Dear Architect- Why don’t your specifications require L ratings?

One of my pet peeves is people who use code verbiage WRONG.  A fire wall is not the same as a fire RATED wall.  Watch this video and you will see what I mean. The FIRE WALL saved the lives of the fire fighters in that video, well, the fire wall and some damn good teamwork. A standard fire RATED wall would not be expected to perform the same way as a FIRE WALL which runs from the lowest level up to or through the roof. The fire fighters know that the parapet is a FIRE WALL and that it should be built such that there can be complete structural collapse on the one side and the other side of the wall is safe from fire or safe from collapse.


These FIRE WALLS are used by architects when they have a building with an area larger than what the code allows. This is effectively making one building into two or more buildings, or segments of a building that are connected by this rugged structural wall.

So what about fire barriers and smoke barriers?  These are NOT the same either.

Did you know that a fire barrier should have an F rating? more on that here.  Yeah, well a smoke barrier is required to have a one hour F rating too. That means that all the penetrations through a fire barrier or a smoke barrier are also required to have an F rating that matches the F rating of the wall?  This is hopefully no surprise to you at this point.  This however this next point might be.

Did you know that joint or a penetration in a smoke barrier has to pass one additional test that a fire barrier DOESN’T have to pass.  It is an L rating and Engineering Toolbox explains it here.  So this means when you are reviewing the firestop submittals you have to know where your smoke barriers are, what rated assemblies they connect to and what penetrates them. First you have to identify these items, then  you have to ensure that the firestop details you have received are capable of meeting this code required test.  When I say YOU, I am talking to all of you- the architect, building official, GC, firestop installer or special inspector. If the trades are self performing their own firestop, then I am talking to each of the trades as well.

Do you know, if you project has smoke barriers?  If you have them please check your firestop submittals to see if your details cover this code requirement.

If you are working in a hospital, pay particular attention because smoke barriers may be a requirement to help reduce the nosocomial infection rates.  You know the person who goes into the hospital with a broken arm and leaves with a cast and the worst flu of their life. That is a remedial explanation of nosocomial infection.  Before you think its not a big deal, you should know that nosocomial infections are linked to the death of  as many as 6 children and the subsequent 2019 closure of Seattle Children’s Hospital, so it is serious business.

L ratings are also important in clean room environments or rooms with FM200 or other similar fire suppression system where room volume is critical tot he life safety measures.

If you have any questions, feel free to give us a call. We are happy to help if we are able.