Wine Glasses Are Ruining Your Flooring. Here's Why Your Coretec Needs a Better Transition.

I have a controversial take for a quality inspector: that wine glass you dropped? It's not the problem. The real issue is the transition you didn't think about between your Coretec and the adjacent room.

Let me explain. I review flooring installations for a living—roughly 200 unique installs annually over the last 4 years. In my Q1 2024 audit of 14 Coretec jobs, I found that 12 of them had acceptable clicking and locking on the planks themselves. But only 3 had transitions that would survive a spilled glass of red wine without catastrophe.

Here's the thing people don't realize: Coretec Pro Plus is engineered to handle spills. The transitions between rooms aren't.

The Transition Trap

It's tempting to think that if you buy high-end vinyl like Coretec, the whole job is bulletproof. But the weak link in most floating floor installations isn't the product—it's where the product stops. Where your Coretec meets carpet, tile, or hardwood, you need a transition strip. And I've seen more water damage from the underside of a bad transition than from a direct spill on the plank itself.

What most people don't realize is that many standard T-molding transitions aren't sealed underneath. When that wine glass tips over—and it will—the liquid doesn't just sit on top. It wicks through the tiny gap between the transition and the plank edge. Once it's under the floor, it has nowhere to go but sideways. That's what causes the subfloor damage that makes your floor feel spongy 6 months later.

Honestly, I'm not sure why transition manufacturers haven't standardized a simple gasket system. My best guess is that it adds cost and complexity to an item most people don't think about. But I've never fully understood the logic of spending $6 per square foot on flooring and $0.60 on a transition that can ruin it.

What Coretec Pro Plus Installation Instructions Actually Say

Let me save you some reading. The Coretec Pro Plus installation guidelines do mention transitions. They say you need expansion gaps (which is standard). They mention that transitions should be used at doorways. But here's what they don't spell out: The moisture barrier underneath your Coretec needs to be continuous through the transition.

In the installs I've reviewed, the most common failure mode is this:

• Coretec planks clicked in perfectly over the underlayment
• Transition at the doorway was a simple aluminum T-strip, nailed into the subfloor
• The underlayment was cut at the doorway, exposing the subfloor directly to the transition gap
• Result: any spill near the door went straight to the subfloor

I ran a blind test with our installation team last year: same Coretec floor with two different transition treatments. One used a standard T-strip over cut underlayment. The other used a continuous underlayment with a purpose-sealed transition cover. We poured 8 ounces of water near each transition. The first one wicked moisture 14 inches under the floor in 30 seconds. The second held it at the surface. The cost difference? About $35 per doorway.

The "Wine Glass" Test You Haven't Heard Of

Here's something vendors won't tell you: there's no industry standard for testing transitions against liquid ingress. There is a test for the plank itself (Coretec passes it easily), but the transition? It's a no-man's-land. That's why I always tell clients to ask their installer one question: "How is the transition sealed against liquid?"

If they look confused, you have your answer.

Part of me feels bad for the installers. They're following the product instructions, which say "install transitions per manufacturer guidelines." But the guidelines assume a level of understanding most homeowners don't have. It's tempting to think that a floating floor is a floating floor—click, lock, done. But the transition is where your floor stops floating and starts failing.

The Fix Is Painfully Simple

For the $18,000 jobs I've consulted on, specifying moisture-proof transitions added less than $200 total. That's 1.1% of the project cost for what is arguably the most critical vulnerability.

Here's what you need to know:

• Don't cut the underlayment at the doorway. Run it continuous, even if it means a small hump under the transition cover.
• Use vinyl-to-vinyl transitions when possible. Some manufacturers make sealed versions. They cost more. Buy them anyway.
• Silicone or caulk the underside of the transition track. A tiny bead of sealant where the track meets the subfloor keeps liquid from wicking sideways.

I get the pushback: "But the transition needs to allow for expansion!" Yes, it does. But expansion and moisture ingress are two different problems. A properly designed transition can handle expansion vertically (the plank moves under it) while sealing horizontally (liquid stays above the subfloor). The two aren't mutually exclusive.

Look, I'm not saying Coretec is bad. I review their product regularly and it's consistently among the best in class for dimensional stability and wear layer durability. But the best floor in the world is only as good as its worst transition. And right now, most transitions are the weak link.

When I implemented our verification protocol in 2022, I started rejecting installations where the underlayment was cleanly cut at doorways without a sealed transition system. The pushback from installers was immediate. "We've always done it this way." My response: "Then you've always had a vulnerability you didn't know about."

I'd rather spend 10 minutes explaining this up front than deal with the call 18 months later about the spongy spot near the kitchen doorway. An informed client asks better questions—and their floor stays dry.