Head of Wall, Fire rated partition

[perezarch]

Is there a head of wall detail or condition that allows a 1 hour fire rated partition to terminate at a 22 gage steel roof deck without concrete fill with Class A roof covering? Florida Building Code. The existing building is Type III-B, no roof fire rating required and the Occupancy is "B", office use....We are providing a 1 hour fire rated wall between office suites.

[Jerry Peck - Codeman]

I'm trying to envision a 22 ga metal roof deck which is flat enough for roofing to be applied to it without having concrete poured on the metal pan roof decking.

I am familiar with metal roof decks of various designs (such as these: https://d-macindustries.com/steel-roof-decks/ ), but a flat metal deck (not 'flat' as in 'level' or 'no/low slope', but as in 'in-plane' without ribs).

With those types of metal pan roof decks, they are topped with concrete.

[perezarch]

[Jerry Peck - Codeman]

So far, the best examples of what, why, and how is here: https://www.iccsafe.org/wp-content/uplo ... Joints.pdf

Scroll down to page 40 (page 41/106

There is also this, which is somewhat applicable to your question as metal buildings have metal roofs, and head of wall joints to those metal roofs would be similar to your question: https://www.awci.org/media-archives/con ... resistance

[Jerry Peck - Codeman]

I had a similar condition today at a project here in Florida, except instead of being the head of wall terminating at an unrated roof, it was the end of wall terminating to an unrated wall (in this case an unrated exterior wall) ... but the same question: what needs to be done to terminate the rated wall at an unrated wall?

The same scenario would apply to terminating the head of the wall to an unrated roof.

Let's first address the unrated wall. What could an unrated wall wall be? Well, to start off with a rather ridiculous and exaggerated example ... the unrated wall could be 'parchment paper'.

Okay, I agree, there is no way that 'parchment paper' would pass muster as an exterior wall under typical building codes, but the example is given to first understand that the unrated wall (or roof) is essentially deemed to 'burn through' ... it is not rated to survive a minimum length of time, it is expected to 'burn through' ... thus my use of 'parchment paper' as that would definitely 'burn through' ... and burn through rather quickly.

Okay, so let's move on to a more realistic wall material - structural wood panels.

Thus, for the example, the rated wall will be terminating at a structural wood panel unrated wall. The rated wall is rated for the time the wall offers protection from either side to the other side and that it will stay in place without allowing the fire to pass through to the other side.

With that in mind, the termination of the rated wall at the structural wood panel unrated wall needs to keep the fire on either side of the rated wall from going through to the other side of the rated wall.

To accomplish that, one needs to consider the surface of the unrated wall (at the point where the rated wall terminates to it) as being rated to the same rating as the rated wall and that the joint (termination) where the actual rated wall meets the unrated wall needs to be treated the same as one rated wall meeting another rated wall of the same rating.

In this case, the exterior wall is continuous and the interior rated wall terminates at the exterior wall (like a 'T' joint) and the joint would likely be fire-caulked sufficiently to maintain the rating of the rated wall.

The fire on one side of the rated wall will be impinging on the unrated wall to the point that the unrated wall burns through, while at the same time, the fire does not go through the joint at the end of the rated wall until the unrated wall 'burns through'.

Going back to your head of wall question, the head of wall joint would be treated the same for an unrated roof deck as it would be treated for a rated roof deck with the same rating as the rated wall - with the purpose to keep the fire on one side of the rated wall from getting past the head of the wall to the other side of the rated wall through any deformations in the metal pan roof ... keep the fire on one side of the rated wall until the unrated roof deck fails.

The result being that the same head of wall details for rated walls to rated roof decks are used for the rated wall to the unrated roof deck.

That would be because an unrated roof deck would be presumed to be allowed to 'burn through' on either side of the rated wall, while at the same time the joint of the rated wall at the unrated roof deck is presumed to not allow the fire to go from one side of the rated wall through the joint at the unrated roof deck to the other side of the rated wall.