Downsides of Vinyl Plank Flooring: What Your Flooring Store Should Tell You

You just picked out beautiful vinyl plank flooring. Then you started reading about mold growing underneath it. Now you're not sure what to do.

Here's the good news. Mold under vinyl plank flooring is preventable. But it takes the right prep work before a single plank goes down.

As a local flooring store in Spokane, we help homeowners make smart flooring choices every day at our showroom on East Broadway. In this guide, we break down why mold forms under vinyl plank flooring and how to stop it. We'll cover the common causes, simple prevention steps, and what to ask your installer before work begins.

Can Mold Really Grow Under Vinyl Plank Flooring?

Yes, mold can grow under vinyl plank flooring if moisture gets trapped beneath it. But that doesn't mean vinyl is a bad choice. It means the installation prep matters more than most people think. Vinyl is waterproof on the surface. But it does not let air pass through. Any moisture underneath has nowhere to go.

Common causes include:

• Damp or unsealed concrete subfloors
• No moisture barrier installed
• Water leaks or flooding that seep under the edges
• High indoor humidity without proper airflow

The best way to prevent mold is to test subfloor moisture levels before installation. Use a quality moisture barrier. And work with an experienced flooring store that follows proper prep steps.

Mold needs three things to grow: moisture, warmth, and a food source. Dust, adhesive residue, and paper-backed underlayment can all feed mold under your floor. Add trapped moisture and a warm room, and mold can start forming fast.

According to FEMA, mold can begin growing on damp surfaces in as little as 24 to 48 hours. That's why what happens before your vinyl goes down is so important.

In our Spokane showroom on East Broadway, one of the most common questions we hear is, "Is vinyl plank safe from mold?" The answer is always the same. The vinyl itself resists mold just fine. The problem starts when moisture sits beneath it with no way to dry out.

The good news? Every cause of mold under vinyl flooring has a fix. And most of those fixes happen during installation — not after.

What Causes Mold Under Vinyl Flooring?

Most mold problems under vinyl plank flooring start before the floor is even installed. Knowing the causes helps you avoid them.

Damp or unsealed concrete subfloors are the most common problem. Concrete holds moisture. If it wasn't dried or sealed properly, that moisture moves upward and gets trapped under the vinyl.

A missing or damaged vapor barrier leaves your floor exposed. Without this layer, there is nothing to block moisture from reaching the underside of your planks.

Installing over water-damaged material is another common mistake. Old underlayment, plywood, or existing flooring that has water damage can carry mold spores and moisture into your new floor.

Leaks after installation cause trouble too. A pipe leak, appliance leak, or even a small flood can send water under the edges of your vinyl. Once it's underneath, it stays there.

High-humidity rooms without enough airflow create the perfect setting. Bathrooms, basements, and laundry rooms in Spokane homes are the areas we see this most often.

• Damp concrete subfloor — Test moisture levels and seal before installation
• Missing vapor barrier — Install a quality moisture barrier over concrete
• Water-damaged existing flooring — Remove and replace damaged material first
• Post-install leaks — Fix leaks quickly and inspect under edges
• High humidity, poor airflow — Add ventilation or a dehumidifier to the room

How to Prevent Mold Under Vinyl Plank Flooring

Preventing mold under vinyl plank flooring comes down to controlling moisture before and during installation. These steps are straightforward when you know what to do.

1. Test your subfloor moisture levels. Before any flooring goes down, run a moisture test. The industry standards are the calcium chloride test (ASTM F1869) and the relative humidity test (ASTM F2170). These tell you if your concrete slab is dry enough for vinyl plank.
   
2. Install a vapor barrier on concrete subfloors. A proper moisture barrier blocks water vapor from rising through the concrete. This single step prevents most mold issues we see in Spokane homes.
   
3. Use mold-resistant underlayment. Not all underlayment is the same. Choose one that resists moisture and mold growth. Avoid paper-backed options on concrete.
   
4. Keep indoor humidity between 30% and 50%. The EPA recommends this range to slow mold growth. In rooms like basements, bathrooms, and laundry areas, a dehumidifier or exhaust fan helps keep levels in check.
   
5. Make sure the room has good airflow. Stagnant air holds moisture. Open vents, use fans, or check that your HVAC system reaches the room where your new floor is going.
   
6. Hire a professional installer. A trained installer knows how to prep your subfloor the right way. They catch problems that are easy to miss on your own.
   

Our installers always run a moisture test before starting any vinyl plank job. If the numbers are too high, we pause the project and walk you through next steps. No guesswork.

Why Professional Installation from a Flooring Store Matters

DIY vinyl plank installation looks simple in online videos. But most mold problems we see in Spokane homes come from skipped prep steps during self-installs.

Moisture testing, subfloor leveling, and vapor barrier placement take time and the right tools. These steps are easy to skip when you're doing it yourself. But they're the exact steps that prevent mold from forming later.

A professional installer familiar with Spokane's climate knows what to watch for. Our area gets cold, damp winters. Concrete slabs in older homes along East Sprague or in the Valley often hold more moisture than homeowners expect. Local experience matters when deciding how to prep your subfloor.

Buying from a local flooring store also gives you access to in-person advice. You can bring in photos of your space, ask questions about your specific subfloor, and get product recommendations that match your room's conditions. That's harder to get from an online retailer.

We recently worked with a homeowner who had mold under vinyl plank that was installed without a moisture barrier. The previous install was a DIY project. We removed the flooring, treated the subfloor, installed a proper vapor barrier, and laid new vinyl plank the right way. The issue hasn't come back.

When you work with a reputable flooring store, your installation often comes with a warranty that covers prep-related issues. That gives you peace of mind that a box of planks from a warehouse can't offer.

Best Vinyl Plank Flooring Options for Moisture-Prone Areas

Not all vinyl plank flooring handles moisture the same way. The core material inside each plank makes a big difference.

SPC (stone polymer composite) has a rigid, dense core made with limestone. It holds up well against moisture and temperature changes. SPC is a strong pick for basements and bathrooms in Spokane homes where dampness is more common.

WPC (wood polymer composite) has a softer, slightly thicker core. It feels warmer underfoot and absorbs more sound. WPC works well in kitchens, living rooms, and bedrooms where comfort matters most.

Both options are 100% waterproof on the surface. The difference is how they perform over time in rooms with higher moisture exposure.

When comparing products, here's what to look for:

• Waterproof core — Make sure the product says SPC or WPC, not just "water-resistant."
• Built-in underlayment vs. separate — Built-in pads save a step, but a separate mold-resistant underlayment often gives better moisture protection on concrete.
• Thickness of 5mm or more — Thicker planks feel more stable and hold up better in high-traffic areas.
• Wear layer of 12 mil or higher for residential use — This helps protect the surface from scratches and scuffs over the life of your floor.

Try Our Flooring Visualizer Before You Buy

Our flooring visualizer takes out the guesswork. You can see your space changed right away.

Upload a photo of your room. Pick a product from our collection. Watch what happens instantly. The realistic picture shows you exactly how different floors will look in your actual space.

Step 1: Upload your photo. | Step 2: Pick a product. | Step 3: See the change right away!

Use the visualizer to pick your favorites online. Then ask for those specific samples to test in person. This gives you both online ease and hands-on proof.

Try the Pro Floors and Blinds Flooring Visualizer today!

Every home is different. A vinyl plank that works great in an upstairs bedroom may not be the best fit for a below-grade basement. That's why it's worth asking your flooring store which products perform best for your specific space and conditions.

At Profloors & Blinds, We'll help you find the right floor and handle the installation from start to finish. Call us at (509) 866-6776 to schedule a consultation.