The Building Code defines unprotected opening (as apply to exposing building face) as “a doorway, window… or any part of a wall forming part of the exposing building face that has a fire resistance rating less than that required for the exposing building face”.
Article 3.2.3.13. for Protection of Exit Facilities refers to ‘openings’ and not the defined unprotected openings. It seems as though there is a varying of interpretation on the difference.
My question is: Should exterior walls be protected with a fire resistance rating (similar to how the requirement applies for spatial separations) for the locations described in Article 3.2.3.13.
3 Responses
Good question! And one I’ve never considered before. I would think that yes walls should be considered unprotected openings should be protected similar to windows, doors, etc. If you read 3.2.3.14.(2) it says, “The exterior wall of each fire compartment […] shall have a fire-resistance rating not less than that required for the interior vertical fire separation between the fire compartment and the remainder of the building.” But the entire portion of the adjacent exterior wall(s) don’t need to be protected, only the areas that fall within those limits determined by the equation in Sentence (1). I haven’t gone through the Code in detail and verified this but I’m not sure this situation would ever exist, at least not in Part 3 buildings. The only situation I could see it being an issue is if, for example, you had an enclosed exit stairwell with a 2h rating and an adjacent exterior wall less than 135 degrees with a FRR less than 1.5 hours. Although this is a situation that could occur, if you continue to Sentence (3) of 3.2.3.14. it says, “Sentence (1) does not apply to unprotected openings of fire compartments within a building that is sprinklered.” Again, I haven’t verified this but I think any building that would require a 2h exit facility will definitely be sprinklered. But what if the exit facility only requires a 1h fire separation? Then 3.2.3.13. says any “openings” within the distances described in Sentence (1) must be protected according to Sentence (4) which includes ‘closures’. Closures don’t need to have the same rating as the the component within which they exist so for a 1h exit stair, anything in it or near it will need a 45 minute rating as per 3.1.8.4. If we look at Table 3.2.3.7. we see that unless the allowable UPO’s is greater than 100%, no walls can ever have a FRR less than 45 minutes so inherently, all exterior walls will already have a 45-minute rating.
Thanks for the response Nelson!
That’s interesting you note about all exterior walls needing a 45 min rating. I have always interpreted that at 100% UPO, the building face did not require an FRR. Because of that, in my experience I have come across a lot of scenarios where the exterior walls were unrated.
I’m going to have to do some digging now on the exterior wall ratings when 100% UPO are permitted!
Hi Kelsey, you’re right but I mention that caveat in my last sentence (“…unless the allowable UPO’s is greater than 100%…). Admittedly, there’s probably a lot of cases in which the exterior wall of a building has no limits on UPO’s and, therefore, needs no FRR but even in that case, it just brings you back to 3.2.3.14.(2) which makes you apply that FRR to the portions of wall that are within the distance prescribed in the Sentence 1 formula. Make sense?