Why You Shouldn’t Install a Non-Permeable Vapor Barrier Between Your Subfloor and LVP Flooring

When installing luxury vinyl plank (LVP) flooring, ensuring proper moisture management is crucial. One common mistake homeowners and even some contractors make is placing a non-permeable vapor barrier between the subfloor and the new flooring. While the intention might be to prevent moisture issues, this can actually do more harm than good. Let’s discuss why a non-permeable vapor barrier can lead to mold growth, trapped moisture, and potential damage to your flooring investment.

Understanding Moisture Movement

Moisture naturally moves through different materials in a home, and the subfloor is no exception. Subfloors, especially those made of plywood or OSB (oriented strand board), can absorb moisture from various sources, including humidity in the air, leaks, or moisture wicking up from the ground in crawl spaces and basements.

If a non-permeable vapor barrier (such as plastic sheeting) is placed between the subfloor and LVP flooring, any moisture trapped beneath it has no way to escape. Over time, this leads to serious problems, including:

1. Mold and Mildew Growth

Mold thrives in moist, enclosed environments with organic materials to feed on. When moisture gets trapped beneath a non-permeable vapor barrier, it creates the perfect breeding ground for mold and mildew, which can spread quickly. Mold not only causes unpleasant odors but can also lead to health issues, especially for those with allergies or respiratory conditions.

2. Subfloor Deterioration

Wood subfloors need to breathe to maintain their integrity. If moisture cannot escape, the subfloor can become soft, warped, or even start rotting over time. This weakens the structural stability of the floor and can lead to costly repairs or full replacement.

3. Buckling and Lifting of LVP Flooring

LVP flooring is designed to be dimensionally stable, but when excessive moisture gets trapped underneath due to a non-permeable barrier, it can cause the planks to buckle, lift, or separate. This not only ruins the aesthetic of your floor but can also void manufacturer warranties.

What Should You Do Instead?

Instead of using a non-permeable vapor barrier, consider these alternatives:

• Use a Permeable Underlayment – Materials like felt or certain breathable underlayments allow moisture to escape while still providing cushioning and sound absorption.

• Ensure Proper Subfloor Preparation – Make sure the subfloor is dry before installation. A moisture meter can help determine if levels are safe for LVP installation.

• Improve Ventilation – If installing over a crawl space, ensure it has proper ventilation to reduce moisture buildup.

• Seal and Address Moisture Sources – If your subfloor has high moisture content, address the root cause first, such as fixing leaks or using a dehumidifier in damp areas.

Conclusion

While preventing moisture from seeping into your flooring is essential, using a non-permeable vapor barrier between the subfloor and LVP flooring is not the solution. Instead, focus on proper moisture management techniques to keep your floors in excellent condition for years to come. If you're unsure about the right approach for your specific installation, consulting with flooring professionals can help you make the best decision for your home.

For expert LVP installation and subfloor repair services, contact Plank Floor Pros today!

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