Coretec Flooring Thickness: How to Choose Between 4mm, 5mm, 6mm, 7mm, and 8mm

I've been a quality compliance manager in the building materials industry for over 5 years now. Every quarter, I review roughly 200 unique flooring orders before they go out to our dealers and contractors. And if there's one question I get asked more than any other, it's this: "What Coretec thickness should I use?"

The short answer? There's no single right answer. It depends on your subfloor, your traffic expectations, whether you're installing herringbone, and—let's be honest—your budget. What worked for a commercial lobby in Chicago won't work for a second-floor bedroom in a Phoenix condo. Here's how I break it down.

Before We Start: The Two Core Technologies

First, a quick distinction. Coretec uses two main rigid core technologies: WPC (Wood Plastic Composite) and SPC (Stone Plastic Composite). Both are "rigid core," but they're not the same.

• WPC (Wood Plastic Composite): Softer, warmer underfoot, slightly thicker. Coretec's WPC is typically found in thicker planks (6mm+, often with attached underlayment). It's the original rigid core technology and has been around since 2012.
• SPC (Stone Plastic Composite): Denser, stiffer, more impact-resistant. Coretec's SPC is often used in their thinner, higher-density products (4mm-6mm core). It's less forgiving on subfloor imperfections but more dimensionally stable in extreme temperatures.

Which is better? Depends. WPC is more comfortable. SPC is more stable. I've seen contractors argue for both. Let's get into the specifics.

Scenario 1: You Have a Flat, Stable Subfloor (Concrete or Wood)

If your subfloor is flat (within 3/16" over 10 feet), clean, and dry, you have the most flexibility. Honestly, a 4mm or 5mm SPC product like Coretec's Pro Plus or Enhanced lines will work fine.

My recommendation: 5mm total thickness (4mm core + 0.5mm wear layer + 0.5mm backing). This is the sweet spot for residential applications.

Why? The thinner profile costs less per square foot. It transitions easier to existing tile or hardwood. It's lighter to carry up stairs. And on a flat subfloor, you don't need the extra thickness to hide imperfections.

What I've learned the hard way: Everything I'd read said thicker boards are always better. In practice, for a straightforward residential install on a clean slab, a 4mm or 5mm product is not only sufficient—it's easier to install and makes for cleaner transitions.

Scenario 2: Your Subfloor Has Minor Imperfections (Old Wood, Slightly Uneven Concrete)

This is the most common scenario, especially in renovations. The subfloor isn't terrible, but it's not perfectly flat either. You've got some dips, some high spots, or an old hardwood floor underneath that's mostly level but has a few low areas. This is where the extra thickness of a WPC product really shines.

My recommendation: 6mm to 7mm total thickness. Coretec's One Plus (6.5mm) or Studio (7mm) lines are ideal here. They have a thicker WPC core that can bridge small gaps (up to 1/8" in my experience) without telegraphing the imperfections to the surface.

Why not SPC here? SPC is stiffer. It doesn't "give" as much. If your subfloor has a 1/8" dip, a thin SPC plank will often crack at the click-lock joint over time. The WPC core compresses slightly, absorbing the irregularity.

A reality check: I only believed this after ignoring it once. In 2022, we specified a 5mm SPC for a project over an old, slightly uneven plywood subfloor. The contractor pushed back, saying we needed a thicker WPC. I didn't listen. Six months later, we had 8 separate click-joint failures in a 2,000 sq ft install. The redo cost us $3,200. Now every contract includes a minimum thickness based on subfloor condition.

Scenario 3: You're Installing a Herringbone Pattern

There's a common belief you can install any LVP in a herringbone pattern. That's wrong. And honestly, I've seen some beautiful installations ruined by choosing the wrong product.

Herringbone requires short, equal-length pieces (usually a 2:1 or 3:1 ratio). The locking mechanism needs to be extremely strong to handle the angular forces. And the board needs to be thick enough to resist the stress points at the intersections.

My recommendation: 7mm or 8mm total thickness, SPC core. Coretec's Stone line (7mm) or Grande line (8mm) specifically support herringbone installations. The thicker SPC core provides the rigidity needed for the pattern to look right and stay locked.

Why thicker for herringbone? In a standard staggered layout, the click-lock joints aren't under as much stress. In herringbone, each plank is locking into multiple neighbors at odd angles. A thin board (4-5mm) will flex and loosen over time. The thicker board gives more surface area for the locking mechanism to engage.

Don't take my word for it: Coretec's own installation guidelines recommend minimum 7mm thickness for herringbone patterns. As I tell our dealers: ignore this and you're creating a call-back in 18 months. It's not if—it's when.

Scenario 4: Commercial or High-Traffic Residential

If you're flooring a retail space, a busy hallway, or a home with dogs, kids, and a lot of foot traffic, you need to think beyond core thickness to wear layer thickness. The wear layer is the clear top coat. It's measured in mils (thousandths of an inch). Coretec typically offers 12 mil, 20 mil, and 30 mil wear layers.

My recommendation for high-traffic areas: At least 7mm total thickness and a 20 mil wear layer. The thickness provides impact resistance. The wear layer provides scratch and scuff resistance. They work together.

What I've seen in the field: The conventional wisdom is that a thicker wear layer always justifies a higher price. My experience with 50+ commercial installations suggests otherwise. If the core is too thin (under 6mm), even a 20 mil wear layer won't save the installation from subfloor imperfections. The planks will eventually crack or separate. The wear layer is a coating; the core is the structure. Both matter.

How to Know Which Scenario You're In

Here's a quick decision guide I use when I'm walking a jobsite:

1. Check your subfloor flatness first. Use a 10-foot straightedge. If you see gaps larger than 3/16", level it or choose a thicker product (7mm+). If it's flat, you can consider thinner products.
2. Check your subfloor type. Concrete? SPC is fine. Wood subfloor? WPC or a thicker SPC (6mm+).
3. What's your pattern? Herringbone? Minimum 7mm, SPC core. Staggered? You have more options.
4. What's your traffic level? Residential with reasonable use? 5-6mm is sufficient. Commercial, heavy traffic, dogs with long nails? 7mm+ with a 20 mil or 30 mil wear layer.
5. What about transitions? If you're matching existing 1/2" hardwood or 3/8" tile, a thicker product (7-8mm) may create a trip hazard without a reducer. Factor that into your choice.

The fundamentals haven't changed: a flat subfloor and proper installation matter more than thickness alone. But the execution has transformed. We have more options now than we did in 2018, when 4.5mm was the standard. As of 2025, any Coretec product between 5mm and 8mm can be a good choice—for the right project. The trick is knowing which project you have.

And if you're still unsure? Pick the 7mm. It's the Goldilocks zone. It works on most subfloors, supports most patterns, and gives you margin for error. I've never received a call-back on a 7mm installation that wasn't caused by a flooding or a missed subfloor issue. That's about as close to a guarantee as I'm willing to give.