Vertical fire wall continuity with different materials

[eyden]

We are renovating an old warehouse into a commercial building. Two of the walls are on the property line and were not previously fire rated at all. We grabbed an assembly from the GA Fire Resistance Manual to keep the existing framing. 3/4" stucco over 5/8" type X gyp, 2x4 wood studs, 2 layers of 5/8" type X gyp. The building has open web trusses, and in some places we are framing in a ceiling as well. The contractor is claiming that after framing, it will be difficult to get into some spaces between the ceiling framing and trusses to run the drywall up to the roof sheathing with the required screw spacing and asking us for alternatives. It was suggested that that part of the wall be sprayed with intumescent paint instead of the 2 layers of gyp to get the required rating. This raised some red flags for me.

1) CBC 706.6 Vertical Continuity - fire walls shall extend from the foundation to a termination point not less than 30" above both adjacent roofs.
This says nothing about the assembly materials being continuous, so as long as I can maintain 2-hr with the intumescent, can I use that for a section of it?

2) As a fire wall, it needs to be rated from both directions. Will removing the 2 layers of gyp negate the rating on the exterior side, or does that stop at the studs?

3) If it is allowable, how would I transition between the two? Just cap the wall with 2 layers of gyp and overlap the intumescent?

https://imgur.com/PTpUKBo

Thank you

 

[cda]

Not into exterior walls

If existing condition, not sure why has to meet current code.

Box rate around it??

 

[tmurray]

Is it a fire wall or a fire rated wall?

Does the contractor have a listed design for intumescent? We went through this when I started working for my current AHJ. They had never done commercial inspections before and people thought they could just throw some intumescent paint on things and then it good enough.

typically it is the rating that has to be continuous, not the materials themselves. Some strong attention would need to be payed to the interface between different materials to ensure the continuity of the rating in these areas.

 

[eyden]

Not into exterior walls

If existing condition, not sure why has to meet current code.

Box rate around it??

That was our argument too, but the Fire Marshall is making us. It's a cannabis dispensary so they're all extra strict in my area right now.

Do you have an example of box rating?

 

[e hilton]

It's a cannabis dispensary

Pass out samples before the next inspection.

 

[eyden]

Is it a fire wall or a fire rated wall?

Does the contractor have a listed design for intumescent? We went through this when I started working for my current AHJ. They had never done commercial inspections before and people thought they could just throw some intumescent paint on things and then it good enough.

typically it is the rating that has to be continuous, not the materials themselves. Some strong attention would need to be payed to the interface between different materials to ensure the continuity of the rating in these areas.

I'll admit I get a little confused on the difference, but have been considering it a fire wall as it's on the property line.

The contractor does not. He's also of the belief that he can throw some intumescent paint on the wall directly over studs and rockwool, or maybe a layer of gyp or osb that isn't as strict in it's nailing requirements.
Shield Industries has some that I've been looking at: https://shieldindustries.com/wp-content/uploads/2020/04/W-10.pdf

Any thoughts on how that might work? Would it work to add blocking and 2 layers of gyp, effectively capping the rated wall, and then overlap a layer of gyp and spray over that?

https://imgur.com/Muk7moR

 

[Paul Sweet]

A fire wall usually separates 2 buildings, and must be constructed so the construction on either side can collapse without pulling the fire wall down. This just looks like a rated exterior wall.

 

[eyden]

A fire wall usually separates 2 buildings, and must be constructed so the construction on either side can collapse without pulling the fire wall down. This just looks like a rated exterior wall.

Ok. That makes sense. But that doesn't change the continuity requirement as a fire barrier right? From the foundation to the underside of the roof sheathing + the parapet. Can this then be interpreted as a CBC 707.9 Void at intersections situation?

 

[TheCommish]

What are the dimentions of the space, height, and distance to the roof trusses and ceiling framingt?
Is the contractor saying it will be diffculet or just more work than they want to expend?
Howabout core board, H chanel and C track wall, less screws

 

[RLGA]

Ok. That makes sense. But that doesn't change the continuity requirement as a fire barrier right? From the foundation to the underside of the roof sheathing + the parapet. Can this then be interpreted as a CBC 707.9 Void at intersections situation?

It's not a fire barrier, either--it is a fire-resistance-rated exterior wall. The fire protection should extend through the concealed space since the exterior wall requires protection from an interior exposure regardless of fire separation distance. The exterior wall will only need to have a 1-hour rating per Table 602.

 

[eyden]

It's not a fire barrier, either--it is a fire-resistance-rated exterior wall. The fire protection should extend through the concealed space since the exterior wall requires protection from an interior exposure regardless of fire separation distance. The exterior wall will only need to have a 1-hour rating per Table 602.

Hmm. Thanks for bearing with me on this. I was alway taught that a fire-resistance-rated wall had to fall into one of the categories of a fire wall, fire barrier, fire partition, or smoke barrier. Is this wrong?

The occupancy is M and S-1, so still 2-hours. Thinking about it as interior vs exterior exposure is helping. The rating is for the full assembly right? The 2-hr exterior exposure rating doesn't end at the studs (the major structural element)? I can't remove the layers of gyp at the interior and replace them with the intumescent paint unless I can find the full wall assembly allowing that?

 

[RLGA]

Hmm. Thanks for bearing with me on this. I was alway taught that a fire-resistance-rated wall had to fall into one of the categories of a fire wall, fire barrier, fire partition, or smoke barrier. Is this wrong?

The occupancy is M and S-1, so still 2-hours. Thinking about it as interior vs exterior exposure is helping. The rating is for the full assembly right? The 2-hr exterior exposure rating doesn't end at the studs (the major structural element)? I can't remove the layers of gyp at the interior and replace them with the intumescent paint unless I can find the full wall assembly allowing that?

Fire walls, fire barriers, fire partitions, and smoke barriers are fire-resistance-rated assemblies. Fire-resistive wall construction per Table 601 and exterior walls per Table 602 are not assemblies. Assemblies require opening and penetration protection, whereas fire-resistive construction does not, except under some circumstances for exterior walls based on fire separation distance per Section 705.8.

When you said commercial building I assumed Group B. Yes, you are correct, Groups M and S-1 would require a 2-hour exterior wall. Also, the parapet will be required to have a 2-hour rating per Section 705.11.1.

Intumescent paint is not tested for fire resistance per ASTM E119 or UL 263--only intumescent fireproofing is. Intumescent paint is intended to improve a substrate's performance for flame spread and smoke development per ASTM E84. I know of no intumescent fireproofing system suitable for use on wood construction. If you have found one, please let me know.

 

[eyden]

Fire walls, fire barriers, fire partitions, and smoke barriers are fire-resistance-rated assemblies. Fire-resistive wall construction per Table 601 and exterior walls per Table 602 are not assemblies. Assemblies require opening and penetration protection, whereas fire-resistive construction does not, except under some circumstances for exterior walls based on fire separation distance per Section 705.8.

When you said commercial building I assumed Group B. Yes, you are correct, Groups M and S-1 would require a 2-hour exterior wall. Also, the parapet will be required to have a 2-hour rating per Section 705.11.1.

Intumescent paint is not tested for fire resistance per ASTM E119 or UL 263--only intumescent fireproofing is. Intumescent paint is intended to improve a substrate's performance for flame spread and smoke development per ASTM E84. I know of no intumescent fireproofing system suitable for use on wood construction. If you have found one, please let me know.

It looks like my end result is correct, but that I was thinking about assemblies vs construction incorrectly. Thank you for the explanation.

I've been looking at https://shieldindustries.com/product/fireguard-e-84/
It still requires a layer of gypsum though. I keep seeing intumescent fireproofing and intumescent paint used interchangeably on their websites, but I suppose I don't have a preference either way.

 

[RLGA]

It looks like my end result is correct, but that I was thinking about assemblies vs construction incorrectly. Thank you for the explanation.

I've been looking at https://shieldindustries.com/product/fireguard-e-84/
It still requires a layer of gypsum though. I keep seeing intumescent fireproofing and intumescent paint used interchangeably on their websites, but I suppose I don't have a preference either way.

That product (as the name and description indicate) only improves flame spread and smoke development per ASTM E84 and does nothing for fire resistance per ASTM E119 or UL 263. I see they use "fireproofing" in the brief intro on the product webpage (probably by some marketing intern), whereas the detailed description below and the packaging itself are void of that terminology; however, the description does mention "fire-rated wall," which is completely incorrect.