FRR vs Temperature rise limits

[Plumb-bob]

I am confused!


The tests referred to in 9.10.3.1 are regarding FRR, not temp. rise limitations.

Is it trying to say that if the building has a LD of more than 1.2m there is no FRR required for the exterior walls? If so, this would contradict 9.10.14.5, which shows a minimum 45min FRR for all exterior walls:



When I go to 3.1.7.2 for clarification, I get more confused.

 

[tmurray]

(2) is strictly referring to requirements for temperature rise limits on the assembly. It does not modify the requirements for the hourly rating.

There are requirements related to temperature rise in ULC-S101 for the assembly to achieve an hourly rating. This is just indicating that the temperature rise doesn't have to be a restraining factor if other measures are taken to deal with temperature rise. There would be no impact on assemblies under the Part 9 tables or Appendix D.

 

[Paul Sweet]

Temperature rise limitations are to prevent walls from getting hot enough in a fire to set nearby combustibles on fire. Some assemblies might reach this temperature before they fail structurally. If so, these assemblies should have 2 ratings - one for temperature and one for structural failure.

 

[Plumb-bob]

(2) is strictly referring to requirements for temperature rise limits on the assembly. It does not modify the requirements for the hourly rating.

There are requirements related to temperature rise in ULC-S101 for the assembly to achieve an hourly rating. This is just indicating that the temperature rise doesn't have to be a restraining factor if other measures are taken to deal with temperature rise. There would be no impact on assemblies under the Part 9 tables or Appendix D.

As I thought, thanks.

 

[Plumb-bob]

Temperature rise limitations are to prevent walls from getting hot enough in a fire to set nearby combustibles on fire. Some assemblies might reach this temperature before they fail structurally. If so, these assemblies should have 2 ratings - one for temperature and one for structural failure.

Thanks for the clarification

 

[Inspector Gadget]

Remember that the exterior fire-rated assemblies are different from others in that you only require FR drywall on ONE side of the assembly.... that's the critical takeaway....

 

[Plumb-bob]

Remember that the exterior fire-rated assemblies are different from others in that you only require FR drywall on ONE side of the assembly.... that's the critical takeaway....

I respectfully disagree. An exterior assembly is rated for exposure from the interior, but the assembly may require exterior layers of gypsum. Such as for many of the assemblies found in the Pt9 fire and sound resistance tables.

 

[Inspector Gadget]

I respectfully disagree. An exterior assembly is rated for exposure from the interior, but the assembly may require exterior layers of gypsum. Such as for many of the assemblies found in the Pt9 fire and sound resistance tables.

Looked at the BCBC part 9 assemblies. EWx (Exterior wall assemblies) in BCBC is same as NBC - f/r drywall on the interior only. This is consistent with 9.10.3.3(2) which states that exterior walls need only be rated for exposure to the interior.

The Part 9 illustrated guide kinda explains this better than Code.

 

[Plumb-bob]

Looked at the BCBC part 9 assemblies. EWx (Exterior wall assemblies) in BCBC is same as NBC - f/r drywall on the interior only. This is consistent with 9.10.3.3(2) which states that exterior walls need only be rated for exposure to the interior.

The Part 9 illustrated guide kinda explains this better than Code.
View attachment 13936

I get the exposure from the interior. But the assembly may need layers to the exterior. Look at the Pt9 fire and sound tables, and the notes at the end:

 

[tmurray]

It depends if you are doing a listed system or a component additive method.

Listed: provide everything in the sandwich
Component additive: You don't get time added for things on the "outside" of the framing