Luxury vinyl tile (LVT) has become one of the most popular flooring choices for homes and businesses — it’s durable, beautiful, and easy to install.
But before laying those planks, one question often comes up:

Do I need a vapor barrier between the subfloor and my LVT?

The answer depends on your subfloor material, installation type, and the moisture level of your space. Let’s break down when a vapor barrier is necessary, when it’s optional, and when it might actually cause more harm than good.

🧱 What a Vapor Barrier Does

A vapor barrier (also called a moisture barrier) is a thin layer — usually plastic or polyethylene — that prevents moisture vapor from rising through the subfloor and damaging the flooring above.

If excess moisture gets trapped under your LVT, it can cause:

• Bubbling or lifting of planks

• Mold or mildew beneath the floor

• Adhesive failure (for glue-down installs)

• Foul odors or discoloration

🏠 Subfloor Type Matters Most

1. Concrete Subfloors

If you’re installing LVT directly over concrete, a vapor barrier is almost always recommended — even if the concrete looks dry.
Concrete naturally emits small amounts of moisture, and over time, that moisture can migrate upward and compromise your flooring.

Recommendation:

• Use a 6-mil (minimum) polyethylene vapor barrier under the LVT if you’re in a basement, on-grade, or slab-on-grade area.

• For glue-down LVT, follow the adhesive manufacturer’s moisture limits and test the slab first.

2. Wood Subfloors

Wood is more breathable than concrete and can tolerate some vapor transmission. In most cases, you don’t need a vapor barrier over wood subfloors — especially in above-grade areas where humidity is controlled.

However:
If the room is prone to moisture (bathrooms, laundry rooms, or kitchens), you may use a moisture-resistant underlayment designed for LVT rather than a full plastic barrier.
This allows the floor to “breathe” while still protecting against small spills or condensation.

3. Existing Vinyl or Tile Flooring

If you’re installing LVT over an existing hard surface that already blocks moisture (like vinyl sheet or ceramic tile), adding another vapor barrier can trap moisture between layers, causing it to condense under the flooring.

In this case: Skip the vapor barrier entirely and make sure the existing floor is clean, dry, and well-adhered.

🧰 Floating vs. Glue-Down Installation

Quick Tip:
If your LVT comes with an attached pad or backing layer, double-check the manufacturer’s guide. Some built-in backings already include a moisture barrier, and adding another layer can void your warranty.

🧪 How to Test for Moisture in Concrete

Before deciding, it’s smart to measure how much vapor your concrete subfloor emits.
Two common tests:

1. Plastic Sheet Test:
   Tape a 2x2-foot plastic sheet to the floor and leave it for 48–72 hours. If condensation forms underneath, you’ll need a vapor barrier.

2. Calcium Chloride or RH Test:
   Professional tests measure the exact moisture vapor emission rate (MVER) or relative humidity inside the slab. Most LVT adhesives require MVER below 5 lbs / 1000 sq ft / 24 hr.

⚠️ When You Should Not Use a Vapor Barrier

More isn’t always better. A vapor barrier can cause problems if:

• You’re installing over a wood subfloor and block normal airflow.

• You’re layering over existing vinyl, linoleum, or tile floors that already resist moisture.

• You’re using an adhesive system that specifically says no plastic film beneath.

In these cases, a breathable LVT underlayment is the safer alternative.

🌡️ Managing Humidity the Right Way

Even the best vapor barrier won’t fix high ambient humidity.
Keep your interior relative humidity between 35%–65%, and ensure the subfloor is clean, level, and fully dry before installation.
Use a dehumidifier in basements or coastal regions to maintain stability — your LVT will thank you with fewer gaps or curls over time.

✅ Quick Reference: Do You Need a Vapor Barrier?

🏁 The Bottom Line

A vapor barrier under LVT is not one-size-fits-all.
It’s essential over concrete subfloors or moisture-prone areas, but often unnecessary — or even counterproductive — over dry, wood-based floors.

When in doubt, check the installation guide for your specific LVT product and evaluate your room’s conditions.

🛒 Find the Right LVT for Your Project

At Best Carpet Value, we carry a full range of Luxury Vinyl Tile (LVT) products engineered for performance, beauty, and ease of installation.

✔️ Waterproof options for basements and kitchens
✔️ Built-in underlayments for faster installs
✔️ Commercial-grade durability at warehouse pricing