Author Topic: Floor - a 6 layer plan. Redundant? Effective?  (Read 6445 times)


  • Guest
Floor - a 6 layer plan. Redundant? Effective?
« on: October 05, 2010, 01:38:48 PM »
I own a home with 3 rental units.  I live in the the top floor currently, and I want to reduce as much as possible the sound transmission from my unit to downstairs.  The following is my plan.  Please tell me if I'm wasting my time on any portion of this plan. 

1.  resiliant channel and an extra layer of drywall on ceiling of unit below, (done already)
2.  rip up upstairs floor and subfloor
3.  bats of sound insulation, (roxul safe and sound), between the floor joists
4.  1 1/2" styrofoam as a top layer between floor joists
5.  accoustical caulk the perimeter of the styrofoam to seal all air leaks
6.  layer of MLV, (mass loaded vinyl), over top of joists
7.  two layers of 5/8" subfloor, (total of 1 1/4" of subfloor plywood - tongue and groove)
8.  3/4" prefinished Maple hardwood flooring

I'm not getting my hopes up too much about the impact sound, but I do want to reduce the airborne sound like voice and music from traveling from my upper unit down to the tenant below.  The biggest concern area is my dining room/kitchen, which is directly above the two bedrooms of the lower unit.  I can reiterate the above plan to the following concepts:

1.  Resilliant Channel and drywall  -  attempt to help the impact sound, (at least the extra drywall must help somehow)
3.  Roxul sound bats  -  one layer of sound wave absorbing material
4.  Styrofoam  -  another layer of a different density to confuse and reduce the sound wave
5.  Apparently if you have a 3% surface breach in air seal, it can cause up to a 50% decrease in soundproofing effectiveness
6.  Mass won't help impact but it does help air born apparently
7.  Again extra mass helps, plus I can afford the higher floor level as it will be transitioning to a higher tile surface
8.  This is just my choice of flooring for home value, but I hope it acts as a further mass to block air born with its mass

This above plan is my best effort from my research, but I fear that some of the layers are relatively ineffective and unnecessary. 

  Can anyone verify this?  I would rather save the money on some of this stuff if its not going to help much.




  • Guest
Re: Floor - a 6 layer plan. Redundant? Effective?
« Reply #1 on: October 05, 2010, 02:28:25 PM »
Skip the Styrofoam, but be sure to seal the seams in each layer of subfloor before installing the finish floor.


  • Guest
Re: Floor - a 6 layer plan. Redundant? Effective?
« Reply #2 on: October 05, 2010, 02:49:37 PM »

  If sealing is so key, should I hose down all seams along the bottom of the joists and the original ceiling drywall downstairs?  Maybe along the drywall seams themselves as well?  I assume if sealing is so key, it would be best to start the air tight sealing as low down in the layers of this floor as possible.  Does that make sense?



  • Guest
Re: Floor - a 6 layer plan. Redundant? Effective?
« Reply #3 on: October 06, 2010, 02:54:59 PM »
Act as if you'll be filling the joist cavities & room above with water - anywhere it can leak through, you should seal.  It only takes a tiny gap or crack to destroy your soundproofing. 

Is the first layer of drywall below attached directly to the floor joists?


  • Guest
Re: Floor - a 6 layer plan. Redundant? Effective?
« Reply #4 on: October 06, 2010, 05:18:53 PM »
  I put up resilient channel and 5/8" drywall over the original drywall downstairs.  I'm pretty sure its drywall on the original joists, as opposed to over plaster and lathe, if that's what you mean.  It seemed to do nothing for sound, (my girlfriend seems to think its worse). 

  But if sound air leak is key I can focus on that.  I mean the ceiling was mudded and taped and there is no actual air coming through except for on the ceiling light probably, but I will make sure that's sealed well.   That's the easy part.  I have boxes of acoustical caulk left over from a previous job i did, (I never realized how important that stuff was when I was using it).   So its not just sealing air movement from from one floor to another, but its sealing every layer of material to best experience the maximized effect that material's mass can offer right?  I think I get it. 

  So seal the original ceiling where ever possible,
  Seal the MLV layers, seams, perimeter
  Seal full perimeter's of each tongue and groove plywood sheet on both layers and perimeter,
  And sealing each piece of wood flooring is probably overkill . 

  I think that's really the best I can do in this situation. 



  • Guest
Re: Floor - a 6 layer plan. Redundant? Effective?
« Reply #5 on: October 07, 2010, 03:47:54 PM »
Well, it would have been better if you'd torn the original layer of drywall off the ceiling and put 2 layers on resilient channel to make the ceiling 'springy', but what's done is done..

Once you start sealing, I think you'll clearly see the difference in noise reduction.  And you're right, sealing each piece of finish floor isn't worth the effort. 

Also, if you have recessed lights in the ceiling below, you want to make sure you have the 'airtight' boxes, the ones rated for direct insulation contact.  The unrated ones are way too 'leaky' and are too difficult to seal.  It might also be a good idea to build a box around the can, or at least glue drywall on the sides and top to get some mass to compensate.  Seal/tape the seams, too

If you have a regular ceiling electrical box, you could also make some kind of enclosure to cover it, but you could probably just goop it up with caulking (~1/2" thick or so) and you'd be okay.