Firestop in Shafts is Often Done Wrong, so Someone Asked, “How do We do it Right?” (part 2)

Okay, so I am hoping that in this last week you have walked around your projects that have plastic pipe and identified the sizes of plastic pipes you have on your jobsites. What type of plastic they are, if they are solid or cellular core, if they are open or vented and that you have firestop submittals for each and every one of your field applications whether they are going through a shaft or not.  I know our discussion is about shafts but the information I am sharing is not restricted to shaft wall assemblies.


Now we are going to look at what the firestop detail tells us we need to verify when we do the field inspection.  Here is the link to the detail, so you can follow along with

WL 2217

At this point you will have already verified that field installation conforms with everything we discussed in the last blog post and everything we discussed above.

The first step of the installation comes with the plastic pipe coming through the shaft liner.  Pay particular attention to this because its going to be tricky.


3B says that the collar needs to be friction fit. This means that if the outside diameter (OD) of the collar is 5” then the hole needs to be 5” and the collar needs to slide into the opening touching the cut edge of the drywall. If this is not cut tight, if the person with the drywall saw made jagged cuts, then it doesn’t conform with this detail.


But wait that is not the only issue here.  This detail requires the collar be secured to the shaft liner with toggle bolts.  If that is the case then those are the only types of anchors that can be used.  This means that drywall screws are NOT acceptable.  I could side bar for a while on why and I will get to that another time, but for now just know it needs to be mechanically fastened and drywall screws are not considered mechanical fastening.


Did you notice that there is another requirement?  The anchors need to include a ¾” washer.  Other details may call for 1” or even 1-1/4” washers.  If these are not used then there is a risk that the anchors can pull out of the wall as the intumescent material expands.  There will be a great deal of potential for movement and pressure applied on this collar so it needs to be secured strongly to the wall and all of these are requirements, not suggestions.



No joke: I was doing a training session with a field installer team and I went into a local Home Depot and asked where they had their fender washers. They guy looked me straight in the eye and said, “Ma’am we don’t sell car parts here at Home Depot. “  I walked away in shock and asked the next person, “Where are your nuts and bolts?”


Okay, so back to our firestop detail:

You may have noticed that there is no requirement for sealant on the shaft liner.  That is because the collar is friction fit into the opening and this will limit any air movement that would be stopped by sealant.


The outer layer of drywall will allow for a gap, but how much of a gap?  The detail says that the maximum size of the opening in the outer layers shall be 5”. That annular space shall be filled with FS One which is an intumescent firestop sealant. Then the collar shall be installed on the outside of the outer layer of the shaft wall assembly with the same anchor tabs, toggle bolts and washers.  One thing we didn’t mention is that the collar comes with anchor hooks and you will need to use 2 hooks for pipes 1-1/2” to 2” and three anchor hooks for pipes three and four inches in diameter.


As you can see, there is a LOT to look at!  There are a lot of steps to this as well. Now imagine how to do this same type of installation on a block or concrete wall. Clearly you cant, so how will you address that type of shaft wall assembly?  Check in next week and we will go over this and introduce you to a great problems solving product.  If your contractors forgot to install the collar on the shaft liner side, you may be able to use this solution as long as the hole in the shaft liner is not a mess.


Remember, if you want us to take a look at your project to be sure you are on the right track, we are offering a complimentary review through the month of July.  Contact us for more information.