NM above 29 gauge steel

[survivaljgb81]

What is the minimum thickness of steel for a 15 minute fire rating as required by code? Example commercial garage with ribbed steel 29 gauge for ceiling. Would it have a minimum of 15 minutes?

 

[GoldDigger]

IMHO it depends in part on whether there are any combustible materials in contact with either side of the roof. Sheet steel, regardless of thickness will conduct heat very well and can easily get red hot on the far side.
My other concern is what the temperature exposure is? Hot enough to melt the steel and allow flame through? That depends on the fuels present, among other things.

 

[petersonra]

IMHO it depends in part on whether there are any combustible materials in contact with either side of the roof. Sheet steel, regardless of thickness will conduct heat very well and can easily get red hot on the far side.
My other concern is what the temperature exposure is? Hot enough to melt the steel and allow flame through? That depends on the fuels present, among other things.

I don't think it matters what any of us think. The building codes define what The fire rating is for the various types of structures. The building codes and UL.