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post #1 of 14 Old 10-15-2018, 11:39 AM - Thread Starter
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So in addition to building out a dedicated theater room, we're building out our entire basement and having a general contractor do all the work.

As budgeting did not allow me to hire a separate theater specialist, it's been up to me to do all of the research for the theater build and relay what needs to be done to the contractor, who has never done a truly dedicated theater room.

He came to me today and said that the clips and hat channel wouldn't be needed because he thought of a cheaper option of just using a foam backer board behind the drywall. I tried to explain that this really wouldn't uncouple the structure as needed but he insisted it would because the drywall is not touching the studs/joists.

So if he's correct (I really don't think he is) this would obviously be a cheaper option. If not, can someone please help me with some kind of technical jargon on why he's wrong and it needs to be done the normally accepted way?

Thanks again for tolerating so many new questions.
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post #2 of 14 Old 10-15-2018, 11:46 AM
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Quote:
Originally Posted by matpal View Post
So in addition to building out a dedicated theater room, we're building out our entire basement and having a general contractor do all the work.

As budgeting did not allow me to hire a separate theater specialist, it's been up to me to do all of the research for the theater build and relay what needs to be done to the contractor, who has never done a truly dedicated theater room.

He came to me today and said that the clips and hat channel wouldn't be needed because he thought of a cheaper option of just using a foam backer board behind the drywall. I tried to explain that this really wouldn't uncouple the structure as needed but he insisted it would because the drywall is not touching the studs/joists.

So if he's correct (I really don't think he is) this would obviously be a cheaper option. If not, can someone please help me with some kind of technical jargon on why he's wrong and it needs to be done the normally accepted way?

Thanks again for tolerating so many new questions.
Sometimes it's easier to cut to the chase.

The technical jargon is that it's the way you want it done, he's the contractor and your paying the bill.
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post #3 of 14 Old 10-15-2018, 12:05 PM
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your contractor is full of crap. Containing low frequencies requires mass dampening and isolation his proposed design doesn't have it. Here is my talking point when I meet with contractors






Contractor construction notes
High Performance Home Theaters

Building a Drywall sound isolation shell

Four principles of sound Isolation are utilized:

MASS - ISOLATION-ABSORPTION-DAMPENING

  • Loose fill insulation in walls and ceiling
  • two layers of 5/8 heavy drywall
  • Green Glue dampening compound between layers
  • Drywall installed on a clip and hat channel isolation system with 1 1/4 and 2 inch long screws for first and second layers respectively
  • Clips and channel spaced per vendor specifications, no more and no less. Clips staggered on all available studs and joists, additional studs will be required in all inside corners for adjacent clip clearance.
  • Channel is 25 ga 7/8 inch tall furring channel (Hat channel) do not use 22 ga
  • Install drywall in sequence that results in a cascading joints and overlapping seams. First layer ceiling, then first layer walls, second layer ceiling, second layer walls.
  • Every hole cut in the drywall shell needs to addressed with a backer box, a putty pad, acoustical caulk or by other means. This includes items such as outlets, switches recessed light fixtures, in-wall speakers. Where possible these items will be installed inside the theater shell by passing wires through small holes which caulking around the holes.
  • Items such as seating risers, stages, soffits will be built after the drywall shell is constructed unless they are required to hide piping or ducts. In those cases the covering of the soffit will be the same construction as the sound isolation walls and ceiling.
  • If walls are non load bearing frame the walls one inch short to the ceiling joists and securing the top plate with IB3 clips spaced at the end of the walls and every 48 inches. Add additional clips above the hinge side of door framing. This will improve vibration isolation
  • Consider double wall framing or staggered studs for critical walls where sound isolation is critical, bedrooms, stairways etc.

Electrical- Theater Room

Low Voltage

  • Minimum of 1 1/2 inch diameter electrical conduit to projector location from equipment stack location - for future cable swaps as HDMI standards change.
  • No wall penetrations for speaker wire wall plates just caulked holes.
  • Consider wiring for convenience connections, Cat6 for network, game connections at front of riser. Run in conduit and down to riser inside speaker column. Inside riser run to the front face.
  • Thermostat wiring through hole in wall, caulked
  • Wiring for temperature sensor inside hush box (if any) to utility room and future exhaust fan, based on selected fan.

Line Voltage

  • Projector outlet connected to power inlet in equipment stack location , not breaker box
  • Recommend all other outlets mounted inside theater shell. Outlets at sides of columns furthest from the door, surface mounted behind screen, front face of riser in center, top of riser for back of second row of seating. If holes are cut for electrical boxes they must be dressed with putty pads. Leave extra service loops at each location with wires hanging inside of room passing through small caulked holes.
  • Zone lighting circuits in room, recessed lights over screen, sconces, ceiling recessed fixtures front of room separate from rear of room, step lights for safety All lights on dimmers. Consider connected controller with simple key pad in room. Any holes cut other than soffit and riser lights need to be in backer boxes or covered with putty pads.
  • Several dedicated 20 amp circuits (4-5) at equipment stack location. Install whole house surge protection.

HVAC

Overall goals: sufficient quantity of air to maintain 72 degrees routinely, the room will be an air tight sealed room with a seating capacity of _____ adults and maybe kids sitting on the floor. The air flow should be sufficient and quiet. Noise criterion goal of NC20

· room connected with oversized ducts to maintain quiet slow flow
· velocity at face of ducts 250 ft/min or less
· bar diffuser vents on bottom of soffit/ceiling. two supplies in front, two returns in bottom of rear soffit. (Dayus from HVACquick.com) probably 4x48 inches
· Use soffit as a sound break with partitioned chase-way zones, air coming in from ceiling and traveling horizontally inside soffit before exiting. Line chase-ways with JM Linacoustic.
· Connect theater with either insulated flex duct or Linacoustic lined metal ductwork.
· Separate zone with thermostat control with thermostat inside theater.
· 4 inch duct run from ceiling inside hush box (if included in design) location to utility room.

Stage

· Build after the room is drywalled
· Build with at least 1/2 gap to wall
· decking is three layers of 5/8 OSB with Green Glue between layers
· Line each cavity with plastic and fill with play sand.

Seating Riser
· interior is one large connected air space filled with insulation
· Vents will be cut on top surface at back per final plans so that the riser functions as a pressure relief bass trap.
· add step lights and outlets
· decking is three layers of 5/8 OSB with Green Glue
Door
  • 1 3/4 inch thick solid core with Zero International perimeter door seals automatic door bottom. Install hard surface door threshold to mate with door bottom, order/make custom width jamb
  • Best practice is communicating doors, one swinging in one swinging out creating an airlock.

Floor (Best practice)
  • 1/2 inch rubber mat (Serenity Mat) secured to floor with DA5 adhesive 3/16 v notch trowel
  • 3/4 T&G OSB glued with DA5 to mat. OSB floated with no mechanical fasteners.
  • Stage and Riser built on top of sub-floor.
  • Locally sourced Horse Stall mats can be substituted if available cheaper (Tractor Supply)

Last edited by BIGmouthinDC; 10-15-2018 at 12:19 PM.
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post #4 of 14 Old 10-15-2018, 01:05 PM
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The telling statement is "the contractor, who has never done a truly dedicated theater room". He may have what he things are great ideas, but they cannot compete with tried and proven methods that are recommended by professionals who HAVE built dedicated theater rooms and other similar environments. Do you want it done right, or do you want it done cheaply? If you want it done right, follow the advice of those who have done it successfully. If you want it done cheaply, follow the advice of your contractor, but don't expect a room that is much different than every other room in your house.

Jeff has laid out a detailed and well thought out plan. If followed successfully, it has all of the basics to build a theater room that functions well and that you can be happy with. As b curry says, it is your house and your money.
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post #5 of 14 Old 10-15-2018, 01:09 PM - Thread Starter
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That is amazing, thank you so much.

Just curious why the risers would be built after the drywall.

And just be clear, the foam backing offers no decoupling at all?
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post #6 of 14 Old 10-15-2018, 01:14 PM
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If the drywall is screwed to the studs through the foam it defeats any decoupling the foam provides.


framing the risers or stage before the drywall goes up creates a series of gaps and if the riser isn't built to the same standard as the walls will leak sound. I'm assuming it is already framed and your screwed right? Also framing before eliminates the opportunity to use it for low frequency management using the riser as an absorber of resonant frequencies.
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post #7 of 14 Old 10-15-2018, 03:21 PM - Thread Starter
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Quote:
Originally Posted by BIGmouthinDC View Post
If the drywall is screwed to the studs through the foam it defeats any decoupling the foam provides.


framing the risers or stage before the drywall goes up creates a series of gaps and if the riser isn't built to the same standard as the walls will leak sound. I'm assuming it is already framed and your screwed right? Also framing before eliminates the opportunity to use it for low frequency management using the riser as an absorber of resonant frequencies.
The riser is not yet framed, no.

Is it secured to the wall(s) in any fashion? IB3 clips?
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post #8 of 14 Old 10-15-2018, 03:35 PM
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IB3 clips decouple the top plate of framing for walls inside foundation walls. In that case I have no problem with foam benind the two layers of 5/8 drywall with green glue sandwich. applied directly to the studs. Interior partion walls need either clips and channel or double wall framing with the top plate built one inch short and IB3 clips to secure. The ceiling will need clips and channel and again if he wants to put foam behind the double layers of 5/8 I have no problem. Two layers of 5/8 in mandatory, three layers is better. If he thinks he has a better idea he is blowing smoke.
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post #9 of 14 Old 10-15-2018, 07:09 PM - Thread Starter
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How should I instruct him to secure the riser to the wall(s) if it is, if the walls are dry walled first?
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post #10 of 14 Old 10-15-2018, 07:20 PM
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gravity, properly built with 2x material and double or triple layer decking, it isn't going anywhere.
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post #11 of 14 Old 10-31-2018, 01:59 AM
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Does anyone know of a good HT contractor , I live in Los Angeles California. I'm not the handy type nor do I have the material and equip to build one from the ground up.
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post #12 of 14 Old 10-31-2018, 06:56 AM
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Contact MikeLA here on the forum, his personal theater was a featured theater of the month. He is in the LA construction game and might have some ideas in his Rolodex

His theater is the event horizon
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post #13 of 14 Old 11-06-2018, 06:29 PM
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Quote:
Originally Posted by BIGmouthinDC View Post
your contractor is full of crap. Containing low frequencies requires mass dampening and isolation his proposed design doesn't have it. Here is my talking point when I meet with contractors


Contractor construction notes
High Performance Home Theaters

Building a Drywall sound isolation shell

Four principles of sound Isolation are utilized:

MASS - ISOLATION-ABSORPTION-DAMPENING

  • Loose fill insulation in walls and ceiling
  • two layers of 5/8 heavy drywall
  • Green Glue dampening compound between layers
  • Drywall installed on a clip and hat channel isolation system with 1 1/4 and 2 inch long screws for first and second layers respectively
  • Clips and channel spaced per vendor specifications, no more and no less. Clips staggered on all available studs and joists, additional studs will be required in all inside corners for adjacent clip clearance.
  • Channel is 25 ga 7/8 inch tall furring channel (Hat channel) do not use 22 ga
  • Install drywall in sequence that results in a cascading joints and overlapping seams. First layer ceiling, then first layer walls, second layer ceiling, second layer walls.
  • Every hole cut in the drywall shell needs to addressed with a backer box, a putty pad, acoustical caulk or by other means. This includes items such as outlets, switches recessed light fixtures, in-wall speakers. Where possible these items will be installed inside the theater shell by passing wires through small holes which caulking around the holes.
  • Items such as seating risers, stages, soffits will be built after the drywall shell is constructed unless they are required to hide piping or ducts. In those cases the covering of the soffit will be the same construction as the sound isolation walls and ceiling.
  • If walls are non load bearing frame the walls one inch short to the ceiling joists and securing the top plate with IB3 clips spaced at the end of the walls and every 48 inches. Add additional clips above the hinge side of door framing. This will improve vibration isolation
  • Consider double wall framing or staggered studs for critical walls where sound isolation is critical, bedrooms, stairways etc.
@BIGmouthinDC , Awesome post and hugely informative! One question: in the red text quoted above, are you A) referring to additional IB3 clips to support the hinge side of the door frame in a non-load-bearing wall? Or, B) referring to added clips for the channel that supports the drywall in the area of the door hinges?


Thanks,
Mike
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post #14 of 14 Old 11-06-2018, 07:09 PM
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I'm referring to isolated framing built one inch short with the the top plate anchored in place with IB3 clips at the top, if there isn't a clip near the king stud for hinge side of the door add one and adjust the spacing of the others so that you don't have too many.
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