During a recent training class, I was asked an interesting question that I wanted to share with you: How do you firestop a cleanout valve when it lands in a fire-rated wall?
If you encounter this scenario, it is important to consider these three things, in no particular order:
- You need to understand why it is important.
- You need to include a solution in your firestop submittal.
- You need to understand how to maintain the fire rating.
Let’s take these one at a time.
First, Let’s Talk About Why This Is Important
The building code basically tells us that when a fire-resistance rated wall is not symmetrical, we need to conduct a fire test from both sides of the wall. You can read the specifics in the 2021 International Building Code (IBC), Section 703.2.1.1. This is not a new requirement in the code; if you look at previous versions, you will see the same.
Next, you need to look at exception #4 in Section 714.4.2, which tells you that an application similar to the cleanout valve we’re discussing, as well as many other applications, is required to prevent fires from coming through. To this you will probably say, “It’s a fire-rated wall; of course it should stop fire.” However, the building code refers to the ability to stop fire as an F rating, and that section of the code says, “…shall have an F & T rating not less than the fire-resistance rating of the wall penetrated” (emphasis added).
Everyone understands that a fire-rated wall has to have a fire rating, but not so many people understand that in this application, a fire-rated wall must have a thermal resistance as well as a fire resistance. When a fire-rated wall is tested, it must prevent thermal transfer sufficient to ignite combustibles on the opposite side.
To explain why this is important, allow me a moment to explain the fire triangle.
The Fire Triangle
This is a basic image that helps you understand that a fire requires three elements to burn. If you’ve ever sat around a campfire and watched it burn out, you understand how lack of fuel can kill a fire. If you’ve ever used a candle snuffer, you have witnessed what happens when a flame runs out of oxygen. These are the first two legs of the triangle.
To explain the third leg, I’d like to take a different approach. I want you to understand that every room you enter will have oxygen and a fuel load. The third leg of the triangle is the reason we have a T rating. You see, when you have oxygen and fuel, all you need is sufficient thermal temperature rise, and you will have fire as well.
Take a moment to look around the room you are in now. What combustible items are against the wall? Probably artwork, bookcases, calendars, and any other array of combustible items. If those walls are rated, you don’t have to worry because they are fire-resistance rated walls capable of preventing thermal transfer sufficient to ignite normal combustibles on the opposite side—that is, as long as the walls were built the way they were tested.
However, when you have a membrane penetration—a penetration into a wall that does not go all the way through—you don’t know what could be on the other side. The room you’re in is an excellent example. Because of this risk, the building code has the requirements I just shared with you. Now you understand why it is important to ensure that cleanout valves located in a fire-resistance rated wall are properly firestopped, but do you know HOW to do that?
Possible Solutions
Of course, locating your cleanout valves in a non-rated wall is the easiest way to eliminate a fire risk. However, that may not work for your project design, so let’s talk about your options for systems you can include in your firestop submittal.
Following are links to the UL Prospector. You will need to login to access the information; however, access is free, and this is a fabulous resource so you may want to bookmark the link. The five firestop systems currently listed with UL are:
Choosing the Best Option to Maintain the Fire Rating
Let’s walk through a few important things to consider as you select your system because they are NOT all the same.
- Is your wall a smoke barrier? If so, the Hilti detail is the only one that has been tested to provide an L rating that is required on smoke barriers.
- If you have metal studs, you can use the Hilti detail or the STI detail as long as you meet the other parameters.
- If you have wood studs, you cannot use Hilti, but you can use STI, Rectorseal, Holdrite, or 3M.
- If you are working with an uninsulated wall, Hilti is the only system you can use. However, since it doesn’t say insulation optional, it should be used only on non-insulated walls.
- If your pipe is PVC, then any of these systems will work, but if you are working with ABS, then the only detail that will work is STI.
- They all work with a 3-inch drain with a 6½-inch stainless steel cover plate, and they all require the cover plate to be tightly fitted and to have ¾ inch of overlap onto the wall. That means the hole size needs to be discussed with the drywall contractor, assuming they are putting drywall up around the existing pipe.
- They all work with the companies’ respective putty, but some of them have other options as well.
If that seems like a lot of stuff to compare, welcome to the world of firestop done right. Each of these things can impact fire performance in ways you may not be aware of, but that doesn’t mean they are unimportant.
The goal of our Lessons in Firestop is to help you build better. If there is anything else you would like us to discuss, please don’t hesitate to reach out to me directly and let me know what you want to hear about.
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.
