Good Better Best
If you agree with the argument, I have made this week then let’s talk about a few different ways you can address this to bolster the life safety rating of the assembly.
Good would look like this.
The hole that the toggle bolt runs through would be no larger than it needs to be, the holes are cut clean with a drill that is not pushed through the wall because this can spall the drywall on the other side and that will not only impact the ability of the toggle to hold the apparatus on to the wall but it will ensure that in a fire scenario the wall is degraded even further. Clean holes are going to be very important in keeping the integrity of the wall intact.
Better would look like this.
A sheet metal backer would reinforce the toggle bolt, but it would also keep the holes tight. So, this would be even better.
Best would look like this.
If you used mineral wool in the wall, either 2.5-pound SAFB or 4-pound density would be fine (technically even fiberglass insulation would be acceptable, but I personally would prefer to see mineral wool) . This fire blocking would reduce the thermal transfer from one side of the wall to the other. And therefore, this is the best option in my opinion if you are choosing not to firestop the toggle bolts.
(See the code section below- exception 2 item 2. SOLID is defined in the building code as a material that has a melting point, decomposes, or sublimes at a temperature greater than 68F, so technically fiberglass insulation meets that requirement but if we are really talking best, I say mineral wool)
Now DO NOT take a big ole blanket and cover all small membrane penetrations with this because if you are talking about a horizontal assembly the scenario is very different. That my friends are a topic for another time. I think I have given you a lot to noodle on this week. I would love to hear what you think about this. Remember, this is just one firestop geek’s opinion. You always need to check with your design team and your local building official to see what THEY SAY. They are more than welcome to agree, or to disagree. If they disagree, I would love to hear about it because if I am wrong, I would want to be corrected. If you have questions of other things you would like to know about, I would love to hear from you on that as well.
714.3.2 Membrane Penetrations
Membrane penetrations shall comply with Section 714.3.1. Where walls or partitions are required to have a fire-resistance rating, recessed fixtures shall be installed such that the required fire resistance will not be reduced.
2. Membrane penetrations by listed electrical boxes of any material, provided such boxes have been tested for use in fire-resistance-rated assemblies and are installed in accordance with the instructions included in the listing. The annular space between the wall membrane and the box shall not exceed 1/8 inch (3.2 mm) unless listed otherwise. Such boxes on opposite sides of the wall or partition shall be separated by one of the following:
- By the horizontal distance specified in the listing of the electrical boxes.
- By solid fireblocking in accordance with Section 718.2.1;
- By protecting both boxes with listed putty pads; or
- By other listed materials and methods.