Throughout a construction project, the electrical foreman is responsible for the installation of listed firestopping assemblies for electrical items that may breach a fire-resistance rated barrier – a shaft, wall, or floor. Below are some tips for electrical foreman to be aware during construction projects.
Items that Penetrate Shaft Wall Assemblies
As discussed in our blog titled “Firestopping Sequencing Shaftwall Inspections”, items such as electrical metallic tubing (EMT), metal clad cables (MC), and similar that penetrate a shaft wall assembly typically require two rounds of visual and destructive inspections. Note that this only occurs when a firestopping assembly specifies that the penetrating item must be sealed at both layers. It is imperative that any firestopping at the shaft coreboard layer is installed and inspected prior to installation of the outer gypsum layer (which requires additional coordination with the drywall installer) to avoid opening of walls or rework.
Open Ended Conduits
Metallic or non-metallic electrical sleeves or open-ended conduit may penetrate a rated wall. Firestopping assemblies typically specify that after a wire or cable is run through the open end of the conduit or sleeve, the open end must be sealed to complete the installation. Due to the electrical sequencing on the project, the conduit or wire sleeve itself may be firestopped at the fire-resistance rated wall, however, wires and cables may not be run until later stages in the project. These incomplete installations can often be overlooked as the project nears completion. Additionally, firestopping inside the conduit or sleeve is often removed or damaged to run late-stage wiring, such as data cables or controls, and needs to be repaired.
A membrane penetration is a type of penetration where an item goes through only one side of a floor-ceiling, roof-ceiling or wall assembly, and is firestopped where it passes through the breach. If a membrane penetration were to pass through a fire-resistance rated assembly, it is required to be protected by a listed firestopping assembly just as a penetration through the full (both sides) fire-resistance rated substrate would. Typically, a different listed system is required for membrane penetrations than through-penetrations, even though the installation methodology is generally the same.
Electrical Box Firestopping
Membrane penetrations by electrical boxes may not require a firestopping assembly if they (1) have been tested for use in a fire resistance rated assembly and are installed per their listing or (2) they meet all of the following conditions (IBC 2015 714.3.2):
- The electrical box area does not exceed 16 square inches;
- The aggregate area of openings through membrane does not exceed 100 square inches in any 100 square feet of wall area; The annular space between the wall membrane and the box does not exceed 1/8”; and
- If located on opposite sides of the wall, electrical boxes are separated by 24 inches in different stud cavities.
If these conditions are not satisfied, additional insulation, fireblocking, or listed firestop assemblies arranged per IBC Section 714.3.2 need to be added to achieve compliance with the code.
Potential products that may be permitted for use of firestopping electrical boxes, depending on the specific firestopping assembly used, include firestop putty pads, firestop box inserts, firestop cover plate gaskets and endothermic mats.
The electrical trades often have the greatest variety of firestopping installations on a project, and as such, bear the greatest burden in managing installations. Careful attention paid to the firestopping systems in use and how they are being constructed in the field can streamline the inspection process and reduce or eliminate rework and delayed timelines.