Damper rating

[DwightB]

2007 Florida Mechanical: Situation: A 3 story building, Mixed occupancy: A-3 and E (church and school). Type 1B construction. Table 601 requires 3 hour rated exterior or interior bearing walls. The walls are 9" thick concrete tilt-up walls, similar to UL926, which requires only a minimum of 6" precast concrete wall for 4 hour rating. At 9' thickness (50% over) we could conceivable be up to 6 hour rating with this if thickness and ratings were on a linear scale.

The question: In locations where this wall happens to separate an exit corridor from another function (class or office, for example), is the damper required for a duct penetration as required for the corridor (1 hour), as required for the bearing wall (3 hour), as for the rating claimed by the UL rating (4 hour) on the plans for this wall, or as the rating provided by the built unit (possibly 6 hour)?

If the answer is "as required for the bearing wall", then I assume it can also be reduced to 2hr per footnote "b" on the upper floor.

Problem: the Mechanical inspector is saying "3 hour wall = damper rated for 3hr wall"

 

[mjesse]

716.3.1 Fire protection rating.

Fire dampers shall have the minimum fire protection rating specified in Table 716.3.1 for the type of penetration.

TABLE 716.3.1 FIRE DAMPER RATING

[TABLE=align: center]

[TR]

[TD]TYPE OF

PENETRATION

[/TD]

[TD]MINIMUM DAMPER RATING

(hours)

[/TD]

[/TR]

[TR]

[TD]Less than 3-hour fire-resistance-rated assemblies

[/TD]

[TD]1.5

[/TD]

[/TR]

[TR]

[TD]3-hour or greater fire-resistance-rated assemblies

[/TD]

[TD]3

[/TD]

[/TR]

[/TABLE]



From 2006 IBC

mj

 

[steveray]

It should be based on the required and documented rating of the wall assembly....if it needs to be 3 is 4 it could be based on 3hr but should be documented as a 3 hr assembly....based on mjesses post it shouldn't matter in this situation, if we were talking about 3 vs 2 hrs it might be more of a problem.....An improper damper might derate a wall.....

 

[AegisFPE]

Table 601 addresses structural integrity, not compartmentalization. Similar to how a wall opening need not be rated in a Type V-A bearing wall, the same should hold true for a Type I building.

The purpose of opening protectives is compartmentalization per Chapter 7. Section 713.3 specifies which assemblies need protection for penetrations and 716.5 thru 716.5.5 addresses where fire & smoke dampers are required. There is no specific reference to protection of openings in Chapter 7 for openings in assemblies only required by Table 601.

 

[DwightB]

So, if the requirement is for a 3 hour exterior bearing wall and steveray says an opening may derate the wall, why can we punch them full of windows where there is no separation factor? I'm thinking the 3 hours is for protection of the bearing capacity (i.e. "load bearing walls") and not for separation. Where I have an interior wall and the bearing requirement is 3 hour (which is provided by the concrete wall), but the separation requirement is 1 hour (corridor), I think the damper should only be 45 min.

 

[gbhammer]

:agree

So, if the requirement is for a 3 hour exterior bearing wall and steveray says an opening may derate the wall, why can we punch them full of windows where there is no separation factor? I'm thinking the 3 hours is for protection of the bearing capacity (i.e. "load bearing walls") and not for separation. Where I have an interior wall and the bearing requirement is 3 hour (which is provided by the concrete wall), but the separation requirement is 1 hour (corridor), I think the damper should only be 45 min.

I believe your correct.

 

[Builder Bob]

Let's take the code apart piece by piece....

T601 is for structural fire protection values......

3 hours required.

Can I have a open sided steel column tower used for obervation purposes to be unlimited in height and still meet the three hour rating on the steel columns (this is a hypothetical situation - bear with me as I know there are also rules that allow reductions, etc.)

Now take the same design and infill the exterior parts of non-load bearing portions of the wall ...... Type I T 601 with a fire seperation distance of 30 feet..... this can be non-rated----

Non-load bearing interior partitions are not required to be fire rated by T601.

As long as the structural components are designed to support the loads above it for three hours, it shouldn't matter how I construct the rest of the wall, mechancial, electrical, etc. unless another povision has a requirement for this are to be protected..such as a fire rated corridor -

At which time the fire protection rating should be what is required for that application -

Now the real world application of the question posed -

The senario presented does not provide enough infomation -

If the structural designer and a fire protection engineer agree that the openings in the walls for mechancial, plumbing, and HVAC do not affect the load bearing walls ability to maintain the three hour fire resistant rating for three hours, the opening protective is only required to be that as for a typical fire rated corridor.

If the documentation or determination has not been made by the proper design professionals-- The Mechancial Inspector is correct is his requirement.

This is JMHO --- Others may vary greatly.

 

[AegisFPE]

From a compartmentalization perspective, I concur with Steve. But, with regard to wall assemblies in Table 601, an unprotected opening shouldn't necessarily derate the structural fire endurance of the assembly, though as Bob suggests, it should be evaluated.

There is no requirement that a bearing wall be continuous from exterior wall to exterior wall. Therefore, a bearing wall per Table 601 cannot be relied upon for compartmentalization, unless it is also constructed as a fire barrier or some other IBC-prescribed assembly.

Consider an opening occurring between beams supported by the wall, so perhaps in that specific location can be considered to occur in a non-bearing wall. In such case, Table 601 requires 0 rating. For ease of construction, it all looks the same, but there is nothing in Section 601 to require the fire-resistance to be maintained for the length of the wall.

Say there's another opening right next to that one, directly under a supported beam. Should that one be protected? Table 601 says bearing walls require fire-resistance ratings. But the one right next to it in a non-bearing wall needed no protection. Further, let's say the assembly is not even continuous to the surrounding walls of the room, it's just a wall segment in a large room, so the space on both sides of this bearing wall is a common atmosphere.

Sounds like you're on the right track Dwight.

 

[DwightB]

BuilderBob: I'm the design professional on this, and the structural engineer has accounted for ductwork openings, so there is no issue there. The issue comes down to protection of the exit corridor, the 1 hour protected path.

 

[Builder Bob]

I am sure that it was taken into account by the design professional --- sometimes the problem is that this isn't communicated to the code enforcement people.

My father explained something to me along time ago ---- (He had a PHD in education)

Son, it doesn't matter how many degrees or letters you can place after your name if you can't break it down into terms that the simple lay person can understand.

In instructional education, communication is described as having an idea communicated, recieving feedback that the idea has been communicated(Acknowledged),

Then re-confirming that the idea has been communicated and understood.

Otherwise known as the tell them two times, ask 'em if they understood, and then tell 'em again the idea and that they understood the idea........

Just an Old country boy who has been in alot of different seats........

Most of the problems arise when people fail to communicate and discuss ideas/opinions.

 

[klarenbeek]

BB is absolutely right on this. As a mechanical only inspector, I've run into similar situations. Initially, all I know is that I have a rated wall, and duct openings in a rated wall need to be protected to maintain the rating. It's only after further coversations with the design professional and framing inspector that I find out the wall is only rated for bearing and the hvac openings have been accounted for and fire dampers are needed only if the wall is also a separation wall. I've seen wood frame walls that need a 1 hour bearing rating but no separation. after hashing that out, all tha was needed was to line the inside of the duct penetration with the proper drywall to maintain the protection of the wall structure itself.