This is a question we get quite often here at Soundproofing America, How do I soundproof a wood floor to stop the transmission of sound to the people below. This is a very common issue in condos, co-op’s and apartments. Generally with a condo or co-op there are regulations called CC&R’s for which govern the amount of noise that can be transmitted from one floor to another. A very big concern with condo associations is the amount of impact or foot traffic noise which is transmitted through a wood or floor and down to the neighbors below.
In most condo or apartment situations, the upper units have installed carpet and padding. The reason for this is that these materials are soft and absorbent and will stop most the of the harsh foot fall noise that would otherwise transmit through a wood surfaced floor.
So, what do you do if you live in an upper unit condo or apartment and you want to put in a wood floor? Well I’m glad you asked. There are very effective floor underlayment’s which can be installed directly over top of your clean bare sub floor. Generally these soundproof floor underlay’s are made of high grade recycled rubber (basically recycled car tires) For some scientific reason, recycled rubber is quite effective at blocking unwanted foot fall noises from being transmitted through an normal wood structure floor assembly.
When looking at a soundproof floor underlay you will need to be concerned about 2 numbers or ratings. The first rating is the STC rating which stands for (Sound Transmission Class) this number refers to the amount of airborne sound that will be transmitted through your floor assembly. Sounds like TV’s telephones, stereos etc. These noises are much easier to combat than the Impact or foot fall noises that can be transmitted through a floor ceiling assembly.
The second and more important rating is the IIC rating which stands for (Impact Isolation Coefficient) this number tells you how effective a floor underlay product is a stopping foot fall noise from being transmitted through a floor ceiling assembly. The IIC number is the number that most condo and apartment associations are most concerned about. They want to keep the downstairs neighbors happy.
Now when looking for a high quality soundproof floor underlay you will need to consider the complete floor ceiling assembly. In other words what is in your assembly? Is there insulation between the joists? Is the ceiling down below floated on resilient channels or sound clips? Is the ceiling below 5/8” or thicker drywall? All of these factors added up give you the complete picture when you are looking for the highest STC and IIC numbers.
One good example of an effective floor underlayment is our UnderBlock Rubber Floor Underlayment soundproof floor underlay. This material is a 3/8” thick recycled rubber that comes in rolls that are 4’ wide X 25’ long. It has one of the highest STC and IIC rating of any soundproof floor underlay on the market today. It is the product we recommend most for both efficiency and cost effectiveness.
Now let’s talk about the installation of the UnderBlock Rubber Floor Underlayment . First of all we recommend cleaning the bare sub floor thoroughly before beginning the installation application. Once the floor is cleaned we strongly recommend applying a rubber to sub floor adhesive. One of the best is the DA-5 subfloor adhesive. This product comes in a 5 gallon can and is applied directly to your wood or concrete sub floor using a 3/16” notched trowel. After you have applied the DA-5 adhesive, you will then roll out the UnderBlock Rubber Floor Underlayment directly over top of the applied adhesive. You want the Impact Standard to cover the floor from wall to wall. If you are able to get this product up under the base boards, that would be great, but if not bring the underlay as close to the baseboard as possible. As you roll the Impact Standard out onto your floor, make sure that you butt all seams together tightly. It is a good idea to lay down a bead of acoustical caulk to the edge of the Impact Standard before you roll out the next roll, this will insure that this product is sealed at the butted seams. The next step would be to caulk around the perimeter of the soundproof floor underlay, this will help to block the airborne sounds from escaping to the floor below and visa versa.
Hey we’re almost finished. The next step is to lay down your wood or floor. One quick note, if your wood floor is a nail down wood floor you will need to glue a backer board directly over top of the Impact Standard so you have something to nail the nails into besides the rubber membrane. If you are putting down a snap together or an engineered wood floor then you can do so directly over top of the Impact Standard underlayment.
That’s basically the entire procedure for soundproofing a wood or floor. Keep in mind that if you are planning to install a marble floor we do recommend using a backer board to prevent the marble from shifting or cracking. This is simply a recommendation; many of our customers install their marble floors directly over top of the UnderBlock Rubber Floor Underlayment underlay.