Thread: Duplex 1hr Separation Wall (Yes or No)

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Originally Posted by Sean Dooley

Tell me if this sounds right for a 1hr separation wall in a duplex. I know that the 4ft rafter flare is not required in a duplex and that you can get by with a draft-stop in the attic if you use 5/8" Type-X on the interior ceiling, but wanted to run this by anyways.

Duplex Party Wall (1hr Required)

Wall was built with two layers of 5/8" Type-X square edge with joints staggered minimum of 16" vertical and horizontal. Joints are not taped. The 2x4 wall framing in the attic is only on one side of the duplex so both layers of 5/8" Type-X are nailed to 2x4 wall framing on one side of duplex.

Essentially they were trying to place two layers of 5/8" Type-X in the middle of two 2x4 stud walls, but they nailed both layers to only one of the 2x4 walls. Both of the middle 2x4 walls are load bearing. From removing the plug plates it looks like the interior side of the separation wall has 5/8" Type-X as well. I have seen this done before with another builder but I wanted to get your opinions.

You have not described a prescribed "1-hour" wall nor a prior or present (tested) UL assembly rated as same. You did not reference age nor the applicable cycle for construction. I won't defend your presumptions above, nor bother to decode some of your statements ("plug plates", etc.).

I won't go into elaborate detail, but taping & mudding at seams and mudding fasteners both layers both sides of stud separation wall is always a part of a one-hour assembly, exposed framing of the structural wall is never a part of same, stopping and blocking is always a part of same.

You made no mention of the roof structure, etc. Nor reference to your access to the attic area (perm. access ladder or scuttle) its protection/separation from living space, nor presence of mechanicals, etc.

Insulated separation wall as exterior wall quite impossible as you described as well.

2-family homes are not necessarily duplexes.