All About Underlayments: Purpose, Benefits & Install Tips

May. 20, 2024

All About Underlayments: Purpose, Benefits & Install Tips

Underlayments play an important role during the installation of new hardwood flooring or laminate flooring. Whether you intend to staple down, nail down or float, an underlayment offers a slew of benefits during and after installation.

Staple or Nail Down Installation

With a staple down or nail down installation over a wood subfloor using solid flooring or engineered flooring, it is recommended that an underlayment of 15lb. black felt paper is rolled out over the wood subfloor prior to installing the new floor. This hardwood felt paper is necessary to greatly reduce the chance of any moisture coming up through the subfloor and will help protect the new hardwood flooring. Even if you think you don't need it and you're tempted not to use it, it's always better to be safe than sorry. Especially when being sorry could mean $1000's in damage. 15 lb. black felt paper is relatively inexpensive and can be the difference between warped hardwood flooring boards in the future or a floor that stays perfectly beautiful for a lifetime.

15lb. black felt paper for flooring installations over wood subfloors looks a lot like roofing paper, but it is very different. Roofing paper is typically coated with asphalt or tar, which will emit harsh chemical odors, especially if enclosed in your home. Therefore, it's important to make sure the 15lb. black felt paper you're using is manufactured specifically for hardwood flooring installations.

Installation of 15lb. black felt paper is incredibly easy and fast. Simply roll the black felt paper out over the plywood subfloor, overlapping the seams approximately 4 to 6 IN. and then use a hand stapler to attach to the subfloor.

Floating Installation

Underlayments pads are especially important for engineered floors or laminate floors which are installed via the floating method over wood or concrete subfloors. When you float an engineered or laminate floor, none of the boards are actually attached to the subfloor. An underlayment is necessary for multiple reasons, floating floors will expand and contract, moving ever so slightly as a whole unit. The smooth surface of the underlayment allows the flooring on top of it to move slightly during seasonal relative humidity changes. Underlayments are also are used under floating floors to act as a cushion, allowing for a bit of a softer feel when walked upon.

Some underlayments pads these days are made with an attached plastic moisture retarder. 4-6 mil Plastic moisture retarders are basically non-negotiable when it comes to installing over concrete subfloors, we always recommend the use of a moisture retarder over concrete subfloors. (For underlayments without a moisture barrier attached, you can always install a 6mil plastic sheet separately directly over the concrete slab.)

Underlayment pads also helps to even out subfloors which may have minor imperfections, which is important for a smooth floating installation process.

Lastly, some underlayments pads have exceptional sound absorption properties and can be used as a sort of sound insulator, preventing sound transfer.

There are a multitude of underlayments available for floating installations. They range from simple foam pads to foam pads with a plastic moisture retarders attached to dense felt-like underlayments with remarkable sound absorption properties. Foam pads are typically thinner and their sole purpose is to add a little cushion. Foam pads with moisture barriers attached are also on the thinner side but also offer that moisture protection. The denser underlayment pads (usually a felt like material) are typically a bit thicker and offer more support and insulation because of there dense nature. Please note... that "Regular Carpet padding" is too thick and soft to use as an underlayment pad for any wood or laminate flooring and could cause the joints of the flooring to break when walked on.

Some hardwood and laminate manufacturers make their own underlayments for floating applications, which they recommend for use with their products. However, in most cases, any industry approved underlayment will get the job done. It's important, prior to installation, to read the specific flooring manufacturer's installation instructions. If they require use of their brand specific underlayment in order for their warranty to be effective, it's always a good idea to acquiesce.

Installation of underlayment for a floating floor is very simple. Underlayments typically come in rolls. After subfloor prep, simply roll out the underlayment. Many underlayments these days have self-stick overlap flaps for connecting multiple sections of underlayment together. If the underlayment you are using doesn't have these, you can simply use duct tape to secure the edge of one portion of underlayment to the other. (Some flooring manufacturers will sell seam tape, but, really, duct tape works just as well.)

is a dense felt-like material, using air-laid filaments. This product is renowned in the hardwood flooring industry as being one of the most advantageous underlayments for floating floors. Features of Silent Stride Underlayment include: sound absorption, moisture protection, minimizing of subfloor imperfections, insulation and anti-microbial properties. On top of all that, Silent Stride is pretty affordable when compared to similar products in its category (cork or rubber underlayments, which share some of the same properties).

One of our top selling underlayments (shown above) isis a dense felt-like material, using air-laid filaments. This product is renowned in the hardwood flooring industry as being one of the most advantageous underlayments for floating floors. Features of Silent Stride Underlayment include:On top of all that, Silent Stride is pretty affordable when compared to similar products in its category (cork or rubber underlayments, which share some of the same properties).

Cork Underlayment

Cork underlayments are certainly gaining popularity over synthetic underlayments in both residential and commercial settings. But, what are the major benefits of using a cork underlayment? Cork is a natural product from a renewable source. If you're looking to go more "green" with your home, cork underlayment is a step in the right direction. Cork underlayment also has superior sound deadening qualities more than most any other synthetic underlayments previously mentioned it also helps minimizing subfloor imperfections, adds a degree of insulation and has anti-microbial properties. Many homeowners with allergies love cork as it is naturally anti-bacterial as well as anti-fungal. It's important to remember that cork is naturally water resistant, but not waterproof. Therefore, a 6mil plastic moisture retarder is recommended under the cork for installations over concrete slabs.

Cork underlayments can come in a variety of thicknesses. We've found that the most popular are the 1/8 IN. thick cork underlayment (3mm) and the 1/4 IN. thick cork underlayment (6mm). The only difference is the thickness, the thicker 6 mm will give you twice the sound absorption if desired to lessen any noise when the floor is walked on. Cork underlayments can come in either rolls or sheets. If an installer needs to add height to a subfloor, he'll often choose to use the thicker 1/4 IN. cork underlayment, as most synthetic underlayments measure up at about 1/8 IN. thick.

Cork underlayments are a bit different from other underlayments, because they can be used in staple/nail down installations, floating installations and even in glue down installations. If you plan on installing your flooring via a staple or nail down method with a cork underlyament, you can choose to either float the cork or tack it down to the plywood subfloor. For floating installs, you can either float the cork underlayment or you can tack it down to the subfloor; and then simply install the floating floor on top. If you choose to glue down your engineered hardwood flooring using a cork underlayment underneath you would need to glue the cork down securely to the subfloor and then you can glue the hardwood directly on top of that cork.

Laminate Flooring with Underlayment Attached

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By:

Steven

Date: May 10, 2022
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If we are installing solid oak hardwood floors on OSB subfloor do we need underlayment other than a simple plastic vapor barrier?

May 10, 2022

By:

RevW

Date: September 17, 2021
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Informative and useful, to the point

September 17, 2021

By:

Tony capili

Date: April 1, 2021
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Informationally good

April 1, 2021

By:

James Robinson

Date: March 19, 2021
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Thanks, I have been educated.

March 19, 2021

By:

Donnie

Date: March 15, 2021
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Im installing cork under nail down hardwood but Im hearing that it will crack overtime really bad. Is this true or not really?

Reply by HoskingHardwood: We have not had any problems with our cork underlayment. They use cork in 100 year old wine bottles without any problems.

March 15, 2021

By:

Mvr

Date: March 14, 2021
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5.0

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What can I put over top 6mm cork. I am told it is to flexible and click in Seams will break.

Reply by HoskingHardwood: We haven't had any problems with using a 6 mil cork underlayment under LVT its to firm to flex enough to cause problems with the thinner LVT. other softer underlayments are not recommended.

March 14, 2021

By:

Matt Early

Date: November 23, 2020
Page Rating: (

5.0

) Comments:

Your article was very helpful I am currently installing hardwood over a wooden subfloor and also installing vinyl plank flooring over concrete subfloor. Your article address both issues and was very informative thank you

November 23, 2020

By:

Allan

Date: October 29, 2020
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5.0

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I’m about to install engineered hardwood flooring in an old post and beam home. Subfloor is 3”x6” t&g decking with 7/16” OSB screwed on top. Was originally going to use a floating floor but will be nailing it down instead. I Purchased the mfg’s closed cell underlayment with a vapor barrier ($600) but they say it can only be used w/floating floors. It’s about thickness of RamBoard and doesn’t seem to compress. I’d still like to use it for sound deadening but they recommend AquaBar B moisture barrier with nails. Nails going through either product will defeat the purpose as a true “moisture barrier.” Why shouldn’t this underlayment be used with nails/cleats? I see you recommended using cork with nails but I can’t return this underlayment and would like to use it if possible.

October 29, 2020

By:

Jim Brady

Date: August 5, 2020
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4.5

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Hi guys, I like the article and detail. Im looking to not remove my 40year old solid oak 9"parquet 3/8" thick that is black adhiesive glued down on slab. My wife would just like a different wood floor. We did pergo in our cabin over foam and is too clickedity clack loud. She selected a 3/8" hardwood that is hickory birch, 4", 7" wide. My plan is to 40grit sand and float with a fixall the only 20ft sq area that is 1/8" low. Then install 30lb flooring felt. The new floor has 1/8" bull nose, TandG and doesnt click/snap together. Must I 45 degree nail it down, (I dont think the oak will like it and slab is underneath). or instead use a 1/8" tooth trowel with adhesive. Floating it is my preference but it is a non snap floor. Would this be a bad choice and I must get snap together? Im fine with replacing the base and trimming doors. The only other thing is my kitchen is linoleum over slab. Im planning to use a liquid self leveler to get to the existing oak floor height then follow

August 5, 2020

By:

Bruce

Date: August 1, 2020
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5.0

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I was not aware of cork as an underlayment. After reading this article I will be using cork.

August 1, 2020

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