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All About Underlayments: Purpose, Benefits & Install Tips

by Crystal Hosking - Hosking Hardwood Flooring, Inc. ©2013, Copyright Protected. All Rights Reserved

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 humidty 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.)

 

One of our top selling underlayments (shown above) is Silent Stride underlayment pad 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). 

 

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

Some manufacturers, like QuickStep and Alloc, make laminate flooring with an underlayment already attached to the back of each board. This makes installation quick and simple, negating the need to roll out a separate underlayment. Just keep in mind that if this attached underlayment does not have a moisture barrier attached as well, it's always a good idea to lay one down prior to installing your new laminate floor.

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Overall Rating: 4.5 stars - 79 reviews

By:
Date: March 18, 2019
Page Rating: (5.0/5)
Comments:
Great information! I will be laying 3/8 plywood over my 1/2 " plank floor and will be installing either solid hardwood or engineered hardwood floor. Can I lay the 15lb black felt paper and then the 6mm cork over the felt paper? What is your opinion on those felt cushion underlayments.
Reply by HoskingHardwood :  Apply the black felt paper over the plywood first.  Cushion type underlayments are for floating floors. 6mm cork is firm enough to use with either types of flooring. 

 

By:
Date: March 9, 2019
Page Rating: (5.0/5)
Comments:
Awesome article! I had glue down engineered hardwood flooring that was replaced with a floating floor. Unfortunately, the new floating floor, including the new underpad, is 1.15 cm lower than the previous one. Our installer said they couldnt find any underpad that met the sound requirement that would have been the same size as the previous underpad. (IIC 65) Now we have multiple gaps due to the floor being lower, most significantly with the door frames. Basically, what Im hoping you can answer, is if the installer was able to do anything to match the height of the previous flooring to ensure there would be no gaps at the door frames.
By:
Date: February 8, 2019
Page Rating: (5.0/5)
Comments:
Woderful article very informative! I have an installation challenge! I need to float a 3/8 engineered floor over another hardwood floor and the boards will run the same direction? We want to also preserve the old floor without nailing plywood over it . Can I use a premium underlayment or felt and underlayment? Cork? Thanks so much!
Reply by HoskingHardwood : Since you are floating the floor and not "adhering or nailing down" the new to the old. you should be fine to run the new flooring in the same direction as the old as long as the old floor is flat. 1/4 cork can be used as an underlayment and is a firmer type of underlayment than the foam or pad type. Cork will reduce sound transmission also. 
By:
Date: February 1, 2019
Page Rating: (5.0/5)
Comments:
Wonderful article. Thank you. Wondering if you need to have an underlayment for floating non engineered hardwood on a second Story with plywood subfloor?
Reply by HoskingHardwood : If the flooring is going to be stapled/nailed down then we would recommend using a 15 lb black felt or kraft paper under the flooring as to help retard any moisture migration up through the subfloor. 
By:
Date: January 13, 2019
Page Rating: (4.5/5)
Comments:
I wish I saw this article sooner. i recently installed wood floor in my house, one of my main concern is soundproofing. I was told by the installer that with cork underlayment, you cannot do nail down, it must be glued down. Glad to be proven orherwise. Would using 12mm cork underlayment add more soundproofing? Also, how would one tack down the cork underlayment on the plywood subfloor, do we nail it then?
Reply by HoskingHardwood :

We install 6 mil. (1/4 inch thick) all the time under hardwood. 1-3/4 to 2 inch nails/staples will still grip the subfloor.  I would not advise using any thicker cork underlayment unless you are using a "Floating Floor"  which doesn't get nailed down. You can view all of our articles on the site map. 

By:
Date: January 8, 2019
Page Rating: (4.5/5)
Comments:
I am looking for underlay for 1st floor of by double storey house.i am doing the flooring with pre finished engineered spotted gum flooring,I need a good underlay to prevent the noise,can someone recommend which underlay suits to avoid the noise at 1st floor.Thanks.
By:
Date: October 24, 2018
Page Rating: (5.0/5)
Comments:
Great article. Thanks for the info. I want to use a cork or rubber underlayment under a solid or engineered hardwood floor. Everyone is telling me to nail, not glue, but my primary concern is sound control as Im in an old wood framed multi-unit building and noise is a big issue. What is best for minimizing sound transfer if I dont want to go with the floating option? (Im trying to avoid those annoying transition "bumps" between rooms)
Reply by HoskingHardwood : 1/4 inch cork using 2 inch staples or cleat nails. For thinner engineered flooring thinner gauge and 1-3/4 nails or staples depending on what that particular manufacturer states. 
By:
Date: October 24, 2018
Page Rating: (5.0/5)
Comments:
very well presented
By:
Date: October 16, 2018
Page Rating: (4.0/5)
Comments:
Good information but would prefer some brand names so it makes easy to buy. Thanks
By:
Date: September 19, 2018
Page Rating: (5.0/5)
Comments:
Very useful information and easy to understand. I noticed some people complaining that not enough info was given about special or very old slat subflooring or no technical specifications. This article gives good and complete info for what to use and why. It is not an installation manual for rebuilding or repairing an old subfloor nor a white paper with complete data for various underpayments. Its a good basic article. Thank you.

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