Originally Posted by rabident
I also saw Green Glue company makes engineered drywall called SILENTFX. I didn't realize there was an alternative to QuietRock. It's basically 2 layers of drywall with the green glue already sandwiched between. Goes on like a single layer of drywall. I don't know the price, but I think anyone that's been through clips + GG + DD with their builder would appreciate the added simplicity. At that point it becomes clips & channel which most drywall crews are familiar with. No issues with 2 screw lengths and the dangers of using the wrong one (which I think is a real issue with drywall crews paid by the job and therefore going 200mph trying to get done and move on). For DIY, I am sure field assembly drywall (FAD) is cheaper and probably performs better. But if you're going to pay someone, you should factor in how well FAD performs on clips while bound to a stud.
The house is really coming along nicely. My wife (and I) give you a big "thumbs up" for the exterior stone work.
While this product category may have started with QuietRock, there are a handful of other companies that make alternatives. National Gypsum makes Gold Bond Soundbreak XP
and Suppress Products makes Sound Engineered Drywall (SED)
to name two. Although both have a viscoelastic constrained dampening layer, even the price of these "off" brands is phenomenally high vs. standard drywall and Green Glue.
As you point out, your contractor would really have to charge a very high finish rate for the two layers of 5/8" and manual application of Green Glue for the two assemblies to be equivalent financially. But since soundproofing is all about mass, two layers of 5/8" with a Green Glue layer in between will always win vs. a single layer of these integrated soundproof products - with the possible exception of QuietRock 545
I don't recall exactly, but even if you use two layers of the engineered products to get the extra mass, it is my understanding that the measurable difference between two layers of the engineered drywall and two layers of 5/8" with Green Glue is only a couple of STC points at best. Considering the HUGE upcharge of one vs. the other, it's not money well-spent. A local distributor was clearing out 5/8" Suppress drywall in 4x8 sheets at $46 per sheet vs. the typical $75. A 4x8 sheet of standard 5/8" can be had for only about $8. Even factoring in buckets of Green Glue and a professional contractor's time, it is still difficult to justify the huge differential despite the easier installation of a single layer of the engineered product.Edited by TMcG - 12/16/12 at 3:53am