Concrete is commonly used for building commercial spaces and multifamily homes due to its durability and strength, but when it comes to soundproofing, it isn’t as tough as you might think. While concrete is better at blocking airborne sound than materials like wood or drywall, it has its drawbacks when it comes to impact sound and acoustics. So, let’s talk about the pros and cons of using concrete for soundproofing and explore some solutions.

THE TOUGHNESS OF CONCRETE

Before talking about soundproofing, it's important to distinguish between sound blocking and acoustics. Sound blocking refers to a barrier's ability to stop sound from transmitting from one side to the other. Acoustics refers to the sound quality within a space.

Concrete is about as dense and solid as a building material gets, and you won't find a better base material for blocking sound. But as you explore its soundproofing ability, you'll come to find that even concrete may need more to effectively block sound, and it WILL create echo and reverb issues.

Strengths

So, are concrete walls soundproof? Not entirely, but concrete is better at blocking airborne noise than just about any other building material, particularly when it's plastered. For instance, a 3-7/8” wall made of autoclaved aerated concrete blocks can have a Sound Transmission Class (STC) rating of 38, which is a step above even a well-sealed, 1/2" drywall wall with wood studs and insulation (STC 33).

If it's hollow or filled and the thickness of the concrete play a significant role in its sound-blocking capabilities. That said, it’s essential to be aware of potential problem areas that can allow sound to pass through such as gaps, cracks, and openings around electrical outlets and plumbing.

Weaknesses

As previously mentioned, concrete is actually a great base point for blocking airborne sound, but when it comes to acoustics, concrete is the worst. To give you context, plain cast concrete reflects about 98% of all sound that hits it. Yikes!

On its own, concrete is not effective at stopping structural noise, such as footsteps or moving furniture. Low-frequency sounds like bass from home theaters can even cause rebar within the concrete to vibrate. Concrete's rigidity allows vibrational energy to transfer fairly easily, giving it a low IIC rating, which shows how well (or not well) a floor assembly reduces impact noise. For example, a 4-inch concrete slab typically has an IIC of 25, a 6-inch slab is about 27, and an 8-inch slab reaches 32.

How to Soundproof Concrete

One of the biggest challenges with any concrete space is the echo and reverb created. With nearly 100% reflectance, adding enough absorptive material into the space must be part of any concrete soundproofing project.

That aside, reducing noise transfer between spaces is a bit different. Here are some helpful concrete soundproofing solutions.

Soundproofing Concrete Walls

When soundproofing concrete walls, there are a few approaches to reducing airborne noise. The key is to isolate the concrete wall from the room’s wall. One of the most common approaches is simply studding out the wall over the concrete. Put some batt insulation between the studs then install your drywall. You can even take it a step further by double-studding the walls or staggering the studs.

Another practice is installing drywall with the use of resilient channel. An excellent way to soundproof a shared concrete wall is with resilient channel on one side holding drywall and the other side with RSIC-1®, resilient channel and 5/8” drywall, you’ll have an STC 56, which is a very high performing wall assembly.

Ensure all gaps around wiring or electrical outlets are sealed to prevent sound leaks, which can compromise your soundproofing efforts. Button up the job by adding absorptive materials to control echo and reverb. For soundproofing rooms like home theaters in basements, consider adding bass absorbing materials to the room.

Soundproofing Concrete Floors

For soundproofing concrete floors, you’ll need to solve for impact noise. Depending on your situation, consider solutions on both the floor side and ceiling side. On the floor side, use UnderBlock™ rubber underlayment (or UnderBlock HD™ for unfinished ceilings) to effectively reduce impact noise by creating an isolation layer.

On the ceiling side, one option is to wire hang a drywall grid and install insulation, which gives you a finished ceiling. Use RSIC-WHI® isolators on the wires to reduce impact noise transference. Alternatively, you can install a sound isolation system directly into the concrete using RSIC-1® ADM, which enhances the soundproofing effectiveness by decoupling the ceiling from the concrete structure.

For more help with soundproofing concrete floors, check out our article!

Is Concrete Good For Soundproofing?

Concrete has its strengths in blocking airborne noise, but it struggles with absorbing sound and stopping vibrational impact noise. Its density and thickness can work to your advantage, but the key is to combine concrete with other soundproofing methods to address its weaknesses.

If you're considering concrete for soundproofing, weigh the pros and cons carefully, and reach out to a Second Skin professional to help you navigate these options with personalized advice and high-quality soundproofing materials. Together, we can make your project sound as good as it looks!