canuck

Hi, I was hoping someone here knew a definite answer to this question or a place I can find one.

Building:
A commercial building 1 story, flat roof, metal deck, structure is steel. The exterior is drywalled and the air/vapour barrier is applied onto the outside of the exterior drywall. The roof is a rubber membrane.

To complete the insulation a spray foam was used on the steel that supports the roof at the top of the walls. The walls are not rated wall on the inside. On the interior the drywall is 3/4" shy of the decking to allow for deflection. This leaves a 3/4" gap of exposed foam.

The foam is Polar Foam 7300

Does this foam need to be fireproofed?

Thanks for any help.

JohnS

If the foam is left exposed in a occupied space that I do believe that it will require some sort of fireproofing cover. if the drywall is applied overtop of the foam that as long as it is fire-rated then you should be good. You can contact CPi - Construction Polymers with such questions and their Building Science department can help answer such questions.

Anti-wingnut

I would think not, because as you say, the walls are not a rated assembly. Two things that concern me are:

1) Flame spread of the exposed foam

2) "Not rated walls on the inside". I have seen details that were rated on one side, and not the other, but have never been even remotely involved in such as structure. Most locations have been residential garages, where the exterior siding has no rating. Is your exterior a rated assembly? This could be the case where you encroach on the property line closer than an arbitrarily defined limit, generally 5'. Such encroachments are common in commercial work. If so, I would think that the rating of the exterior is going to become dragged into the interior