Some laminate flooring is now available with the underlayment attached. This reduces the waste and bulk that would come from a separate underlayment roll/sheet purchase. It makes the product more installer-friendly.

Underlayment helps “cover up” subfloor irregularities, such as irremovable adhesive from the subfloor. Larger flaws may require patching and filling, however. Keep in mind that underlayment does not solve every irregularity.

Just like with the installation of the laminate itself, underlayment and/or vapor barrier should be “floated.” With humidity and temperature changes, the flooring will expand and contract as one unit.

TYPES OF UNDERLAYMENT:

VAPOR BARRIER: durable plastic – usually polyethylene – with a thickness of .2 mm, applied with an overlap of 8” or more; helps in areas where moisture may be a problem

UNDERLAYMENT FOAM: 2-3 mm thick roll of closed-cell plastic that acts as a sound reducer, cushioning, and squeak-reducer

VAPOR AND FOAM: combination of vapor barrier and underlayment foam; is convenient when installing over concrete subfloors and crawl spaces -- also known as 2-IN-1 FOAM

CORK AND RUBBER: pieces or rolls that provide exceptional sound reduction and increased comfort; most expensive type of underlayment

Both a vapor barrier AND underlayment should be used when dealing with subfloors that are concrete – even if they have surface flooring installed over it. Crawl spaces are often problematic areas for moisture and should use both as well. Failure to use a vapor barrier can cause a laminate floor to bow.