avoiding the triple leaf effect with a brick party wall

arnold4321

Standard Member
I live in an old rowhouse and the party wall is two layers of brick. I'm wondering what kind of interior wall to construct to reduce sound coming from the neighbors, and also lessen any noise I send their way.

In the party wall, there is a slight gap between layers in most of the brick courses. This photo shows the gap between layers -- you can see it back behind the bottom of the outlet where the bricks are missing:

6560086317_1df351b5f6.jpg


Every 15 courses or so, the bricks are turned lengthwise so that they span the width of the wall. See the course in the middle of this photo where the mortar joints are closer together:

6560079585_5522deea55.jpg


So, is this brick wall two leaves or one? And if my neighbor has a 2x4 frame wall on the other side, what should I build on my side for noise reduction purposes?

I'm willing to give up the four+ inches of space needed to create an insulated stud wall set apart from the brick wall, but only if that makes sense from a noise reduction standpoint. Otherwise I would affix foam insulation (for thermal purposes) to the brick and attach drywall directly to the foam. That would be a way to provide thermal insulation and *avoid* adding a new leaf. Though of course there would be tiny gaps between the brick and foam since the brick wall is not perfectly flat.

What to do? Let me say that, if you are good enough to reply, there's no need to bring up the flanking issue. I'm aware of that consideration. In this post I'm just asking about the wall system on the party wall. Let me say also that I plan to replace those missing bricks and repoint in the few places where it's needed using a lime mortar.

Many thanks.
 

Peter Parker

Distinguished Member
You might want to ask one of our members - Ted White - he knows his stuff with regards to issues like yours, and has a handy website that might be of some help too:

Significance of Air Cavity Depth & Triple Leaf Effect - Soundproofing

A stud wall built an inch away as you describe would usually do the trick, but when as close to a double brick wall as yours, it becomes more complicated as you say, so hopefully Teds experience there may help.

Gary
 

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