Intumescent paint instead of non-com behind hood

[Sifu]

Received a T/I for an A2 in a VB building. They didn't specify the wall construction behind the a new hood being placed on the existing demising wall. I assumed it was wood, but you never know. I asked for verification of wall construction behind the hood. I guess the architect didn't know the wall was wood framed...so the response was to strip the wall and spray the wood studs with intumescent paint. Anyone heard of or accepted this before?

 

[mtlogcabin]

We require them to strip the wall and replace the wood studs with metal studs where the hood is located.

 

[classicT]

I would not accept intumescent for this use.

 

[Sifu]

Same here, I have always asked for metal studs, and that is what I expected to get back. I feel like this is a throw it against the wall to see if it sticks situation....then they will complain when it causes a delay. Seems way more problematic to use the intumescent paint and a special inspector than to just replace the studs.

 

[fatboy]

I would not accept it either, reframe w/metal studs.

 

[BN4537]

Probably cheaper to reframe with metal studs too...

 

[e hilton]

Could you overlay the wall with a sheet of stainless?

 

[steveray]

Intumescent gives a fire rating (just like drywall)...it does not make something non-combustible...Big negative Woodchuck!

 

[TheCommish]

Could you overlay the wall with a sheet of stainless?

SS does not make the wood non combustible

 

[e hilton]

Sheetrock does not make wood noncombustible, but it provides a layer of fire protection for the wood.

 

[steveray]

Sheetrock does not make wood noncombustible, but it provides a layer of fire protection for the wood.

Yes...but also conducts heat and would not satisfy the code here either....If it says non-combustible finish, that is one thing, non-combustible construction is another...

 

[e hilton]

.If it says non-combustible finish, that is one thing, non-combustible construction is another...

good point.

 

[mtlogcabin]

My understanding is gypsum board cannot pass the test and that is why the code specifically states you can use gypsum board on non-combustible framing with a minimum 3" clearance

506.3.6 Grease duct clearances.
Where enclosures are not required, grease duct systems and exhaust equipment serving a Type I hood shall have a clearance to combustible construction of not less than 18 inches (457 mm), and shall have a clearance to noncombustible construction and gypsum wallboard attached to noncombustible structures of not less than 3 inches (76 mm).

2018 IMC
NONCOMBUSTIBLE MATERIALS. Materials that, when tested in accordance with ASTM E 136, have not fewer than three of four specimens tested meeting all of the following criteria:

1. The recorded temperature of the surface and interior thermocouples shall not at any time during the test rise more than 54ºF (30ºC) above the furnace temperature at the beginning of the test.

2. There shall not be flaming from the specimen after the first 30 seconds.

3. If the weight loss of the specimen during testing exceeds 50 percent, the recorded temperature of the surface and interior thermocouples shall not at any time during the test rise above the furnace air temperature at the beginning of the test, and there shall not be flaming of the specimen.