How does the electrician know which walls are fire rated?

In buildings constructed prior to the 2015 IBC adoption, fire rated walls will be harder to spot for an electrician installing boxes or running cables and conduits. Only someone familiar with wall construction and occupancy types will know which walls of an older building are required to be fire-resistance rated.

In 2015, Section 703.7 (now 703.5) was added to require special marking on fire walls, fire barriers, fire partitions, smoke barriers and smoke partitions that are required to have protected openings or penetrations. The intent is to alert those about to penetrate rated construction so that the fire-resistive rating will not be compromised by the work that is about to occur.

For older buildings with rated walls that are not marked like in the image, when making a penetration for new wiring methods, be sure to look for specific indicators of rated walls such as the wall being built from the floor all the way up to the roof decking, multiple layers of sheetrock on the walls with staggered joints, fire caulking at existing penetrations and the like.

IBC Section 703.5 states the following:

IBC 703.5 Marking and identification. Where there is an accessible concealed floor, floor-ceiling or attic space, fire walls, fire barriers, fire partitions, smoke barriers and smoke partitions or any other wall required to have protected openings or penetrations shall be effectively and permanently identified with signs or stenciling in the concealed space. Such identification shall:

1. Be located within 15 feet (4572 mm) of the end of each wall and at intervals not exceeding 30 feet (9144 mm) measured horizontally along the wall or partition.
2. Include lettering not less than 3 inches (76 mm) in height with a minimum 3/8-inch (9.5 mm) stroke in a contrasting color incorporating the suggested wording, “FIRE AND/OR SMOKE BARRIER— PROTECT ALL OPENINGS,” or other wording.