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Discussion Starter · #1 ·
OK, I am ready to start my basement home theater. I have a good amount of space but I do have some challenges. I am attaching a simple pic of what the layout looks like and what I want to do.


What I have:


The basement space I want to construct is roughly 26x17 and I need to install a door at the end of the home theater for access to a 4 x 17 room where the electrical panel and sump pit are. I was also hoping to build a bathroom at the other end of the room using a flush up pump. I am debating whether to put in a pocket door for access to the bathroom. I have a rigid AC duct running down the back side of the room that has three brances also using rigid ductwork off of it to feed air into my first floor. The floor of the basement is a concrete slab, the basement walls are preinsulated precast wall system (SuperiorWall System w/R12.5 foam insulation) and the joists are engineered I joists.


What I have done so far:


I started to put down 2x6 PT wood for a bottom wall plate 6 inches from the existing wall. I have them anchored into the slab using regular bolt anchors and under the plate I put down two layers of mass loaded vinyl. I started to build a soffit attaching it directly into the bottom of the I joists with two layers of MLV in between. I also began to attach a top wall plate into the I joists with again two layers of MLV in between and begin building some of the walls using a staggered wall construction. Everything I was building was screwed together using 2-1/2" decking screw. I intended to screw sheetrock into the back side of the wall using regular sheetrock screws and such. I also planned to screw sheetrock into the inside of the soffits. On the inside part of the wall I was going stuff in R13 and then use Whisper Clips and Hat Channel then two layers of drywall with green glue in between.


Next Steps and Recommendations:


I am not sure if I should have attached the soffits and top wall plates into the I joists. I am now doubting whether even using the MLV was worth it based on some of recent research. I am willing to tear it all down and redo it another way if it makes sense. What I am hoping to find is whether I should attach the walls another way to I joists? Should I attach the whisper clips directly to the I joists for the ceiling? Should I replace my rigid main AC feed with flex duct? I was thinking of adding two layers of sheetrock with green glue in between and on the first layer in between the I joists and beneath the first floor subfloor too then insulation. Is it worth it?
 

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Without seeing the full basement plan, I have two observations:

1. The door to access the sump pit could be moved to the sump pit end, so then you can use the space for equipment closet.

2. You have to open two doors on both short end of the room, one is the screen wall, so if it is possible, consider move the entrance door to the side of mechanical room/workshop area, then you can have the wall next to the stair as screen wall and wall back to the sump pit as back wall, with equipment closet behind it.
 

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mykola:


MLV under the framing isn't a good idea. Potential flanking path for one thing, and it does nothing to aid isolation for another.


MLV in wall and ceiling framing risks trapping small amounts of air, yielding a Triple Leaf: http://www.soundproofingcompany.com/...e_leaf_effect/


The pocket door won't stop sound, so the entire bathroom would need to be treated as you plan to treat the theater room.


You say there's a 2x6 wall going in front of the old wall. Does the old wall have the old drywall removed to expose the old wall studs?


This might help: http://www.soundproofingcompany.com/...within_a_room/
 

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Discussion Starter · #4 ·
OK, I can definitely remove the MLV (Auralex Sheetblok). That's easy enough and the old wall is actually the foundation which has metal studs built into the concrete. It's this wall system:

http://www.superiorwalls.com/products_xi.php


Should I place anything under the 2x6 walls for dampening? The room within a room is almost the direction I am going in but how would I attach the top wall plate to the I joists? Currently, I have them screwed into the I Joists but I was wondering if I should get some type of clip instead? I wanted to put sheetrock on the outside of the staggered 2x6 wall and then clips with two layers of drywall and green glue in between on the inside. Does this still make sense? The last thing I thought about was layering 1" foam down on the floor with a 1/2" gap sprayed in with foam around the edge of the room then 2 layers of 5/8-3/4" ply with green glue in between those layers. Is this the wrong way for the floor too?
 

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Quote:
Originally Posted by mykola /forum/post/18274831


I started to put down 2x6 PT wood for a bottom wall plate 6 inches from the existing wall.

Sounds like a waste of 5 inches.


Lets see some pictures of the as is build.
 

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Discussion Starter · #6 ·
OK, here we go. I attached a few pictures of what's in place now. I included a pic of the base plate with Auralex underneath the PT plate and then pics of the walls.




 

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I think I would have used clips and channel on the walls directly applied to those high tech walls with pre-built studs. That would save you about 6 inches on exterior walls. You also don't need staggered studs on exterior foundation walls. PM Ted White and ask him to take a look. I've never seen a theater built in a basement with those walls but I assume they are designed to have the drywall directly mounted to the protrusions.


I'm not certain that building up the floor is the method I would have picked for the bathroom. I would have dug a sewage ejection pit and chiseled paths to the pit for under concrete drains. By keeping everything one level you increase the value of the finished space. The one exception I can think of is if the entrance to the bathroom will be off the elevated seating riser.
 

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Here are a couple of thoughts.


The door (I assume there will be a door) to the bathroom will allow quite a bit of sound into the stairwell framing. We try hard to avoid stairwells.


The door to the sump pump area similarly will allow sound vibration to enter the ceiling joists behind that wall.


Doors are always a weak point and we're better off with only one entrance if possible. You have three.


The MLV in this instance isn't helping and could hurt. I say this for the larger readership. I would leave well enough alone with yours. Just seal it well.


You would generally only deplot a staggered stud wall when dividing up the living space in a basement. Divide the area in two with a staggered stud (preferably a double stud) wall system. Next to the massive foundations we only need a single stud wall.
 

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Discussion Starter · #10 ·

Quote:
Originally Posted by BIGmouthinDC /forum/post/18282921


I think I would have used clips and channel on the walls directly applied to those high tech walls with pre-built studs. That would save you about 6 inches on exterior walls. You also don't need staggered studs on exterior foundation walls. PM Ted White and ask him to take a look. I've never seen a theater built in a basement with those walls but I assume they are designed to have the drywall directly mounted to the protrusions.

The walls are definitely made to have sheetrock directly attached so that is definitely an option for this wall system. I'll probably do that in the other half of the basement for the bar but the room itself is still pretty big so we thought what's a lost 6" or 12". :) We also thought another wall would give us a little more isolation though now the staggered wall is sound more and more like overkill!


Quote:
Originally Posted by BIGmouthinDC /forum/post/18282921


I'm not certain that building up the floor is the method I would have picked for the bathroom. I would have dug a sewage ejection pit and chiseled paths to the pit for under concrete drains. By keeping everything one level you increase the value of the finished space. The one exception I can think of is if the entrance to the bathroom will be off the elevated seating riser.

There was a lot of hesitation on my part for the bathroom in building up the floor. The biggest being we were not comfortable chiseling out the concrete that close to the stairs and lolly columns. We know the ejection pump works great (we use one in my parents house) but the sound leakage is definitely an issue. I am hoping to isolate it by building it its own little isolation box and then having it actually on the other side of the wall in the mechanicals room.
 

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Discussion Starter · #11 ·

Quote:
Originally Posted by Ted White /forum/post/18283869


Here are a couple of thoughts.

The door (I assume there will be a door) to the bathroom will allow quite a bit of sound into the stairwell framing. We try hard to avoid stairwells.

I am certainly not stuck with the design as it is now so based on your comments would it make more sense to add a door to the outside next to the stairs and before the door into the HT area? That's easy enough to do.

Quote:
Originally Posted by Ted White /forum/post/18283869


The door to the sump pump area similarly will allow sound vibration to enter the ceiling joists behind that wall.

I am kind of stuck with that area as there's no real way for us to isolate it or give it another entrance but I had a thought. I saw on the green glue site that they recommend adding a layer of sheetrock with green glue underneath the first floor subfloor, sealing the edges with accoustical caulk and then more green glue and another layer of edge sealed sheetrock. I was thinking of doing that anyway so would that help there? I can also finish off the walls with clips, rock and GG. Is the whole insulating the subfloor a waste of time? Here's a pic of this.



Quote:
Originally Posted by Ted White /forum/post/18283869


The MLV in this instance isn't helping and could hurt. I say this for the larger readership. I would leave well enough alone with yours. Just seal it well.

I guess it's a learning process. The one wall closest to the doors I may just take down anyway and redo with a single wall. Should I butt it closer to the foundation or does it matter? Should I also look at using something else to attach it to the I joists or just screw it into the bottom of the joists like the old wall?
 

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I'm pretty familiar with that image...



I don't think that's necessary. If the sump doesn't operate often, then it may not be an offending noise source, If that's the case then you could simply extend your acoustic envelope to include the sump room. Then no worries about the door, and you would simply build that sump room wall after the main room has been framed and drywalled. Just as we would frame a screen wall.
 
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