What Do You Need to Put Under Laminate Flooring? Essential Underlayment Tips

Installing laminate flooring is an exciting home improvement project, but the success of the entire system hinges on what you place beneath the planks. The underlayment is not just a optional extra; it is the foundational layer that provides stability, sound absorption, and moisture protection. Skipping this step or choosing the wrong materials can lead to squeaks, warping, and premature failure of your beautiful new floor.

The Critical Role of the Underlayment

Under laminate flooring, the underlayment serves several vital functions that the hard surface alone cannot provide. It acts as a moisture barrier, preventing rising damp from seeping up into the planks and causing mold or structural damage. It also provides a level surface to correct minor imperfections in the subfloor, which is essential for the longevity of the laminate. Without this cushioning layer, every tiny crack or nail head in the subfloor would translate directly to the surface of your finished floor, creating an uneven and uncomfortable walking experience.

Standard Underlayment Requirements

Most laminate flooring manufacturers require a specific thickness of underlayment to ensure proper expansion gaps and structural integrity. A typical specification is a thin, foam-based underlayment that is 2mm to 6mm thick. This layer must be firm enough to support the weight of the flooring yet thin enough to allow the manufacturer’s recommended expansion gap to be maintained around the perimeter of the room. Always refer to the specific instructions provided by your laminate brand, as requirements can vary significantly between products.

• Moisture Barrier: A critical feature, usually made of polyethylene, that prevents ground moisture from wicking up into the laminate.
• Cushioning: Provides a soft, comfortable feel underfoot and helps absorb minor impacts.
• Sound Dampening: Reduces footfall noise and helps insulate against sound traveling between floors.
• Subfloor Correction: Levels out minor bumps and irregularities to create a smooth surface for installation.

Assessing Your Subfloor

The type of subfloor you have dictates the underlayment strategy you must employ. A concrete slab foundation, common in basements and ground-level rooms, requires a robust moisture management system. You will need a thicker vapor barrier, and in some cases, a specialized moisture-proof underlayment, to prevent vapor transmission. Over wooden joists, the focus shifts to providing a stable, level base and absorbing sound, where a thinner foam underlayment is usually sufficient.

Additional Considerations for a Flawless Finish

Beyond the underlayment itself, there are other materials you need to prepare the perimeter of the room. Transition strips are necessary where the laminate meets other floor coverings like tile or carpet, providing a clean and safe edge. Furthermore, you should never rely on the underlayment to handle vertical transitions; door jambs will need to be trimmed to allow the flooring to slide underneath securely.

When rolling out the underlayment, pay attention to the seams. They should be laid in a staggered pattern, similar to brickwork, and securely taped to prevent them from separating during installation. This prevents gaps that could allow moisture to penetrate or create a weak spot that tears under the weight of the furniture.

Common Mistakes to Avoid

One of the most frequent errors DIYers make is using carpet padding or thick memory foam where laminate requires a firm surface. Excessive softness under laminate causes the locking mechanism to fail and creates an uneven surface that wears down the edges of the planks prematurely. Another mistake is taping the seams in the same direction as the plank installation, which can cause the tape to peel apart; remember to lay the rolls perpendicular to the floor’s length to maintain integrity.

Finally, ensure that the underlayment does not overlap the center of the room. It should run only to the wall, allowing the laminate room to expand and contract naturally. By investing time in selecting and installing the correct underlayment, you create a stable, quiet, and durable base that allows your laminate flooring to perform at its best for years to come.