How thick do walls have to be to be soundproof?

With noisy neighbors all around, are you looking for ways to get soundproof thick walls? Are you wondering how thick walls have to be to be soundproof? 

According to experts, there is no simple solution to this. They claim that a wall’s thickness is only one factor in soundproofing, and a lot more is to consider. 

Soundproof walls can be built with a typical stud wall constructed perfectly. It contains two layers of drywall/plasterboard and one air cavity between five and six inches deep. To completely soundproof a cemented wall, it should be a foot thick.

To understand what all goes into soundproofing walls, it is first important to understand the various aspects that surround them.

How thick do walls have to be to be soundproof?

The average thickness of a cavity wall constructed from a wooden frame and two pieces of drywall is 5 to 6 inches. It is called the air cavity inside the center; however, the bigger this cavity, the more effective the noise absorption, particularly at lower bass frequency. 

If you have the choice, a solid cemented wall can work miracles for soundproofing walls. In this scenario, a wall roughly one-foot thick would be ideal because it will effectively muffle all noises.

However, it is evident that a foot-tall, thick cemented wall is not always the best option. While you can surely consider the above-mentioned construction ways, thickness alone is not enough. A vacuous stud wall won’t do much to block noise since the air cavity space is the perfect spot for sound propagation to magnify and reverberate, which increases noise.

Therefore, you should focus more on constructing the wall perfectly rather than its depth. The major attention should be on adding insulation to the cavity inside, followed by separating and sound damping.

Things to avoid while working on soundproofing thick walls:

  • A phenomenon known as the triple leaf effect will result if resilient sound clips and/or channels are placed over existing walls.
  • Green Glue’s damping composition outperforms factory-damped plasterboard/drywall. Factory-damped drywall is far more costly and tough to install. Green Glue is simply easier to apply and is installed on sturdier walls because of its superior compound. Check out this 5-gallon tub available on Amazon
source: hushcitysp

Factory damped drywalls contain a ready-made layer of sound damping compound in the center of the drywall panel.  510 (1/2″) and 530 (5/8″) is the most common variant while you may find other variants with different thickness options.

There are two options I would recommend:

  1. QuietRock 510: which is 1/2″ thick and delivers STC ratings of 47-52. Costs around $50 to $55 per 4×8.

quietrock 510 stc ratings
source: QuietRock

2. QuietRock 530: which is 5/8″ thick and delivers STC ratings of 52-74. Costs around $105 per 4×8.

source: QuietRock

Ways to Soundproof Thick Walls

  1. Adding Mass

The most efficient approach to soundproof walls is to add more mass which increases the wall’s bulk. It absorbs and blocks sound waves and also makes the wall bulkier and less likely to shake.

But whenever thickening a wall, do keep in mind the area of the room and do not add thickness to the walls unnecessarily. Because with every inch increase in the wall you are also reducing the space within your room.

  1. Insulating wall cavity

It is possible to increase the wall’s soundproofing performance without losing any space by installing insulation in the wall cavity. It doesn’t increase the wall’s thickness, but it does deal with its major flaw: the vacant wall cavity.

Sound waves can travel freely inside a vacant wall cavity. It gets a passage to pass through the plasterboard, and once inside the walled chamber, it bounces off the flat surfaces, amplifying itself.

Insulating a wall cavity is thus one of the best ways to soundproof a solid wall, as the vacant cavity is filled with something solid. The ideal material to use is specifically designed soundproofing insulation, often made of fiberglass, which is easy to install. You can also read this detailed study about how an elliptical cavity can have an effect on the application of soundproof ventilation units.

  1. Decoupling

It is one of the best methods for soundproofing walls. Here, each side of the walls is separated/ decoupled to stop vibrations from traveling, and if there is no vibration, no sound waves can exist.

Decoupling can be done to thicker walls because you will have to construct two pairs of studs (each side of the wall will have one stud). If the walls are thick and wide, it would undoubtedly be beneficial. 

However, there is no perfect thickness or depth for soundproofing a wall, so try to build it as thick as you can by least affecting the space inside the room. You can read this amazing article from Soundproofcow on “How to Decouple a Wall?

soundproof a wall
  1. Resolve the issues

The weakest points of the walls are the doors and windows, which need proper attention and must be addressed in addition to the walls. Even if you build a wall three feet thicker, which is soundproof, you will still require the windows and doors which often have a maximum allowable thickness. 

For instance, standard interior doors typically measure around an inch or two, and they typically maintain windows as slim as possible to maximize visibility. It is essential to tackle these areas since they will always exist, irrespective of the thickness of your wall.

Misconceptions Regarding Soundproofing Walls

Before you spend your hard-earned money, be cautious of inept “soundproof” building materials such as: 

  • Soundproof Paint
    Many soundproof paints claim to deaden or soak up semi-noise transmissions, however, they can surely cover faded spots or nail holes on the wall, but no soundproofing. The thickness of the paint is only 30 thousandths of 1 inch. It is incapable of reducing the noise at the low and high edges of the frequency spectrum.
  • Soundproof Wallpapers
    Most soundproofing wallpapers are often regular wallpapers that are supported with a thin layer of foam or another noise-canceling material. They can be quite ineffective while controlling both high and low-frequency acoustic signals.
  • Wall Carpets
    If you place carpets on walls, noises won’t be stopped adequately unless you’re looking for the electronic or “shabby chic” aesthetic. Although a carpet might help to some extent with reverberation, it lacks the thickness needed to reduce sound transmission.

Conclusion

A reasonable starting point for soundproof walls is six-inches thick, but there are additional factors to consider. Focus on using the space properly in more useful ways, such as adding insulation to the wall cavity or decoupling. Because the thicker the wall will be, the smaller your room would look.


FAQs

  1. Which walls are the most soundproof?

Sound-absorbing drywalls are considered to be the most soundproof. Airborne noises cannot pass through drywalls because of their mass and thickness, which increases the overall volume.

  1. What are the materials used for soundproofing walls?

Mass-loaded vinyl, plasterboard/drywall, soundproofing gypsum, timber frame, fiberboard, cement, or rubber are examples of materials that can be used. Depending on the different thicknesses and densities, these soundproof materials can reduce a wide range of frequencies.

  1. Is thicker plasterboard/drywall better for soundproofing?

Greater bulk and stronger soundproofing are both correlated with greater thickness. Hence, plasterboard/drywalls are better for soundproofing.