Thread: R317 in the IRC book

I did an inspection on this 4 year old duplex where fire rated drywall was installed in the attic separating the two units. I went into the garage attic and the same drywall was installed in the same way (all the way to the roof). Then where the over the attic space stopped and the space where to roof sheathing began (separation of the garage space and house attic space) there was no drywall separating the two units. I can literally go up into the attic from the garage at one unit and walk around the firewall and enter the next unit's garage attic space. Is this installation correct and if so, is it because of the wood sheathing is separating the garage attic space from the house attic space? IRC R803.2.1.2 is the only thing that I can think of that would be an exception to R317.

Can somebody set me straight for this type of installation. First time this has been done that I know of.

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Originally Posted by Kevin Luce

I did an inspection on this 4 year old duplex where fire rated drywall was installed in the attic separating the two units. I went into the garage attic and the same drywall was installed in the same way (all the way to the roof). Then where the over the attic space stopped and the space where to roof sheathing began (separation of the garage space and house attic space) there was no drywall separating the two units. I can literally go up into the attic from the garage at one unit and walk around the firewall and enter the next unit's garage attic space. Is this installation correct and if so, is it because of the wood sheathing is separating the garage attic space from the house attic space? IRC R803.2.1.2 is the only thing that I can think of that would be an exception to R317.

Can somebody set me straight for this type of installation. First time this has been done that I know of.

I would have to say that is not a correct firewall.
Look at the code a little further down. I'm assuming this was from the 2003 IRC.

R317.2.1 Continuity. The common wall for townhouses
shall be continuous from the foundation to the underside of
the roof sheathing, deck or slab and shall extend the full
length of the common wall including walls extending
through and separating attached accessory structures.

Scott is correct. It is not only incorrect but incomplete and not effective.

Aaron