Laminate flooring manufacturers will always recommend that you install underlayment before laying laminate flooring. Yet is it necessary? While underlayment is the safe, default choice, in some instances it is not necessary.
Begin with the manufacturers' recommendations and reasoning before moving onto the opposite view.
Reasons for Underlayment
- Sound: Laminate flooring is so thin that it needs underlayment's extra help to feel and act like real wood. Consider sound transmission. You do not need foam padding under solid hardwood for many reasons, and one reason is because hardwood alone limits the transmission of sound, both within the room and to floors below. Laminate flooring is thin--usually no more than 12mm--and is made of a type of fiberboard. So underlayment boosts laminate's sound absorbing qualities.
- Subfloor Imperfections: This is the biggest issue of all, what the flooring manufacturer might call "subfloor imperfections." This means that your subfloor is not perfectly flat and featureless, which describes many subfloors. Solid or engineered wood can bridge small gaps. Ceramic and porcelain tile can bridge those gaps, plus mortar works to fill them in. Underlayment helps to prevent laminate damage.
- Moisture: You will need moisture-proof underlayment when there is a chance of moisture migrating upward: concrete slab, tile, cement board, and even wood sub-floor or flooring over a crawlspace or other non-climate-controlled space. Underlayment and vapor barrier are not the same thing. Common foam underlayment will inhibit moisture. But there are types of underlayment that require a separate 6 mil. polypropylene vapor barrier.
- On Concrete: When you are installing on top of concrete, you may want the extra padding that underlayment provides to make it softer to walk on. Take note that underlayment is not considered a vapor barrier. Manufacturers typically recommend that you add a vapor barrier in addition to the underlayment.
- Margin of Safety For The Company: Product liability; providing a wide margin of safety; and appealing to a majority of installations: these are some reasons why flooring manufacturers make this blanket recommendation. It is a case of laminate makers wanting to ensure few problems with the greatest number of installations.
When You Do Not Need It At All
The only instance when you absolutely do not need underlayment is when it already has underlayment. Confused?
Your laminate might already have pre-attached underlayment, rendering separate underlayment unnecessary.
Rare only a few years ago, laminate with pre-attached padding is now found in great numbers. Over half of Lumber Liquidators' laminates come with pre-attached padding; over 75% of Pergo's laminates now have pre-attached underlayment.
In this case, not only is separate underlayment unnecessary, it is detrimental to the stability of your flooring. When you have pre-attached underlayment, manufacturers recommend that you still install vapor barrier.
When You May Not Want It
Generally, you want to use underlayment. But if you wish to squeeze by without using it, here are a few contrarian views on the matter:
1. When Cost Is an Issue
Underlayment can be surprisingly expensive. One premium underlayment, Roberts AirGuard, costs $0.55 per square foot. This is not expensive in relation to $7+ per square foot laminate. But when compared to cheap $0.49/sq. ft. clearance laminate, the underlayment costs more than the flooring itself.
2. When Your Base Surface is Moisture-Proof
One popular mode of installation is to put laminate on top of vinyl flooring. This eliminates the need for removing the vinyl floor. Vinyl flooring is not--or, should not--be water-permeable. If it is water-permeable, somebody installed the floor wrong.
Even hastily-installed peel 'n' stick vinyl floor tiles can do a reasonably good job of holding back the moisture.
3. When You Do Not Want a Hollow Feeling Under Foot
Foam laminate underlayment softens your footfall. But it also makes the flooring feel hollow.
You notice it immediately when you walk from a solid surface, like tile, to laminate with underlayment. It is a singular feeling that alerts you to the fact that you are on laminate with foam padding.
Laminate flooring with denser felt underlayment more closely approximates the feeling of real wood flooring.
4. When You Have Just Installed Subfloor
Ripped-up flooring causes subfloor problems. Tile leaves behind chunks of mortar. Vinyl leaves adhesive. It's a big mess, and one that welcomes the assistance of underlyment's smoothing, bridging properties.
But when your subfloor is new and flat, and featureless--with no protruding screws or nails--it should not need the assistance of underlayment to make your laminate flooring lay perfectly.
Freshly installed OSB or grade-A plywood provide a smooth, perfect surface for laminate flooring installation.
Underlayment should be the default choice for most laminate floor installations. The only absolute exception is when your laminate has pre-attached underlayment. You can leave out the underlayment if you can accept a few conditions--heavier foot fall, increased sound, and possible moisture migration.