April 2023 Lessons in Firestop: How to Firestop Metal Pipes at an Angle

Lessons in Firestop by Sharron HalpertHow often do things work exactly like you plan them? I don’t know about you, but I think the larger part of my life has gone contrary to my plan—but that’s not necessarily a bad thing. It doesn’t mean that I made bad plans. It’s just that in life, we often have to do things a bit differently than we may have thought.

Construction is not much different. If you think about the last few projects you’ve worked on, did you have any pipes running at an angle? If you did, did you properly firestop them? If you have the right conditions, this may not be an issue at all. However, if you have the wrong conditions, you could be facing a really expensive solution…or a liability because you didn’t do things right. This article will help.

What’s the Problem?

Let start with this: When firestop is tested, the pipes will run at a 90-degree angle to the rated floor or wall—unless the detail specifically says something different. We aren’t really worried about a pipe at an angle through the floor, at least not with anything I have ever seen. The walls are a different story though. When you have a pipe at an angle other than 90 degrees, you should ask yourself one question: Is there anything combustible? If it is a combustible pipe, things just got complicated. If there is combustible insulation on a plastic pipe or even on a metal pipe, you could have issues as well.

Rules to Follow

Today we are going to talk about how to ensure metal pipes at an angle are firestopped properly. You need to check for a few key things. First, we are addressing only bare metal pipes at an angle because you are not allowed to run insulated pipes or plastic pipes at an angle without some really unique firestop solutions. Those discussions will come later, but for now we are focusing on bare metal pipes and will go over the rules you need to follow to avoid liability.

#1: Size and Type

When you have a bare metal pipe running through a rated wall at an angle, take a look at the firestop detail. It doesn’t matter if you are dealing with a concrete or block wall or a gypsum wall—this first part will be the same.

Be sure you have a firestop detail that matches the fire-rated wall. That detail needs to allow for that size and type of pipe. Most metal pipes are going to be steel, cast iron, or copper. However, if you are working with aluminum, brass, or bronze, the fire dynamics are different. You see, aluminum melts at a much lower temperature than other metals, so you have to be sure you have a firestop detail that will work for that. If you have brass or bronze, this is basically copper with either tin or zinc, which makes the copper perform more like a plastic when it’s subjected to fire. Again, you need to have a firestop detail that will allow for that particular size and type of pipe.

#2: Annular Space

Look at the firestop detail. What annular space is allowed? If the detail says an annular space of 0–1 inch, that means (obviously) that the pipe can touch on one side, in one location, and that you can have up to 1 inch in any location. I want to point out two things here.

First, if a detail allows for 0-inch annular space, that does not mean the pipe can touch the edge of the opening all the way around. It means that if you have a pipe pushed off to one side, then it can touch there, but you have to have annular space in the other locations—and it has to be enough annular space to install the required sealant depth. This is important to get right if you want the firestop system to perform properly.

Here is the problem: When a pipe goes straight through a wall, it goes through a circular hole, but when the pipe is at an angle, the hole has to be oblong. This often means your annular space on one side of the wall will be different from the other side, and you still have to conform to the requirements of the submitted and approved firestop detail.

If you ever need something more than this article to explain this, please visit the UL website. You will have to register, but it is available for free. If you go to the XHEZ document, you will see this as of April 2023:

“Where the uninsulated penetrating item in the individual design is indicated as a metallic pipe, conduit, tube, duct, or cable, and the firestop system consists at minimum of a fill material (such as sealants, putty, or mortar), the penetrant may pass through the opening in the wall or floor assembly at any angle, provided the annular space is maintained on both sides of the wall or floor assembly and all other specifications in the design are satisfied. In all other cases, except where otherwise indicated in the system, the penetrating item should penetrate the wall or floor assembly at a 90-degree angle.”

Please note that this XHEZ document is subject to change, so check the UL site regularly so you have up-to-date information.

In Summary

To wrap this up, if you have a pipe that is at an angle, you should follow these rules:

  • The annular space matches your firestop detail
  • Only bare metal pipes
  • No insulation
  • No plastics

So now you know how to address a metal pipe that is running through a rated wall at an angle (other than 90 degrees). Our next discussion will explain why you cannot expect a combustible penetration to perform adequately when it is at any angle other than 90 degrees. If you work with plastic pipes, please join us for that discussion. See you there!

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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