Hi all,

My wife and I have contracted Owens Corning to finish part of our basement. In the short run, this room will be used as my son's drum practice space; in the longer run, it will become the site for a bigger and better home theater. In either case, we have the problem of LOUD bass permeating the house, annoying everyone else.

The room will take up only part of the basement, so there are two areas of leakage of primary concern: the ceiling and the new dividing wall. We are currently negotiating with Owens Corning to get the LEAST "bang" for our buck. Since I know relatively little about acoustics, I need some advice.

CEILING: At present, the basement ceiling is completely unfinished. There is a space of roughly 9 1/2" (24 cm) between the bottom of the floor joists and the board underneath the wood floor above. Owens Corning has offered us two options, priced identically:

(1) A layer of R19 insulation in the cavities between the joists; beneath that, a resilient channel; beneath that, one layer of sheetrock.

(2) One layer of R30 insulation; beneath that, one layer of homasote; beneath that, one layer of sheetrock. No RC in this option.

Which option would be better, or should we ask for something else?

WALL: The Owens Corning wall is made of rigid fiberglass. On the side facing the room it is covered by fabric. On the back, there is nothing: it attaches to a metal frame. Because we are dividing the basement in half, one wall will be freestanding, and so we will need to attach some kind of sound barrier to the other side of the metal frame.

What kind of barrier on the far side of the metal frame would give us the "least bang for our buck"? Sheetrock? Homasote?

Many thanks for your advice!

In reply to:

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(1) A layer of R19 insulation in the cavities between the joists; beneath that, a resilient channel; beneath that, one layer of sheetrock.

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Now I may be off base here - been a long time since I was an insulator's helper, but we used to use R8 as sound damping material. (realize now that you're probably using engineered floor joists which have a deeper floor cavity, so this would make some sense!) RC, which has taken over from stiff metal furring bar works very well at minimizing vibration transfer (found this with a quick Google)

In reply to:

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(2) One layer of R30 insulation; beneath that, one layer of homasote; beneath that, one layer of sheetrock. No RC in this option.

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No channel, but homosote, which multi-purpose arenas still use as flooring material, both for it's sound damping and to protect ice/court surfaces. Homosote is really more to "soften" hard surfaces from my experience to reduce reflected sound waves, and not so much to be used to deaden and stop transfer of vibration.

I have no hard suggestion for you, but I'm kind of curious as to why they chose what they did for materials in these options.

Bren R.

Thanks for the feedback (and for the chart)! As far as I can tell from talking with the Owens Corning manager, the R19/RC/drywall is their standard basement system ceiling. (HVAC ducts, pipes, and beams below the joists are boxed out with pine--and yes, the space between the bottom of the joists and the bottom of the floor above is large, about 25 cm.)

The Owens Corning manager suggested the Homasote/no RC option, because we expressed concern that the "standard" ceiling would not dampen the sound enough. (The OC salesman had told us that we would need "extra sound deadening" for the ceiling on account of the drum kit.) The OC manager (different guy, of course) doesn't know any more about acoustics than I do--he said this option was suggested by his "technical experts," which could just mean a half-hour surfing the web.

What would you do in our place?

Again, my construction knowledge is a decade old... but I'd be inclined to use a spray-in insulation - either blowing wool (fibreglas strands), cellulose or possibly polyurethane foam - this stuff was just coming in as I was deciding construction wasn't for me - ie: the spray-in expanding foam (fibreglas bats are fast and cheap, but not very efficient, at either dampening or insulating).

Down from there I'd probably want to seal in the "dead cavity" with 5/8" fireguard drywall - perhaps with RC or furring between it and the joists? - at this point, you've got a space where bass goes to die... problem is, the drywall on the bottom is now acting as a drum skin... from there, I'd use RC between that layer of drywall and a second layer of 5/8" to minimize the amount of vibration transfered to the actual ceiling.

Having two layers of drywall like that shouldn't be too much more expensive, since the top layer doesn't have to be finished.

Used a similar technique for a condo wall at a buddy's place... before the treatment, he was well aware of his neighbours', er... libidos. Afterward, he heard nothing at all (which, after his wife left him, may have been a drawback, instead of a bonus! lost a cheap form of entertainment!)

Just my two cents, anyway.

Bren R.

I agree with Bren's general concept. It is a common application in other basement HT rooms that have been built with thought. The more layers you have between two rooms/areas, the more sound vibration will be dampened. Use 2 layers of drywall, plus insulation, the more dense the better.
The best solution of course is to build a room within a room but often that is too costly an option.

Our new basement HT has ceiling batting, plus the walls all around are filled with a common Revy sound insulation material (non-formaldehyde production). I skipped on the second drywall layer as i did not want to make the room "too" soundproof, just sound controlled. The results have been excellent.