Author Topic: Basement Walls/Ceilings  (Read 2921 times)


  • Guest
Basement Walls/Ceilings
« on: January 26, 2002, 02:51:38 AM »
I'm drawing up plans and preparing the list of materials I need for a basement soundproofing project, and I have a few questions. I've ordered the EPA book and read through it and your site carefully, and I think I have a good understanding of mass, decoupling, and blocking transmission path, but a few questions are nagging me, and I want to resolve them before I begin.
I have a large unfinished basement with concrete walls and floor.  I'm making a soundproofed room in one part of it for playing drums and in a band.  I plan on making double walls with two sets of metal studs, with various combinations of absorbent mat, soundboard and drywall on the inside face of the inside studs and outside face of the outside studs.  I plan to use RC on the exposed ceiling joists or to build a complete second ceiling, with a combination of mat, soundstop, and drywall.
The walls will not be attached to any existing walls, only resting on neoprene on the floor and attached at the top to either the exposed joists or the ceiling drywall. The rest of the basement will remain unfinished, but used for laundry, workshop, etc.
I haven't seen a satisfactory answer to this on your site or elsewhere.  How do I fit the walls together in the corners?  If I butt wall one up to wall two (like a 1/4" away), and then caulk the joint, the end of wall one is covered, but the end of wall two is open, and so the second set of studs for wall two won't have any effect.  The sound will just escape out of the end between the sets of studs.  If I bridge that gap with something, like mat and drywall, it seems like I'm shorting out the two sets of studs, defeating the purpose of having two sets of studs in the first place.  
Should I interlock the two sets of studs somehow -- i.e run outer and inner sets of studs of wall one up to the outer set of studs of wall two, then run the inner set of studs of wall two up to the inner set of studs of wall one?  Or is it better just to close up the ends with mat and drywall and live with the decreased isolation?
The same question applies where the ceiling meets the walls.  If I run both sets of studs up to the RC/drywall ceiling (with a 1/4" space caulked), the sound will pass through the first layer of ceiling drywall and out through area between the joists and over the walls into the rest of the room and house. If I run the studs up to the joists and run the ceiling over to the walls, I have the same problem as above -- the second set of studs have no effect.
Second question:  The ceiling has exposed 8" deep joists.  It seems that if I'm using RC, it would be better to attach the RC directly to the joist and apply my mat/soundstop/drywall combo to that, as opposed to adding a number of layers of mat/soundstop/drywall directly to the joists, and then adding the RC and then more mat/soundstop/drywall.  The wisdom appears to be that the extra dead air space is better than dividing it up, and so the layer of materials attached directly to the joists are a waste of money and effort.  Is this correct?
Many thanks for any help you can give me.  I love the site.