making 2×4 wall thicker for sound insula
My bedroom has two exterior 2×4 walls. I like quiet, especially at sleep time. I’m thinking about adding on 1-3/4 (ripped from 2x4s) to the existing 2×4 structural wall to provide room for more insulation between the studs and to acoustically isolate the wall the drywall is on from the structural wall. I thought I’d put a piece of foam sill seal between the structural wall and the 1-3/4″ wall using a minimum number of screws to fasten the isoalted wall to the structural wall. This way only the screws will transmit vibrations through and the sill seal will help dampen other noises. I can then insulate it like a 2×6 wall, thereby getting more thermal and sound deadening insulation in the process. I thought about building a completely isolated wall, but believe it or not, that extra width will make a difference that will make windows off center etc…. Does anyone think my plan will be effective? Better ways?
Replies
I've done the same dance in designing home theaters, and I can tell you this, the main word is isolation. You will se a much better result if you can actually build two independent walls. A second choice option would be (to save space) to build the second wall with 2 x 3s and leave the back open.
I think Owens Corning makes special insulation geared to sound absorption.
Jake Gulick
[email protected]
CarriageHouse Design
Black Rock, CT
Here is another alternative. Frame with 2x6 plates and sills, but using 2x4s on 24" centers, in two alternating "layers," one against the outside walls, the other offset 12", with the edges to the inside. Insulate per normal methods. Use the RC channel on the inside, horizontally at 16" centers. Consider using 5/8" sheetrock instead of 1/2". Your studs won't be transmitting sound directly through, the RC channel provides additional dampening, and the 5/8" adds mass.
Mass actually does more for you than anything. Building your exterior walls of two spaced layers of 6" block, with an insulating core of vermiculite between, would really keep out the annoying vibes.
Good listening to you.
I thought of the old 2 x 6 trick, but it sounds as though the 2 x 4 wall is already built.
Two layers of 5/8" SR, completely isolated, via unique wall structures, is the biggest bang for the buck. Or should I say the quietest bang for the buck?
Resilient channel won't hurt either.Jake Gulick
[email protected]
CarriageHouse Design
Black Rock, CT
The floor system also matters. If you have a slab on grade, the 2x4 stud on 2x6 plate trick will work a lot better. I know of a professional drummer who built a "box within a box" practice room that way, to the complete satisfaction of the neighbors.
-- J.S.
They make a product especially for this situation. It is called sound resilient channel, or RC-Channel. Install it onto existing drywall, perpendicular to the studs, screwing it to the studs. Then you install drywall onto the RC-Channel with screws only to it. This produces a sound-deadening effect, and it is so much more cost and labour effective. Hope that helps. I've used this stuff on many condo's for the richer clients.
chuck.. sounds like a good time for a "Mooney Wall"
leave your 2x4 studs .. cross them with 2x4's ripped in half ,nailed horizonatally at 16" oc... move your elect devices to the face..
then either put up your drywall and blow dens-pak cellulose ..or..
use Insul-mesh and blow dens-pak cellulose..
you get mass, isolation, and great r-value
Mike Smith Rhode Island : Design / Build / Repair / Restore
The weak spot is not the walls, it's the windows. Even with a wall 'floating" in front ofthe structural wall (ideal, since this isolates the interior wall from exterior noise)--the windows are a single diaphram for conducting noise.
Now, you can get some relief from the windows, you just have to tought enough for some layered curtains (yes, this also means having to learn about 'soft furnishings" too . . . ) A pleated set of "blackout" curtains offer an excelent sound buffer (not just soft, but undulating--a bonus). Whether closed heavy curtains will pass muster with the "design comittee" is another matter altogether.
You could go 60s "retro" and line the entire wall with nice heavy curtains (it's a system the multiplex has been using for 20 years). Another hard sell to the design comittee, though . . .
I agree with capnmac on the windows. A good fix is interior magnetic storms. You can get them custom painted and they have an almost air tight seal. They are easy to install. Whats more once they are installed they are almost invisable(a bonus with the 'desighn comitte') I have installed them for clients just for the sound deadening benifits.
Consider a layer of 'sound deadening board', sold at most home centers.
Drywall over that. Simple and relatively thin.
All the suggestions here will certainly help. Simply adding a second layer of drywall right over the existing one will considerably dampen the sound. RC, channel will defiantly help. If you are looking for insulation for sound though, don't waste your time with fiberglass batt. See if you can locate a contractor that does rock wool, insulation. ( I think that's what it is called) I saw a demonstration on this stuff and it's sound absorbing qualities are awesome, (it's also fire proof) The guy put a wad of it in his hand and then proceeded to melt a penny on top of it with a blow torch! Pricewise I think it falls between blown in cellulose and Icyene.
I don't understand! I cut it twice and it's still too short!
man... my old boss invented that demonstration with cellulose insulation in about 1979.. right after 60 minutes had done an expose' ( flawed ) about the dangers of cellulose..
i bet you dollars to donuts.. cellulose is just as fireproof and sound insulating as rock wool... and a lot more pleasant to be around...
hell , i'd rather roll in fiberglass insulation naked , than work with rock woolMike Smith Rhode Island : Design / Build / Repair / Restore
Mike,
Is rock wool that bad? I've never worked with it, I just saw the demonstration...it looked pretty impressive.I don't understand! I cut it twice and it's still too short!
The rock wool I worked with in the long ago past was pretty treacherous - among the strands were small sections which were pretty much like obsidian shards - or thin long glass shards - which could make small cuts in the skin. The stuff used to be basically slag waste from blast furnaces that is blown into thin threads, so I don't know what kinds of impurities it would leave in any small cuts. Perhaps they have improved it over the last couple of decades, however.
Yeah I don't think this is the same stuff. The guy handled it with his bare hands, and he did mention that it's not the same stuff they used in the 60'/70's. They blow it in, like cellulose. You should check out the "new" rock wool, I was really impressed.I don't understand! I cut it twice and it's still too short!
man.... it's still the same basic material... just finer fibers and better quality control..
the problem is the fibers are almost identical to fiberglass insulation... and it reacts the same way as fiberglass.. it allows air penetration.. it will not absorb moisture vapor..
one big advantage it has over fiberglass is that it will not melt... which is what makes fiberglass useless as a fireretarder..
my old boss used to melt pennies at all the home shows with a handful of cellulose in his bare hands..
he had me build (3) 4x4 buildings and did a comparison burn of the three.. it was so successful, we built (3) 8x8 buildings and invited all the firemarshalls and TV stations to "the big burn"... cellulose was extrememly successful in protecting the structure from burning long after the other two structures were piles of ashes..Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike,
Have you used it at all? I'm just curious, I couldn't beleive how much it deadend the sound.I don't understand! I cut it twice and it's still too short!
no... i've moved truckloads of the old style...
wanna see a bunch of grown men whine ?
tell 'em you're next job is in an attic with rockwool...
most blown insulation has very good sound control characteristics , so i believe you that blown rockwool is a good sound insulator.. so is dens-pak celluloseMike Smith Rhode Island : Design / Build / Repair / Restore