Decouple Walls From Floor Joists. - Carpentry - DIY Chatroom Home Improvement Forum

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Old 11-02-2009, 12:04 AM   #1
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Decouple walls from floor joists.

Ok, i know that the post subject sounds confusing but it really isn't. I'm currently beginning to remodel my basement and just got the vapor barrier installed and will be starting to frame everything up soon.
It is going to be a home theater and play room so i want the maximum sound proofing that is reasonable affordable. For the ceiling this means two layers of 5/8 drywall with green glue in between them but I am wondering about the walls. I don't really want to hang tons of 5/8 rock on the walls and I'm worried that if I attach the top plate to all the floor joists I am worried that vibrations will be transmitted through the floor joists and into the upstairs.

I had thought that I could somehow just leave a 1/4 inch or so between the top plate and joists and just attach a couple straps every 4' or so from the top plate to the joists. This would decouple the wall from the floor joists.

Just thought I would throw it out there and see what you guys thought. BTW, the bottom plate is bolted to the foundations with red heads. (not that helps the lateral stability a whole lot but some) .



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Old 11-02-2009, 12:11 PM   #2
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just got the vapor barrier installed and will be starting to frame everything up soon.-------- Read this on vapor barriers:

Put a strip of backer rod between each joist and the wall top plate: Use the thickest available.
I hope you used a capillary/thermal break under the pressure treated bottom plate and spaced it from the rigid foam board (with sealed seams) as in the article.
Be safe, Gary


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Old 11-02-2009, 01:34 PM   #3
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I understand pretty well about vapor barriers and moisture management but did not install any insulation under my bottom plate. I decided against foam board for a number of reasons so moisture management for the basement remodel is being completed through the use of 6 mil sheeting sealed to the top plate and base of the wall (and eventually on top of the slab under what will be my floor) with acoustic sealant. I insulated and sealed all the inter-joice spaces with 1" thick rigid insulation and foam (sealing and insulating the sill plate).

Not so sure that backer rod will give me the decoupling that I am after. Someone suggested to me that I screw the top plate into the sill plate. I would think that the mass of the sill plate (its a 6 x 6 with an entire house sitting on it) would dampen any vibrations pretty well. The other suggestion was attaching the 2x4's to the concrete foundation (poured not block) with brackets (although this would be a great deal more drilling or pheumatic nailing into concrete )

I have been googeling "floating walls" as this seems to be the correct terminology no?
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Old 11-12-2009, 05:17 PM   #4
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You can attach the top plate of the newly framed wall to the existing joists by using a decoupling clip known as the DC-04.

The reason that the side walls are built heavy and often damped is because much sound will easily pass through the single sheet of drywall and head straight up into the joists.
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Old 11-12-2009, 05:49 PM   #5
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Hi! I just did the same thing you are doing with the plastic and it caused condensation to form on the wall. This especially shows up in the summer time when warm air hits the cool wall or when you heat the basement room. I fortunately caught this before I drywalled and cut the plastic off. You really need to listen to these guys about vapor barriers below grade. You may not be seeing it right now cause the weather is cooler but the plastic will cause the wall to "sweat" and condensed water will run down it causing moisture and mold nightmares.
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Old 11-12-2009, 05:58 PM   #6
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Hi --Third vote against vapor barriers. Mold makers.


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