1 hour wall ~ Submitted Firestop Detail: HW-D-0134 ~ Structural Engineer calls for ½” of movement.  Just looking at this firestop detail and this image, can you find the problem?  You can slide the photo to reveal the issue.

The drywall is tight to the underside of the deck so when there is movement in this finished wall, one of two things will happen. Either the drywall will crack as the deck above deflects towards the wall or the firestop will split as the wall moves away from the deck above. That is just one of the problems though,

If you look at the firestop detail however you will see that even if the gypsum board was installed with the largest joint allowed in this firestop system, which would be ¾” joint, the 17% movement would not be capable of meeting the requirements of the structural engineer.




1-hour fire rated gypsum wall ~ Submitted detail W-L-3350~ Penetrating items: Metal Clad Cables & Flexible Metal Conduit.

This photo shows you my favorite little cheat, when confirming firestop compliance. Most gypsum wall details require 5/8” depth of sealant for one-hour walls, basically because without a sleeve you can’t get any more in place. This field condition had a second layer of drywall for acoustics. If you look closely you can see where the two boards meet and if the installer got 5/8” depth of sealant, you would not be able to see that line of demarcation between boards. So, with that I gave you the EASY, problem. Can you see the other issues?

Problem 1: The firestop system requires the cables to be tightly bundled together, but clearly they are not.

Problem 2: The firestop system allows MC cables, but this is actually three flexible metal conduits (1000 series system) and two MC cables (3000 series system). I’m not saying I would fail it because of this, but I would want to confirm with the firestop manufacturer to be sure this is okay.

Problem 3: W-L-3350 allows for a max opening of 3”. I can’t tell from the photo but if you were in the field you certainly would want to verify this.

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These are the non-dampened ducts in a 1-hour block wall. Let’s assume the duct on the left is 16”x32 and the one on the right is 26×38. The installer used the proper depth of mineral wool and the proper depth of firestop sealant. They claim they are done.

Can you spot what is missing?  You don’t even need a firestop detail because this is a physics problem that will exist for any application that is 1) this size 2) not insulated 3) not dampened.

Any time you have a non-dampened, bare duct over a certain size it will require retaining angle. The reason is one part physics and one-part thermal dynamics and it has to do with the Coefficient of Lineal Thermal Dynamics. This scenario requires a retaining angle be installed on both side of the wall. The angle must be attached to the duct. The angle needs to lap on to the duct 2” and onto the wall 1” (which means 1” plus the annular space. So, if you have 1” annular space your angle should be 2”x2”. If you have 2” annular space around one side of the duct the angle needs to be 2”x3”.  There is a whole lot more to it, so if you deal with this scenario, please check out the blog for more information.

If you would like more information on this, just go to our blog post here!


The building code requires that fire rated walls be labeled and some project specifications require the firestop installations to be labeled. If your team does not know the naming system used by UL; they are going to struggle to find the proper details to put on the label. Keep in mind, they are supposed to be using the firestop submittal to direct their installation. If they can get the label right, do you think they even know the specifics of the firestop system? All it takes is a lawyer who knows this nomenclature and this firestop installed has some serious litigation to deal with. My challenge for you…do you know what is wrong with the UL detail listed on the label?

NOTE: We need to blur out  sections of this photo that identify the company or project

This one might seem like a silly thing to “pick on”, but it speaks volumes to a firestop installer or an inspector. In this case the guy could not have gotten it any more wrong. The naming system has two parts. The ABC’s followed by the 123s. the ABC’s tells you about the rated assembly. The field condition is a gypsum wall. This should be WL. They listed CAJ, which is for concrete floors or walls. The next part they screwed up is the 123 section. 1000 series details are for metal pipes. This is an insulated pipe so that should be the 5000 series details.  If you deal in firestop, you NEED to know this.

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This is a 1-hour G500 floor/ceiling assembly and a 2”PVC pipe through the ceiling assembly. Submitted detail F-E-2013

Have a look at the firestop detail as well as the installation instruction for the firestop sealant. How many issues can you find with this installation?

Firestop detail  : https://multimedia.3m.com/mws/media/197681O/system-no-f-e-2013.pdf

install instructions :https://multimedia.3m.com/mws/media/207329O/3m-fire-barrier-sealant-ic-15wb-technical-data-sheet.pdf

Problem 1: The installation instructions say you have to install the firestop sealant to a cleaned to allow for proper adhesion of the firestop

Problem 2:  The installation instruction call for the firestop sealant to be tooled within 5 min.

Problem 3: Sealant depth is to be 5/8” in the full annular space, but because this drywall section is broken it’s not possible for the installer to get this right.

If you have a project with this sort of floor ceiling assembly, reach out and I will give you a few pointers to help your team build better.


If your project has plastic plumbing boxes in fire rated walls you have a problem. Do you know what it is?  It’s a risk if there is ever a fire. It’s a liability if the project ever gets closely scrutinized.   If you have plumbing boxes in fire rated walls, you need to understand this better. Please read further.

This box, and all others I have seen to date, do not meet the code requirements. You might tell me, “But Sharron I have a submittal for this! My architect and my building official both approved it.” My response? You still have a code violation. The explanation will take a bit and we will be developing a training that explains this in detail. If you want to sign up to be the first to access this training just let us know. If you have a project going on right now that has this issue, you don’t have to wait for the training. We can still help, just fill out the contact page and we will get back to you, or call directly.

send us a note if you want to participate in a training that discusses the challenge with this application even more


PHOTO SEVEN IDENTIFICATION (use photo that is the 4th in the current site- insulated pipe and block wall with red stripe from roughly top center down about ¼-1/3 the photo frame)

This is a red flag issue that the QC team needs to take action on BEFORE the firestop crews come through. These pipes often carry a lot of weight, and if the fiberglass insulation gets crushed it can’t provide the right R value (insulation value). The installers will put a rigid insulation at the hanger and the saddle will displace the weight across the insulation rather than in just in the location of the hanger. If your insulator is only concerned about the R value they may assume two different insulations with the same R value can be firestopped the same way. This is not necessarily true, so you need to know what materials you are dealing with and there is a lot that goes into this.

When you slide the photo to the side, you will learn how to QC this differently.

Problem 1: The saddle is located in the rated wall

                Solution 1: slide the saddle out of the wall and ensure the insulation in the wall conforms with your firestop detail.
                Solution 2: before the pipe is run keep an eye out for the location of the hanger in proximity to the rated walls so the hangers can be relocated and this issue is avoided all together.

Problem 2: The firestop detail that was submitted required
                A) a heavier gauge sleeve
                B) did not allow the sleeve to stand proud of the wall