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Soundproofing Existing Walls DIY & Buyers Guide

When building a home, most homeowners consider the number of rooms to add to the house. They also think of what these rooms will look like. Sometimes, they overlook the functionality of the room or the features they need to maximize the use of these areas. For instance, you need a soundproof room for a specific reason, but the house is already built. Are soundproofing existing walls possible? If so, which is the best one to use to make your room soundproof?

QuietRock Sheetrock

When soundproofing existing walls, one method to consider is the QuietRock. It refers to a sound damping product characterized by a viscoelastic material sandwiched between two gypsum layers. These gypsum layers can block soundwaves, while the viscoelastic material can damp the wave vibrations. When you combine these sheets, you can quickly decrease sound transmission in or out of a room by between 15 and 20 STC points. When using QuietRock, know that the sheets are available in thicknesses of 1/2″, 5/8″, and 1-3/8.” They can also have dimensions of 4’x8′, 9′, or 10-feet. 

QuietRock can also have its lengths which are tapered for taping and mudding. Not only that but they can also be scored and snapped the same as regular sheets. Compared to using Drywall, one of the benefits of using QuietRock is it provides better sound attenuation. Meaning, it reduces the need for additional layers, resilient or hat channels, and viscoelastic material. Not only that, but you can also save more since the wall can be finished in one pass instead of multiple passes for different layers of material.


Although QuietRock is a better option, Drywall is still one of the many options to consider when soundproofing existing walls. Drywall refers to the sheets of gypsum wrapped in paper and commonly have tapered edges on the long sides for tape and mudding. If Drywall is not a common name, then you might be familiar with it as it goes by the name wallboard, gypsum, gypsum board, plasterboard, and Sheetrock. Drywall is offered in various thicknesses, which is a good thing since these have specific uses and products. Take note that the thicker the materials are, the denser they are. Meaning, they can offer more mass which decreases sound transfer.

For drywall, here are several options:

  1. Blue Board – features more water and is mold resistant when compared to the Green Board. It is commonly used for plaster finishes because of its unique absorption properties.
  1. Green Board – it is a moisture-resistant gypsum sheet. Its green covering is more impervious to moisture. Although it is not waterproof, it is still ideal as a backer for tiles in bathrooms, kitchens, and laundry rooms.
  1. Paperless Gypsum – it is covered with fiberglass that can resist moisture, mold, and mildew. Since the fiberglass covering isn’t that smooth, you might need a slick coat of joint compound for a smoother paint finish.
  1. Purple-covered gypsum – this is quite similar to regular sheeting. However, it has a better moisture and mold resistance. Therefore, you can use it for basements or bathrooms.
  1. Type X – this is made of non-combustible material, but to make it fire resistant, it should have a 1/2″ thickness. This way, it can achieve 3/4-hours of fire resistance and a 5/8″ thickness an hour. Building codes require type X for specific locations, including apartments, schools, meeting rooms, and garages.

Soundproofing Existing Walls

When soundproofing existing walls, you need to consider the size and shape of the room. This is because larger rooms tend to produce more noticeable echo and reverb. As the sound bounces off a surface, it creates reflections that absorb or reflect onto other surfaces. Remember that the larger a room is, the longer the sound travels between each of these bounces. Meaning, it adds up to a longer time delay before the sound waves dissipate.

Besides size, the shape of the room should also be considered. For instance, high ceilings increase reverb time considerably while the parallel surfaces give the room significant resonance. That’s why you need to install acoustic panels effectively. Another essential factor to consider is the surface materials in the room. Ask yourself questions like:

  • Is the floor carpeted, or do you have hardwood? 
  • Do you have concrete walls, or are they drywall? 

Know that hard surfaces reflect more sound making a significant impact on the reverb time. On the other hand, soft and porous textures can absorb more sound, resulting in shortened reverberation time.

Spray Foam Insulation

If you are soundproofing existing walls, you might also need spray foam insulation. The spray foam refers to an open or closed-cell polyurethane material that is made of two components. They are mixed when sprayed onto walls or into wall cavities used to cover a surface or fill a crevasse or cavity before hardening. One part of this liquid spray is polymeric MDI (methylene diphenyl diisocyanate), while the other is a blend of polyol resins, fire-retardants, surfactants, and catalysts. Take note that the fire retardants decrease the combustibility and smoke generation.

Some homeowners think that soundproofing is not that important, but it is. This is because it offers a lot of exciting benefits than you could imagine. The best thing about soundproofing is that you can do it even if your house is already built. Soundproofing existing walls offer more privacy for all family members. For instance, you can sleep better since you’ll no longer hear the noise coming from the other rooms.  You’ll also get rid of the worries of being listened to in private discussions with your spouse or partner.