I’m looking at how to mount a ledger on a short firewall that sits on top of a parapet. I believe it’s one or two-hour fire rated, and I don’t want to change that.
The wall is 43″ high, 2×4 studs covered with 5/8″(?) drywall on both sides, and then exterior plywood. The lower 5″ of plate/studs is exposed with EPDM roofing lapped up onto it, and 2×4 blocking inserted behind to support the membrane.
It wouldn’t be hard to saw off the bottom 7″ of the sheathing to mount the ledger directly on the studs (with membrane, flashing, etc.) but I can’t find any info on whether this is fire-rated. Since the bottom of the wall is blocked with 1.5″ fir I assume that 2x wood is an acceptable fire barrier, but I can’t find any info to support that conclusion. Mounting directly would also help stabilize the wall since it isn’t top-supported.
The other option is to space it out and leave all the sheathing as-is. I know that’s a recommended method to leave an airspace, but all the info I’m finding now is saying that there’s little structural credibility in going through spacers and siding.
Either way would probably be OK, but I’m curious to know what people think.
Replies
Just make the deck freestanding and you dont have to worry about it. That is how the local codes require it now in this area.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
It can't freestand; it's spanning a roof with dodgy framing. I decided to put joists from one parapet to the other, but one side has the firewall.
Edited 12/6/2008 10:25 pm ET by KHWillets