[donlino]

Hello all, I have finally decided to move forward and build a dedicated home theater room in my basement. Here is some general info:

Width: 13 '
Length: approx 24' 8"
Ceiling is 8'4" in main area and 7'4" in entrance area
Entrance will be to the rear on the right
leather couch 1st row
2nd row will have 5 Berkline powered recliners (45004s) with mini-Buttkickers and lighted cupholders
8"? riser for recliners
106" Grey Wolf II Screen (1.8 gain)
Optoma HD70 Projector
Infinity Beta 50s Front L & R
Infinity Beta C360 Center
Haven't decided on 5.1 or 7.1
Velodyne CT120 sub and Klipsch 8" sub
Also haven't purchased surrounds yet but may purchase Infinity Classia C255ES to help match to existing speakers.
I am thinking about installing a subfloor on top of the concrete flor and may use Dricore (does anyone think this will help isolate the sound?)
Ceiling is already drywalled but plan on adding 2nd sheet of 5/8" with Green Glue. I think I will also blow in insulation above the 1st layer of drywall on the ceiling.
Left wall and rear wall will be double wall construction with 2 sheets of 5/8" on each with Green Glue in between the sheets. 1" air gap between the walls. R13? unfaced insulation in each wall.
Should I also use mass loaded vynil?
I plan on using acoustic caulk on the first layer of drywall since I don't think I need to tape and mud the first layer. Will also use the caulk at top and bottom of walls. Does first layer go on horizontally and 2nd vertically?
Front wall and right wall are already drywalled. There is concrete foundation wall behind these two walls. Assume not necessary to add 2nd layer to these?
I am thinking of using the plastic insulating stuff that builders use for sill plates under and above the 2'x4' plates to help isolate the top and bottom of the left and rear wall.
Would like to install 4" airtight can lights along the sides of the walls but concerned about sound escaping.
The area currently has 2 HVAC supplies but no returns. I am very concerned about sound travelling throughout the house via the ducts so may rip open existing ceiling drywall to either use flex duct or install some type of silencer??
Thinking of having cabinets built for front which will also frame around my pull down screen. Equipment would go in top left cabinet covered by door, all speakers would go in cabinet and would of course have speaker cloth in front of them. I believe I should put sand in the base of the cabinets to help with the acoustics. Also would put insulation in the riser for the recliners. I have 2 subs one Velodyne front firing and 1 Klipsch down firing (assume it would be ok to also put these next to the left and right speakers in the front cabinet?)
I am also thinking of putting in a counter behind the recliners with some bar stools but not sure.
There are 2 electrical panels in the front right wall which I will have to work around (currently covered by the white cabinet you see in the pic). You will also see that there is a bar/kitchen area behind the home theater area that I also plan on remodeling to help make the basment more of a man cave.

I don't know how to use any of the design software so I am attaching my sketch made in Excel. Also attaching pics of the before. I had built a temporary riser which you will see in the pics. I welcome your thoughts and suggestions to help me build out my home theater so I can crank the movies without having my wife yell anymore! Thank you.

 

[Ted White]

Wow. Plenty of questions. If you have concerns about sound leaking into the rest of the house, then you'll need to consider all surfaces. Floor won't acoustically benefit from the Dricore, though it may be cozier.

 

[bpape]

Agreed. It'll be warmer and give you a little more feel. It will help a tiny bit in reducing flanking through the slab but not a lot. If you were to build walls on top of the Dri Cor, that can help.

The cans are defnitely an issue unless you build back-boxes behind them all. You'll need to do the same for switches, outlets, etc. Also, don't forget HVAC.

Bryan

 

[Ted White]

I would only ever recommend that the wall is framed to the slab, sealed with a sealant to the slab and then drywalled before any floor treatments, stages risers, etc are built.

 

[bpape]

Difference of opinion. I do walls on top of subfloors like that all the time for a little extra decoupling. Yes - we still use sill gasket under the walls and seal the walls to the floor.

Doing the walls direct to the floor, sealing, and floating a floor in the middle will work too.

Bryan

 

[Ted White]

The way to view it is that a larger gap / opening will require more mass. Small cracks can be handled with sealant, but Dricore is 7/8" and that's just huge.

So the best gap is no gap. Foams under walls have no mass and aren't sealants.

The wall won't vibrate that floor, and the floor won't vibrate that wall, so decoupling really offers no demonstrable benefit.

The Dricore is relatively low mass so safe to say that it won't shield the floor from anything. It does have little dimples underneath and that air cavity created is not a great thing. Not sure what the resonance point might be, but likely too high to approach the coincidence point of that slab.

 

[bpape]

Agreed the foam isn't massive. It's purely an air thing. That's why we still caulk on both sides of the base plate of the wall.

I'd agree that the resonance is way above the conincidence point.

As for it helping, I just look at it from a practical standpoint. I've heard what it does and IMO it does provide a small benefit for basically no more money over floating the wall inside.

I understand your point about the 7/8" 'gap' underneath.

Bryan

 

[Ted White]

Curious is the wall is resting on the 7/8" Dricore, how do you seal the backside of the bottom plate where the 7/8" gap is?

 

[bpape]

The rear of the bottom plate is just inside the edge of the Dricore. It's caulked just like the front side is. No 7/8" gap between wall and Dri Cor.

Bryan

 

[Ted White]

Ah, OK. So just the "open" edge of the Dricore is exposed on the other side?

 

[bpape]

Yes - that's correct. If we can, we run it to within 1/4" (depending on temp changes in the area) of the foundation or outer wall where possible and caulk that edge too.

Bryan

 

[donlino]

This is helpful. I was only planning on installing the Dricore subfloor becasue I thought it would be helfpul in decoupling the room and would help keep the bass in the room. I don't have any issues with a cold floor so sounds like I can omit the plan for the subfloor. Is there any decoupling benefit in installing a subfloor in a home theater room that is built in basement with a concrete slab or this only appropriate on 1st or 2nd floors that are built on wood? Or would I need to build a traditional floated subfloor with 2x2s, insulation, plywod etc. to achieve any real decoupling for my room since it's over concrete? Also, is there any benfit in using a sill gasket above the top plate of the walls to help decouple them from the ceiling since my ceiling is already drywalled? (I do plan on adding a second 5/8" sheet to the ceiling with Green Glue but same issue applies the top plate of the wall will still be in contact with 2nd new sheet). Thanks!

 

[Ted White]

Is there any decoupling benefit in installing a subfloor in a home theater room that is built in basement with a concrete slab

No

or this only appropriate on 1st or 2nd floors that are built on wood?

Yes, or a poured gypsum floor above grade

Or would I need to build a traditional floated subfloor with
2x2s, insulation, plywod etc. to achieve any real decoupling for my room since it's over concrete?

Not necessary

 

[donlino]

Got it makes sense. Will I have a weak link in my decoupling if I don't do anything to treat the right and front walls of the room that are already drywalled? The concrete foundation sits behind them. The option as I see it is to add a second sheet of drywall (5/8") to the front and right walls with Green Glue in between. My guess is the builder used 1/2" on the existing front and right walls even though I would be building the new left and back double walls each with 2 layers of 5/8", hopefully that won't screw up the acoustics. As for my ceiling is the best approach to blow in insulation above the existing 5/8" drywall and then Green Glue followed by new 5/8" drywall sheet? Is there a better approach such as putting the new sheets on furring strips below the existing ceiling (although that would decrease headroom)? Would appreciate your thoughts.

 

[Ted White]

Would you know if the wall framing is spaced from the concrete? Or is the framing pushed right up to the foundation?

R19 Batt insulation in joists is great. R13 in walls.

You would not use clips, furring or spacers on any kind on existing drywall. The small air cavity will cause big problems.

 

[donlino]

I will check later today. I think there is a smaill space between the studs and the foundation wall but probably not much. I don't think I can use batts in the ceiling since it's already drywalled with one sheet so I believe my only option is to poke holes and blow-in insulation. Should I try to completely fill the cavity or leave an air gap?

 

[Ted White]

A small space between the studs and foundation is all you need to have those walls officially decoupled. So you can just add drywall to the existing walls.

Go for a light density application of cellulose. This stuff is often over-packed and then starts conducting vibration. There's no advantage per say to leave an air cavity other than it ensures no over-compaction.

 

[donlino]

Ted, you indicated that I should just add drywall to tthe existing walls (front & right walls) but I thought a second sheet on those walls is not necessary since they are in front of the concrete foundation walls. Can you please clarify?

 

[Ted White]

We're not concerned about sound exiting through the concrete into the dirt. We are, however, concerned about sound passing through single drywall and headed straight up into your floor joists. Common flanking path.

 

[donlino]

Has anyone installed backer boxes for can lights in a ceiling that's already drywalled? Just curious if the degree of difficulty increases substantially as a result of the existing drywall. Also, is the best approach to use acoustic caulk on the first layer of drywall for my double wall construction or should I just tape and mud the first wall? Thanks.