Laminate Underlayment: What to Know Before Installation

Installing Laminate Floor Underlayment

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With laminate flooring's many advantages, it can be an enticing floor covering choice for living rooms, bedrooms, home offices, and other low-moisture areas of your home. But if you are accustomed to other types of floors like hardwood, engineered wood, vinyl, and tile, all of which require no underlayment, you might be surprised to learn that underlayment is practically a requirement with laminate flooring.

What is laminate underlayment, why is it so necessary, and what type of underlayment should you purchase?

What Is Laminate Underlayment?

Laminate underlayment is a supplementary pad that is installed under laminate flooring to help the laminate planks lay smoother, connect better, and feel slightly softer underfoot. Underlayment is either attached to the bottom of the laminate flooring or it comes as a separate roll of polyethylene foam, felt, or cork.

The strips, usually 36 to 44 inches wide, are attached side-to-side with seaming tape or with attached adhesive strips. Rolls are from 30 to 100 feet long, with thicknesses ranging from 6 mm to 8mm.

One benefit of laying separate underlayment as opposed to installing laminate flooring with pre-attached underlayment is that separate underlayment provides a cohesive barrier under the laminate.

Why Laminate Flooring Needs Underlayment

Because laminate flooring is thin and is constructed of a type of fiberboard rather than solid hardwood or even plywood, as with engineered wood flooring, underlayment is a recommended supplement.

Corrects Minor Imperfections

Subfloors are often not perfectly flat and featureless. Subfloors exposed after the existing flooring has been removed are often dotted with nail holes, pits, gaps, grooves, and splinters. Even new subflooring can be considered less than perfect since the OSB or plywood sheets are seamed.

Solid hardwood or engineered wood can easily bridge small gaps, running directly over imperfections without the need for underlayment. Even ceramic and porcelain tile can bridge a few small holes and gaps, plus mortar works to fill them in. But laminate flooring will eventually telegraph (transmit or duplicate) subfloor imperfections. Underlayment helps to prevent laminate damage.

Laminate underlayment cannot cure all imperfections, though. Application of leveling compound is one way to fill in and correct large depressions. Thin, 1/8-inch luan ply is often used at an underlayment, too, residing above the subfloor and below the soft laminate underlayment.

Softens Footfall

When you are installing on top of hard surfaces such as concrete, you may want the extra padding that underlayment provides to make it softer to walk on. Wood subflooring has enough flexibility that underlayment will only slightly soften the surface of the laminate. But concrete, brick, and other forms of masonry practically demand the softening qualities that underlayment can provide.

While laminate underlayment softens your footfall, it can also make the flooring feel hollow. It is a feeling that is apparent when you walk from a solid surface, such as tile, to a laminate floor with underlayment. Laminate flooring with denser felt underlayment more closely approximates the feeling of real wood flooring.

Absorbs Sound

Laminate flooring is so thin that it needs underlayment's extra help to feel and act like real wood. Consider the issue of sound transmission. You do not need foam padding under solid hardwood for many reasons, but one reason is that hardwood is so dense that it limits the transmission of sound, both within the room and to floors below. 

Laminate flooring has neither thickness nor density since it is usually no more than 12mm thick and it is made of a type of low-density fiberboard. As a result, the underlayment will help boost laminate's sound-absorbing qualities, but only minimally so.

Controls Moisture

You will need moisture-proof underlayment or vapor barrier when there is a chance of moisture migrating upward from a concrete slab, tile, or cement board. Even a wood subfloor or flooring over a crawlspace or other non-climate-controlled space can be subject to rising moisture. Common foam underlayment will inhibit moisture, but there are types of underlayment that require a separate 6 mil. polypropylene vapor barrier.

Laminate Underlayment Pros and Cons

Pros

  • Softens footfall
  • Absorbs some sound
  • Helps planks lock together better
  • Assists in a flatter installation
  • Helps control some moisture

Cons

  • Extra cost (unless it is pre-attached)
  • Extra installation step
  • Hollow feeling and sound underfoot

When Laminate Underlayment Is Not Necessary

Generally, you will want to use underlayment under your laminate flooring. In one instance, though, underlayment should not be installed under any circumstances. In another instance, underlayment is an option.

When Underlayment Is Pre-Attached

The only instance when you absolutely do not need underlayment is when the laminate flooring already has underlayment attached to its bottom.

The laminate flooring that you intend to purchase might already have pre-attached underlayment, rendering separate underlayment unnecessary and even detrimental. A rare feature only a few years ago, laminate with pre-attached padding is now found in increasing numbers. Currently, over 50-percent of Lumber Liquidators' laminate floors come with pre-attached padding. Over 75-percent of Pergo's laminates now have pre-attached underlayment.

It is detrimental to the stability of your flooring to install underlayment beneath flooring that already has pre-attached underlayment. However, when you have pre-attached underlayment, manufacturers recommend that you still install a vapor barrier.

For a Bargain Installation

Laminate underlayment can be surprisingly expensive. Premium underlayments specially designed to mitigate sound can represent a large portion of your flooring bill. If you are installing in an area that receives little attention such as a mudroom or laundry room, and you simply need quick flooring, laminate flooring can be installed without underlayment. Floor performance will, in most cases, be affected.