Basic Wall Questions

First of all, thanks for all the time you guys (and ladies) give up for the newbies among us. Now on to the question: -If two seperate rooms are built, would there be problems with the walls being sheet rock, MDF, sheet rock, studs w/insulation, sheet rock as depicted below? -If the layer marked Question Layer is unnessecary then how do you get the insullation to stay in the right place?

ribrecording wrote:

If two seperate rooms are built, would there be problems with the walls being sheet rock, MDF, sheet rock, studs w/insulation, sheet rock as depicted below?

Hello again... I don't see anything "depicted below" -- perhaps the image was larger than the alloted size. (If that happens, you see a warning message at the top of the page when you preview your post.) I'm sure a picture will be worth a thousand words... It's not clear to me whether you're talking about doing a room-within-a-room, or just trying to beef up existing walls. Either way, I see problems, as it appears to me that you're not following the fundamentals of soundproofing. If you're simply adding MDF and sheet rock to an existing wall, then you are effectively increasing the mass on one side of the wall without addressing the lack of a similar amount of mass on the other side. (Besides, multiple layers of gypsum (a.k.a. "sheet rock") is typically more effective and less expensive than a gypsum/MDF combination. If you're describing an entirely new wall that will run parallel with an existing wall, then you have described 3+ leaves, which will likely make things much worse. Be sure to follow the advice I posted for you on your acoustics thread. There is literally hours of study material in the posts that I referenced. Take it from me -- it's hours well spent. I'd much rather sit in front of my Web browser investing time reading the advice, facts, and accounts on this forum before I build, rather than spending the same or more time (and lots more $) building, then rebuilding, then rebuilding...

Rib, file size is max 150k - I find that jpg gives more accurate colors (if you care) and small enough file size. When I use Paint for illustrations, I save it first as 24 bit .bmp, then as a jpg - that way, any corrections will be done to the bitmap (less losses) and re-saved as a jpg for posting... Steve

.gif works great too when too much color correction in jpg.

Here is the graphic, sorry I thought it was a gif (I was wrong, as usual :) ). I got the idea for the MDF from the Egan Studio page, mainly so I could have walls of differing density (one room with two gypsum and one MDF and one with three gypsum). -So, does this still create a problem, and if will removing the "Question Layer" solve this? -Second, if removing said layer is advisable, then how do I get the insullation to stay put? Again thanks to all you guys for your advice!!!!

Both layers you labeled "question layer" should NOT be there - the far left and far right leaves, each shown with three layers, combined with the space and insulation between them, make up a proper mass-air-mass sound barrier. Adding ANY other non-porous layers, even a layer of paper, will reduce the effectiveness of the wall at low frequencies. One way to build this type construction is to build one wall first, insulate between studs, then nail fairly lightweight lath across the studs at approx. 2 foot intervals to hold the insulation in place. Then, you build the second wall laid down on its floor, adding the lath to the upside of that frame; then tip the frame into place, secure it with resilient mounts (sway braces) so it isn't hard coupled to your ceiling or the other wall frame, fill with insulation, and sheath with your three layers. Keep in mind that 3 layers each side is only as effective as the REST of your construction - ceilings and floors, doors, glass, HVAC, all are more difficult to build to high isolation than walls... Steve

What about thicker insulation batts in each wall that lightly compress each other, such as in my design? (I'm not trying to hijack this thread ;) -- I just think it might be a good idea, or maybe it's not a good idea and I need to make a change to my own! :shock: )