I have a client that lives directly adjacent to a busy highway in Southern California- the 605 Northbound for those from the area. They want to add a family room into the backyard facing the freeway. Here in So. Calif., 2X4 walls are typical, but I was thinking of framing it 2X6 for added for added insulation. Do thicker insulated walls deaden sound any?
I was also considering doing the alternating 2X4 stud on 2X6 plate method where the outside skin (stucco in this case) is separated entirely by airspace fom the inside drywall skin. I’ve never built one like this before, but I guess you do have to use a full depth stud (2X6) at the door and window openings. Does the benefit of these walls outweigh the added cost, labor and trouble?
Also, can sound deadening board be added- perhaps under the drywall? Does it help that much?
Lastly, what do you guys think I could do with the stucco covered walls that remain? Can you add an airspace to an existing 2X4 framed wall?
By the way, for those of you who were about to suggest a solid-grouted block wall, that’s already been done by the city (or Cal-Trans, I think). They call them “Sound Walls”- about 15′ to 20′ high slump-stone block walls along side the freeway shoulder and that wall becomes the back wall of these houses’ properties. In my client’s case it’s 35′ from the end of the house. That’s how close they are!
Thanks!
Replies
I've been pleased with the performance of offset stud walls I've done. In my own house to separate a bedroom from an office and in a student co-op around a public phone. Yes, I'd use windows and doors for 2x6 walls. Is it worth it? It would be for me in that situation but heck, I moved 2000 miles to get into the woods.
You gotta go double pane windows throughout before doing anything else. Maybe even triple pane - anyone have an assessment for the difference in sound transmission? Theoretically, it ought to help, just like it does for heat transmission.
Get some fast growing trees planted. They'll help with the sun, heat AND noise when they grow.
My understanding of sound deadening is that mass is more important than dead air space. The offset 2 by 4 on a 2 by 6 plate is used primarily for heat insulation. I'm sure it would help some for sound. I think you would be better to try some other things like, 5/8 drywall and res bar. We use res bar in offices and apartments to deaden sound. Res bar is horizontal strapping over the framing so that the board is attached to the res bar , not the studs. A split wall with dense board sandwiched in the middle can be effective. We use Homosote brand, it's like donacona, or buffalo board. It is just cheap, dense material.
As for the stucco, Is it the existing wall that will become an interior wall after the addition? If so, I'd tear it out. Unfortunately it becomes landfill. I guess you could furr it and dry wall over top. You would be losing some space though.
Smaller window opennings, heavier glass in the thermals, solid wood window frames, foamed into place. These will do a lot more for sound attenuation than most other means.
Masonry on the outside. Foam insulation on the inside of the wall cavity. 2 layers of drywall on the inside, overlapped.
Install of the above on a deserted island and your off to the races.
Gabe
Thanks for the responses everyone. I like the idea of smaller windows and the use of res bar for the drywall. This, along with the off-set studs should do the trick.
Now, I just want to confirm the method of framing off-set studs. The way I was thinking of doing it was to do a 16" OC layout for the inside of the plate and then another one shifted down about 2 1/2" for the outside of the plate. This, of course, doubles the number of studs. Is this the way to do it? I can't see any other way o get 16" OC studs on both sides.
Thanks!
We often lay 16 OC from the inside of the plate for the interior side of the wall and 16 OC from the outside of the plate for the exterior side.
For interior walls (both sides), I've done 24" O.C. 2x4s and stepped up the drywall to 5/8". Everything is 24" O.C. exterior around here for the lower heat conduction.
David Thomas Overlooking Cook Inlet in Kenai, Alaska
Your in SoCal? I would hire an Accoustic Engineer. For my projects I use Meno Scientific in Topanga, and they will come out, and spec the framing, glass, and finishes for you. First class people, first class job. Say hello to Neal for me.
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927
Thanks for the tip on the engineer- I never thought of that one!
If you are in Malibu, he is in your area too.Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927