Do you have PEX on your project? Make sure this mistake isn’t happening
Welcome back to the series where we talk about “stuff we see wrong in the field.” This blog is going to discuss a few challenges we have found with PEX on your project in wood-framed buildings. If you are working on a concrete project that is using PEX on your project, you should still read this just in case you are making the same mistake. We hope it is useful.
Here is our field condition:
The plumber drilled a hole through the two by fours sitting on the plywood floor to frame the new wall. The hole is less than ½” larger than the pex line they are running. This gives them just enough space for the bracket the plumber is using. In the field, they call them mickey mouse ears. I’m not sure what they call them in your area but here is an example of one.
The firestop installer simply smeared firestop around the pex on your project line and covered the mickey mouse ears. It wasn’t until we did destructive testing that we discovered the problem. If you’re an inspector on a project without special inspection requirements, visit the site before installing the firestop to check for these materials. Should you find them, consider asking a few questions. For additional assistance, feel free to give us a call.
The problem:
The mickey mouse ears use up all the annular space that you need for the installation of the firestop material. With plastic pipes you typically need to have an intumescent firestop material. This is one that is capable of expanding to fill the void created when the plastic pipe melts away during a fire. The intumescent material can close down the opening and prevent the passage of fire.
Intumescent materials act like most things in nature. That is to say that they move in the area of least resistance. If the material is on top of the two by four and next to the PEX pipe, it will expand into the area with the least resistance. This will be away from the pipe.
For this reason, the intumescent material needs to be forced into the opening. This ensures that the two by four, the concrete, or the drywall can contain the sealant as it expands. The sealant is pushed into the center of the opening. This process allows the material to close off the opening as the plastic pipe softens during a fire. As the pipe yields to the expanding intumescent sealant, the gap is effectively sealed.
This is also why a plastic pipe touching the side of the opening needs a bead of sealant. This bead builds up along the edge of the penetrant and against the rated assembly.
A detail specifying 0-1” annular space doesn’t mean you can have zero space around the entire opening. If this is allowed the detail should say “continual point contact” and few details do.
The solution:
There are a few ways to handle this. One would be to not use the Mickey Mouse ears. Another approach would be to install the firestop first. Then, as you push the bracket into place, you should force the sealant into the opening. Consequently, inspection may become difficult. Therefore, ensuring proper sealant depth during installation becomes imperative.
If you run into this issue, let us know how you handle it.
Thanks for taking the time to read this. We hope you found it valuable. If you did, please leave comments and let us know what other topics you would like to see us address in future blogs. Share this with anyone who can benefit and keep learning. Check back for more in this blog series as we discuss other field issues we encounter.