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IIC Ratings
Author: Sturgeon Christie
Last Updated: February 9, 2024
Read Time: 6 Minutes
IIC Ratings
Author:
Sturgeon Christie
Last Updated:
February 9, 2024
Read Time:
6 Minutes
Author: Sturgeon Christie
Updated: Feb. 9, 2024
Read Time: 6 Minutes
Impact Insulation Class is the acoustical rating used to quantify the amount of impact noise reduced by a specific floor-ceiling assembly. The IIC of a structure is tested over a standard frequency range, and then assigned a single number that best represents how well the assembly reduces impact sound transmission. An individual material will not have an IIC, because the rating system only makes sense in the context of a floor-ceiling assembly that will be reducing impact noise as a combined unit.
Impact noise occurs when two objects hit each other. The vibrational energy from the contact travels through the physical structure before being released and heard as noise. A common example of impact noise is the sound of people walking on a floor. The impact of the footsteps transmits through the floor-ceiling assembly and is heard by people on the floor below.
Having a floor-ceiling assembly with a sufficient IIC rating is absolutely critical for creating a productive and comfortable environment. As a baseline example, a floor that is just a 4” thick, reinforced concrete slab would have an IIC rating of 25. For multi-family housing, the national building code requires hard finished floors to have an IIC of at least 50. This is very achievable, but you need to use a proper assembly to get there. A high-performing floor-ceiling assembly that transmits very little impact noise might have an IIC rating of 60+.
Impact Insulation Class is the acoustical rating used to quantify the amount of impact noise reduced by a specific floor-ceiling assembly. The IIC of a structure is tested over a standard frequency range, and then assigned a single number that best represents how well the assembly reduces impact sound transmission. An individual material will not have an IIC, because the rating system only makes sense in the context of a floor-ceiling assembly that will be reducing impact noise as a combined unit.
Impact noise occurs when two objects hit each other. The vibrational energy from the contact travels through the physical structure before being released and heard as noise. A common example of impact noise is the sound of people walking on a floor. The impact of the footsteps transmits through the floor-ceiling assembly and is heard by people on the floor below.
Having a floor-ceiling assembly with a sufficient IIC rating is absolutely critical for creating a productive and comfortable environment. As a baseline example, a floor that is just a 4” thick, reinforced concrete slab would have an IIC rating of 25. For multi-family housing, the national building code requires hard finished floors to have an IIC of at least 50. This is very achievable, but you need to use a proper assembly to get there. A high-performing floor-ceiling assembly that transmits very little impact noise might have an IIC rating of 60+.
Understanding Different Levels of IIC Ratings
Alright, so we’ve hit the technical definition of an IIC rating and we know that there are some minimum requirements in the building code, but what do the ratings really mean?
With IIC ratings, it can be easiest to think of how likely you are to get a noise complaint on your typical apartment or condo. As general guidance:
- IIC 50+ - some people will complain, but not many (95% satisfied)
- IIC 55+ - very few people will complain (99% satisfied)
- IIC 60+ - nobody complains
Because of this, some condos, apartments and shared buildings have an IIC rating minimum above even the national building code minimum. The required IIC rating and STC rating is typically always somewhere in the 50-70 range. If a specific assembly has not already been spec’d into the project, we can help you determine one that will meet your needs.
With more constructions we work on, the IIC rating ends up being somewhere between 50 and 60. IIC ratings as high as 70+ are achievable when required, but typically requires carpeted floors in addition to our soundproofing materials.
Watch this video that succinctly explains IIC ratings:
The Best Ways You Can Improve Your Floor’s IIC Rating
Loud footsteps, moving furniture, jumping, and machinery from your noisy upstairs neighbor are all tough to ignore in your home or workplace. Not only can they drive you crazy, loud noise is known to cause stress, lack of sleep, and inefficient work. The best way to remove unwanted sound from your life is to have a soundproof floor.
We typically run into several different scenarios:
1. A new building is being built, and we need to hit a certain IIC rating. This is no problem, and we can help you determine an appropriate floor-ceiling assembly.
2. An existing building is considering renovations and needs to maintain a certain IIC rating. This is most common when updating older living environments from carpeted floors to hardwood or tile flooring.
3. A homeowner has a noise issue either between floors in their home or with the neighbor above them.
In all of these scenarios, the best possible option will be to treat the floor with our UnderBlock Rubber Underlayment. You can use it with just about any type of floor, and it’ll ensure your floor-ceiling assembly has an IIC of 50+. For your typical residential homeowner who needs to soundproof a floor, there’s no additional thinking that needs to be done – just get the 10mm thick version and install it. For new building construction, we can work with you to hit any IIC and STC rating requirements.
In the table below, we overview some basic IIC testing we’ve done with UnderBlock:
| Floor/Ceiling Construction | IIC Rating |
| 6” concrete slab - With wire hung ceiling, R-13, and 5/8” drywall | 42 51 |
| 6” concrete slab with 2mm UnderBlock and 5.5mm LVT - With wire hung ceiling, R-13, and 5/8” drywall | 51 59 |
| 6” concrete slab with 5mm UnderBlock and 5.5mm LVT - With wire hung ceiling, R-13, and 5/8” drywall | 54 64 |
| 6” concrete slab with 10mm UnderBlock and 5.5mm LVT - With wire hung ceiling, R-13, and 5/8” drywall | 55 64 |
If you are not able to access the floor above, decoupling the ceiling from the building’s structure with sound isolation clips is the only way to improve IIC rating. RSIC-1 clips have been tested in a huge number of wall and ceiling assemblies, and have proven effective over and over at stopping impact and airborne sound transmission. For impact noise from the floor above, these sound isolation clips are your only option for a ceiling soundproofing treatment. They are commonly compared to resilient channel, read our article on sound isolation clips vs resilient channel for more information.
There are a ton of varieties of RSIC clips, many of which we don't list on our website. Reach out to us for a quote!
| Good | Better | Even Better | Best |
| RC-1 Boost | RSIC-SI-X | RSIC-SI-1" Deflection |
Now You're a Soundproofing Pro
Now you know what an IIC rating is and have some of the most common types of floor/ceiling assemblies and their IIC ratings. IIC ratings are important when building and think about soundproofing a hotel room, office building, or any other type of large construction project. Whether you’re dealing with new construction or just wanting to know how to how to hear less of your noisy upstairs neighbor, soundproofing a room by getting the right IIC rating will help make your space comfortable and peaceful. For more like this, check out our article on soundproofing for beginners.