Laminate Underlayment: What to Know Before Installation

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 used to other types of floors like solid hardwood, vinyl, and tile, all of which require no underlayment, you might be surprised to learn that underlayment is practically required below laminate flooring.

What Is Laminate Underlayment?

Laminate underlayment is a soft pad that is installed under laminate flooring. The underlayment helps the laminate planks lay smoother, connect better, and for the flooring to feel slightly softer underfoot. Underlayment is either pre-attached to the bottom of the laminate flooring by the manufacturer or it is installed separately by the user.

Attached Underlayment

When the underlayment is attached to the flooring, nothing else needs to be done. The laminate flooring is ready for installation. Using a second layer of underlayment is useless and can even be detrimental.

Separate Underlayment

When the underlayment is not attached, rolls must be purchased and installed separately. Underlayment is made 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 typically ranging from 2 mm to 3 mm.

Why Laminate Flooring Needs Underlayment

Laminate flooring is thin and is constructed of a type of fiberboard rather than solid hardwood or even plywood, as with engineered wood flooring. Because laminate flooring can be difficult to install on surfaces that are even the least bit imperfect, underlayment is a recommended supplement.

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Corrects Minor Subfloor 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 this laminate damage.

Laminate underlayment cannot cure all imperfections, though. Filling in low spots with a fluid leveling compound that later hardens is one way to correct large depressions.

Large sheets of thin, smooth 1/4-inch luan ply are sometimes installed above the subfloor and below the soft laminate underlayment. While luan boards are often called underlayment, they are not the same as the soft, flexible underlayment required for laminate installation and are used in addition to the soft 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 an additional 6 mil. polypropylene vapor barrier. Flooring underlayment that includes a waterproof layer are also available.

One benefit of laying separate underlayment as opposed to installing laminate flooring with pre-attached underlayment is that separate underlayment provides a more cohesive barrier under the laminate. With pre-attached underlayment, the seams between the planks are gaps in the underlayment.

When Laminate Underlayment Is Not Necessary

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. A rare feature only a few years ago, laminate with pre-attached underlayment 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.

Not only is a second layer of underlayment unnecessary, but it can also be detrimental to the stability of your flooring. The planks will not properly lock together. If you do manage to lock the boards, they may eventually come unlocked because the base is not solid.

When Cost Is an Issue

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 the laminate flooring in an area that receives little attention such as a mudroom or laundry room, and you simply need to quickly install cheap flooring, laminate flooring can be installed without underlayment. The subfloor must be perfectly flat and featureless: no nails, screws, bumps, or dips. Keep in mind, however, that the floor's lifespan still may be reduced absent an underlayment.