2 hour fire separation needed

[Justin Damore]

Please Help! I need a solution to this problem. I need to create a 2 hour fire separation between a lower level and the space above. The current floor / ceiling assembly is 3/4" T&G over bar joists. Bar joists measure 9.5" tall, x 3.25" wide on 16" centers... The owner's goal is create the fire separation on the bottom side of the assembly only with dry wall layers but everything i find, calls for a layer of concrete on the top..

How can we qualify a 2 hr separation on the underside only?

An alternative option to qualify would be 3/4" layer of gypcrete on top of the t&g and intumescent paint on the bottom side leaving the joists exposed underneath..

Please help.. Ive search every assemble on line i can find

 

[DaveAtkins]

I suspect the problem is the assembly needs to be protected from both sides--below AND above.

I would go with the gypcrete. It is done quite often in this type of construction, with the added benefit of a level floor.

DaveAtkins

 

[dik]

Can you spray the OWSJ with firespray to give you the 2 hours? It may be a matter of looking up the UL listing for floor construction.

Dik

 

[Justin Damore]

Flame Off shows specs to provide 2 hour protection on the metal bar joists but only one hour on the T&G. So i need 1 more hour to add to the wood. My initial thought was to got with a 3/4 inch layer of guy-crete on top of the wood. ( it seems the code official is willing to accept a calculated formula) But, i don't have any data to support the gypcrete protection time. Nor do i have any data to support a drywall burn time by itself as i could use flame off plus drywall, leaving the whole top side as is, which is the desired result.