Does Soundproof Drywall Really Work?

Sound-Dampening With QuietRock

Installing drywall In a room
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If you have ever had problems with intrusive noise from next-door neighbors (or been on receiving end of complaints from neighbors about your noise), you may be interested in techniques for soundproofing your home. There are several ways this can be accomplished, ranging from simply installing a double layer of ordinary drywall to using special framing methods and insulation methods that reduce the sound transmission rating of the walls.

Recently, though, a variety of sound-dampening drywall products have become popular as a means of reducing sound transmission. They can be very effective at adding soundproofing to walls where it is not practical to reframe or use other structural methods. 

There are several brands of soundproof drywall available, but the best known is QuietRock.Other brands include CertainTeed's SilentFX, and National Gypsum's SoundBreak. Some building experts claim that QuietRock and similar products can produce sound dampening qualities equal to eight layers of standard drywall. 

Composition of Soundproof Drywall

Traditional drywall panels consist a layer or rigid mineral gypsum sandwiched between layers of paper. This tight, dense layer is actually quite a good conductor of sound, and soundproofing a wall constructed with standard drywall requires other framing adaptations, such as building extra-thick walls and filling the cavities with insulation, or installing sound-dampening sheets behind the standard drywall.

 

Soundproof drywall panels, including QuietRock, use an inner layer consisting of gypsum, viscoelastic, and ceramics, which makes them much more resilient and less able to transmit sound waves.

The QuietRock Product

The current owner of QuietRock, the PABCO corporation, says that QuietRock was the first such sound-dampening panel on the market, introduced in 2002.

The current entry-level product most suitable for DIY installation is product #510, carried by Lowes Home Improvement centers. It comes in 8-, 9-, 10-, and 12-foot-long panels, and is cut and installed in exactly the same way as traditional drywall. Additional products offered by the company include: 

  • QuietRock EZSnap: designed with a special paper that easily scores and snaps.
  • QuietRock EZSnap mold resistant: uses a non-paper facing that can't harbor mold
  • QuietRock 530: a 5/8-inch thick version, used where fire-resistance is required
  • QuietRock 530 RF: A radio-frequency (RF) shielding version of drywall, 5/8-inch thick 
  • QuietRock 545: the top-end product, used in commercial settings, such as theaters and recording studios. 

QuietRock products use a three-layer design: two layers of gypsum drywall about 1/4-inch thick, sandwiched around "viscoelastic sound-absorbing polymers" in the middle. In crude terms, this middle layer can be thought of as rubber, though it is more accurately defined as a viscoelestric material that dissipates energy and sound waves much better than any synthetic rubber or polymer. It is a special material that combines the elasticity of rubber with a viscous (sticky and thick) quality.

Elastic + viscous = viscoelastic

Evaluating Soundproof Drywall

Drywall panels, both sound-dampening and conventional, are rated for Sound Transmission Class (STC). Higher STC numbers mean better sound-proofing. But it is important to note that STC ratings are not for single panels, but rather a rating for an entire wall construction system including the surface panels. This means two layers of soundproofing wallboard, framing studs, and insulation. While soundproofing drywall panels are all inherently better than standard drywall at resisting sound transmission, it is not until these panels are integrated into a complete wall system that the true benefit is enjoyed. 

Look at how QuietRock compares to a typical interior wall constructed with conventional drywall:

 QuietRockDrywall
Wall AssemblyOne layer 1/2-inch QuietRock® 510 gypsum panel applied vertically on each side of 2 x 4 wood studs. Glass fiber insulation (3 1/2-inch thick) is installed in the stud space. 1 /2-inch CertainTeed drywall (one layer) on each side of 2 x 4 wood studs. Mineral wool insulation (3 1 /2-inch thick) is installed within the cavity. 
STC Rating5234

 

What About Multiple Layers of Standard Drywall?

QuietRock and other soundproofing drywall products make claims that a single layer offers a sound-transmission barrier equal to as many as eight layers of standard drywall. It is, therefore, theoretically possible to achieve good soundproofing with multiple layers of standard drywall. But eight layers of wallboard would be roughly 4 inches thick, leading to a host of issues: 

  • Increased weight on your walls and ceiling
  • Added cost
  • Receptacles need to be bumped out
  • Floor space is lost
  • Higher labor costs
  • Higher ancillary materials cost (joint compounddrywall tape, etc.)

Put simply, it is just not practical to think that multiple layers of standard drywall is a viable solution to  improving the soundproofing quality of walls. 

Costs and Bottom Line

Currently, the cost of QuietRock 510 at Lowes is about $54 per sheet of 1/2-inch-thick, 4 x 8-foot panel. This compares to a sheet of conventional 1/2-inch-thick drywall selling for about $7.50 per panel. This means that you can purchase roughly 7 sheets of standard drywall for the cost of one QuietRock panel. But if sound transmission is a serious issue for you, the extra expense might well be worth the investment, especially if quiet is very important to you. Installing QuietRock or another form of soundproofing drywall might well be an excellent choice for bedrooms, for example.