Membrane Penetration Firestop Part One

Membrane penetrations refer to firestop applications that breach only one side of a rated assembly, and they often receive poor reviews. This applies to wall penetrations. Moreover, this issue is even more critical for floor penetrations, and as noted in our blog, we frequently present information in multi-part series to ensure a thorough understanding. This topic will be no different. We will start with two documents: one from UL and one from the IFC. We will build on these to help you understand what to look for on job sites. This doesn’t matter if you are an AHJ part of a QA/QC team or a special inspector. You need to know the information in this series to help increase the level of life safety and reduce liability. Therefore, please read this information carefully and challenge yourself to apply it effectively to your projects.

We will start you on this UL document.

Here are a few key takeaways-

• Look for the UL logo
  • Check that the product is approved for use in the rated floor, wall, or ceiling where you plan to install it.
  • If you don’t find it, check whether the box is tested for use in a fire-rated assembly. You can’t just throw a putty pad on the non-rated boxes to fix the problem. It’s not that simple.

• Check the size of the boxes. A UL-listed box must be small enough to avoid needing a putty pad. This requirement applies regardless of the box’s proximity to other boxes. Metal boxes cannot exceed 16 square inches. Plastic boxes may vary depending on the manufacturer and the testing standards. Check the paperwork to determine the specific requirements.

• When reviewing the firestop detail, pay close attention to whether the application requires specific conditions.

• a metal cover plate 

• Place a ball of putty inside the box. I rarely see this done despite the requirement, and people often skip it without facing any repercussions.

• don’t assume that you can throw a putty pad on any sized box. Refer to the CLIV (the tested detail) for the limitations

• depth of box is a big deal. We will get into this in a future discussion, but if you recall our conversation about shaft wall assemblies it is related too that. If you didn’t see that you can review here. 

• Ensure the box is rated for the specific wall, floor, or ceiling where you will install it. A box rated for walls is also suitable for ceilings and floors. You can use it in any of these applications.