Soundproofing Drywall: Best Types, Double Layer Techniques & STC Ratings

When people picture soundproofing, they usually imagine something exotic — foam-lined bunkers, weird acoustic panels, maybe some kind of special magic wall. In reality, drywall is doing most of the heavy lifting in almost every effective soundproofing assembly out there, and it is not the fancy specialty stuff either. If you are one of the many people who has spent an afternoon comparing regular drywall against products like QuietRock and wondering which one is actually worth the money, I have got you covered.

Come with me to explore the different types of drywall used in soundproofing, exactly how the double layer technique with Green Glue works, real STC ratings for common wall assemblies, and when a specialty product like QuietRock genuinely makes sense versus when it is just an expensive shortcut.

Key Takeaway: Two layers of standard 5/8" Type X drywall with Green Glue sandwiched between them will outperform a single layer of specialty "soundproof" drywall like QuietRock in most cases, and it costs significantly less per STC point gained. The damping compound between the layers, not the drywall material itself, is what does most of the acoustic work.

Drywall Types for Soundproofing

Standard 1/2" drywall — the baseline, not ideal for soundproofing on its own
Standard 5/8" Type X — the workhorse of nearly every serious soundproofing assembly
QuietRock and other specialty acoustic drywall — a convenience product with a real, if narrow, use case

Standard 1/2" Drywall

This is what you will find in most homes built to minimum code, and honestly, it is not a great foundation for soundproofing. At roughly 1.6 lbs per square foot, it simply does not have enough mass to block much sound on its own. If your existing walls are 1/2" drywall, that is fine as a base layer — you will just want to add to it rather than rely on it alone.

Standard 5/8" Type X

This is the one I recommend for almost every soundproofing project, and it is not close. Type X drywall is fire-rated (which is required by code in many multi-family and commercial applications anyway), and it weighs approximately 2.2 lbs per square foot — noticeably more mass than the 1/2" version. Two layers of 5/8" Type X with Green Glue between them gives you excellent combined mass and damping, and in my opinion it is the single most cost-effective soundproofing assembly you can build.

QuietRock (Specialty Acoustic Drywall)

QuietRock and similar competing products build a damping layer directly into the sheet at the factory, so a single sheet can approach the performance of a double-layer standard drywall assembly. The thing that I like about QuietRock is the thickness savings — you get a lot of the acoustic benefit of two layers in the space of essentially one. However, the cost per sheet typically runs 5 to 10 times higher than standard drywall, which means the cost per STC point gained is much worse than the DIY double-layer approach.

The Double Layer Technique: Step by Step

This is, in my opinion, the best soundproofing upgrade available to the average homeowner, and it is genuinely doable as a weekend project.

Confirm your existing wall. Most homes already have at least one layer of drywall in place. That becomes your base layer.
Buy 5/8" Type X drywall sheets sized to cover the wall area, plus 2 tubes of Green Glue per sheet.
Apply Green Glue to the new sheet in a zigzag bead pattern, working in sections small enough to finish within 15 minutes.
Press the new sheet against the existing wall immediately after applying the compound, before it has a chance to skin over.
Screw the new layer to the studs through both layers of drywall, using screws long enough to reach solid framing.
Tape, mud, and finish as normal. Once it is screwed in, this becomes just another wall to finish and paint.
Give it time to cure. As with any Green Glue installation, full acoustic performance develops over 7 to 30 days.

For an existing wall, this technique adds only 5/8" of thickness total, which in my experience is a small trade-off most people are happy to make once they hear the difference.

Common Assembly STC Ratings

Here is a table of real-world STC ratings for common wall assemblies, going from a bare minimum wall up to a serious, professional-grade decoupled system:

Single layer 1/2" drywall, wood studs, no insulation: STC 33
Single layer 5/8" drywall, wood studs, fiberglass insulation: STC 36
Double 5/8" drywall + Green Glue, one side only, with insulation: STC 43–46
Double 5/8" drywall + Green Glue, both sides, with insulation: STC 50–54
Isolation clips + double drywall + Green Glue + insulation: STC 55–60
Double stud wall + double drywall + Green Glue + insulation: STC 60–65

To put this in plain terms: at STC 33, a normal conversation on the other side of the wall is easily understood. By STC 50, you can generally only hear loud noises as a faint murmur. By STC 60 and up, you are approaching the kind of isolation professional recording studios aim for.

Why Two Layers Beats QuietRock on Cost-Per-STC-Point

Let's run the actual numbers, because this is where the double-layer approach really wins. A sheet of 5/8" Type X drywall typically runs $15–$20, and 2 tubes of Green Glue add another $30–$40, putting a double-layer sheet-equivalent cost somewhere around $45–$60 per 32 square feet (accounting for the existing base layer plus the added layer and compound). QuietRock, by comparison, often runs $70–$120 per single sheet for similar coverage, and you are only getting the equivalent of roughly one layer's worth of installation labor rather than two.

In my opinion, the double-layer standard drywall and Green Glue combination wins on cost almost every time, delivering equal or better STC performance for meaningfully less money. However, QuietRock does have a real use case, which brings me to the next section.

When to Use QuietRock Instead

If thickness is an absolute, non-negotiable constraint — for example, a tight closet conversion, a doorway with limited clearance, or a room where every quarter-inch of space matters — QuietRock's single-sheet-does-the-work-of-two approach genuinely makes sense. In those specific situations, I recommend it without hesitation, because the alternative (not soundproofing at all due to space constraints) is worse than paying the premium.

Frequently Asked Questions

Do I need to remove my existing drywall before adding a second layer?

No, and this is actually the beauty of the technique. You apply the new layer directly over your existing drywall, which is exactly what makes this such an accessible DIY upgrade compared to demolition-heavy soundproofing methods.

Is Type X drywall required, or can I use standard drywall?

Type X is not strictly required for the acoustic benefit — the fire rating is a separate consideration. However, since Type X typically costs only marginally more than standard drywall and adds a bit more mass, I recommend using it anyway.

Can I skip the Green Glue and just add a second layer of drywall for mass alone?

You can, and you will get some improvement from the added mass, but in my experience it is noticeably less than what you get with Green Glue in the mix. The damping compound is doing a lot of the real work here, so skipping it leaves a lot of performance on the table for a relatively small additional cost.

How much weight does double-layer drywall add to a wall, and is that a structural concern?

Two layers of 5/8" Type X adds roughly 4.4 lbs per square foot combined. For a standard residential wall on normal framing, this is not a structural concern, but if you are doing a large ceiling application, it is worth double-checking your framing can handle the added weight, especially on older structures.

Does painting or texture affect the acoustic performance of the assembly?

No, standard paint and texture have a negligible effect on sound transmission. Finish the wall however you like — the acoustic performance comes from the layers and the Green Glue beneath the surface, not the finish coat.

Final Thoughts

Drywall is unglamorous, but it is genuinely one of the most important materials in any soundproofing project, and getting the layering technique right matters more than which brand name is on the sheet. In my experience, two layers of standard 5/8" Type X drywall with Green Glue between them is the best value in soundproofing, full stop. Save the specialty products for the situations where thickness truly is the deciding factor, and put your budget toward doing the double-layer technique correctly instead.

Related Guides

If you found this guide helpful, I recommend reading these related resources to deepen your understanding:

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