ guide. (You may have to log in to the website, but it’s free and a fabulous resource for so many things that we will dig into at some point!)

Here is what it specifically says:

“The annular space of a penetrating item through a rectangular opening is determined by measuring the distance from the closest point of the penetrating item to a point perpendicular to each of the four sides of the opening. The diagonal dimension is not intended to represent the annular space of a rectangular opening.”

So, if you are looking at a firestop detail and it doesn’t specify the shape of the opening, it can be round or square, and you can firestop it the same way with the same firestop detail, using the same materials. What you CANNOT have is a jagged-edge, spalled-out opening. The edges have to be straight with clean cuts—otherwise the lazy firestop will go in the area of least resistance, which is typically not where you want it to go.

When you look at a firestop system, it will typically call out the annular space with a minimum and a maximum space. The old firestop systems, or some of the new systems for mass timber, will call out a nominal annular space. These are not typically practical systems because you are saying the pipe will be centered in the opening. That doesn’t really happen often, so what happens is that most people ignore it and do “whatever.” This is a litigator’s dream. Life safety is a key word that would catch anyone’s ear in court, so let’s make sure your teams are doing the right thing, shall we?

One more thing to keep in mind: if you have a combustible penetrating item such as a plastic pipe or an insulated pipe that will melt or soften in a fire scenario, then all of this becomes just a little more important. Please, if you have not been paying attention to this on your projects, start looking closer. If you have been paying attention to this, congratulations and thank you. Now go make sure the rest of your team is doing the same thing. Share this post and others and help us spread the word to help people build better.

If you have any questions, comments, or even topics you want me to cover, I would love to hear from you.

Connect with Sharron

A former kindergarten teacher turned firestop expert, Sharron is President of Halpert Life Safety Consulting LLC, a leading provider of firestop-related life-safety and passive fire protection solutions.

If you like what you read here and want to know more, email [email protected] or connect with her on LinkedIn or Twitter to tell her what else you want her to cover in this column. You can also follow her on Instagram. If you find this information valuable, please like, share, comment, repost, retweet, and throw it on IG to help people build better.

The opinions expressed in this article are those of the author and not the American Society of Plumbing Engineers.

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