Exterior Wall Fire Ratings Demystified
Figuring out the required fire rating of an exterior wall can be a bit tricky. A number of sections of the International Building Code¹ (IBC) govern fire resistance requirements for exterior walls, and the appropriate fire rating for an exterior wall is often based on a multitude of factors such as building construction type, fire separation distance, occupancy group, and whether or not the wall itself is load bearing.
So where do we start?
Well, when it comes to fire resistance ratings of wall assemblies, Chapter 7 is always a good place to jump in, and particularly relevant in our case is Section 705 which pertains to exterior walls. Section 705.5 addresses fire resistance ratings and largely redirects to Tables 601 and 602. Importantly, 705.5 also includes some stipulations about whether an exterior wall must be rated from the inside only or from both sides. We’ll come back to that in just a moment. Our first step is to determine the wall’s fire rating by referencing the two tables in Chapter 6.
Table 601 applies to both interior and exterior walls while Table 602 applies to exterior walls only. Since both Tables 601 and 602 specify fire resistance ratings for exterior walls, both must be consulted and the higher fire rating of the two will govern (as directed by Table 601 Footnote e and Table 602 Footnote a).
