Is LVP Waterproof in a Florida House on a Slab?

Is LVP waterproof? The plank is, if it has a rigid stone-polymer core, but the floor is not. Water that gets through the seams, around the edges or up from the concrete ends up under the planks, and a waterproof plank cannot stop that on its own.

That difference is the whole answer for a house on a slab in Sarasota or Bradenton. The label on the box describes what the plank does with a spill on top. What happens to your floor depends on the slab under it and on how the edges are finished, and those are install decisions, not product features.

Is LVP waterproof, or only the plank?

Luxury vinyl plank is a layered product. A rigid-core plank, the kind sold as SPC, has a mineral-filled stone-polymer core that does not absorb water. Leave a puddle on it overnight and the plank itself will not swell, soften or come apart the way a fibreboard core does. That is what "waterproof" on the carton means, and for an SPC plank it is a fair word.

A floor is a few hundred of those planks clicked together over an underlayment. The click joints are tight, and they keep an ordinary spill on top if it is wiped up. They are not a sealed membrane, and they were never meant to hold back water that stands on them, or water pushing up from underneath. Where the planks stop at a wall, a cabinet or a tub, there is a gap on purpose.

So the honest version of the label reads like this: the material is waterproof, the assembly is water-resistant, and the slab under it is a separate question. Some planks sold as water-resistant rather than waterproof have a core that does take on water. Read what the manufacturer's own terms say about standing water before you choose one, because they differ.

Where does water get under a vinyl plank floor?

Rarely from the middle of the room. It comes in where the floor ends, or where water sits for a long time:

• The edges. Every floating floor needs a gap at the walls so it can expand and contract, hidden under the baseboard. A spill that runs to the wall finds that gap.
• The sink, the dishwasher and the refrigerator. A slow drip from a supply line can run for a long time before anyone sees it, and it runs under the floor, not across it.
• The tub, the toilet and the laundry. Water that splashes over a tub edge or seeps around a toilet base lands right at the edge of the floor.
• The slider to the lanai. Wind-driven rain and wet feet come in at the same door, often in the same afternoon.
• The slab itself. Concrete passes moisture up from the ground as vapour all year, whether or not the surface looks dry.

What does a Florida slab add to the question?

Most houses here sit on a concrete slab on grade, and the slab sits on ground that is damp most of the year. A rigid-core vinyl plank does not mind that vapour the way a laminate board or a wood floor would. That is why waterproof vinyl and porcelain are the two floors most often reached for on a slab, and why LVP vs laminate comes down to what the core is made of.

What vinyl cannot do is make the moisture go anywhere. Under a floating floor it can collect against the underside of the planks and the pad. Under a glue-down vinyl floor it goes after the adhesive, and adhesives fail when the slab is still giving up moisture. Why floors fail in Florida houses explains the moisture test, which reads relative humidity inside the slab with probes rather than judging the surface by touch.

Many rigid-core planks come with a pad already attached. The manufacturer's installation instructions say whether a separate moisture barrier is still required over concrete, and what slab reading the plank is rated for. Those instructions, not the carton, decide how the floor goes down.

What happens when water gets under LVP?

The planks usually survive it. The trouble is everything else. Water trapped between a vinyl floor and a slab has nowhere to evaporate to, because the vinyl on top is the very thing keeping water out. It stays put, and in a warm, closed house that is how a floor starts to smell musty long before anything looks wrong.

On a floating floor, a known leak usually means lifting the planks from the nearest wall back to the wet area, drying the slab and the pad, and clicking the same planks back down if they are undamaged. A pad that has soaked through generally has to be replaced. On a glue-down floor, water that reaches the adhesive can release it, and the planks lift.

None of that is a reason to avoid vinyl. It is a reason to treat the slab and the edges as part of the floor rather than as something underneath it.

How is a vinyl floor installed so water stays on top?

Most of the work happens before the first plank goes down. On our flooring jobs the old floor comes out, the slab is tested, flattened and dry, and only then do the planks go in. A plank that bridges a dip flexes every time someone steps on it, and a joint that flexes is a joint that opens.

Then the edges. At the kitchen, the laundry and the sliders, the perimeter is detailed so a spill stays on top: the trim, the transition and, where the plank maker allows it, a flexible sealant at the tub, the shower curb and the toilet. The expansion gap still has to be there. The detail covers it rather than filling it with something rigid.

Sun matters too. Vinyl moves with temperature more than most floors, so a floor in front of a west-facing slider needs the expansion room its manufacturer specifies. A floor pinned at the edge by tight trim or a heavy island has nowhere to go, and a joint that is pushed open lets water in.

Is vinyl plank flood-proof?

No floating floor is. A plank can be waterproof and the floor can still be ruined by a flood, because floodwater gets under everything, and the pad, the trim and the walls around it do not share the plank's resistance. FEMA's list of flood-resistant materials does not name vinyl plank at all; it rates mortar-set porcelain and ceramic tile acceptable below the flood elevation.

If your floor sits below the flood line, or the house took water in a storm, start the conversation with tile rather than with the label on a vinyl carton.

Which rooms should get something other than LVP?

Bathrooms, laundries and shower floors get tile, installed over a waterproofing system. Those are rooms where water stands on the floor as a matter of routine, and no floating floor of any kind belongs there. Porcelain is effectively non-porous and bonded to the slab, so there is no layer underneath for water to collect in. A wood-look porcelain plank gives the look of a vinyl plank where the room is truly wet.

The kitchen, the hall to the sliders and the room off the lanai are where vinyl does its best work: water reaches them now and then, not as a matter of routine. Waterproof vinyl or tile both suit them, depending on whether you want the floor softer and quieter or harder and cooler underfoot. In a kitchen, the run under the dishwasher and along the toe-kick is the edge to plan.

A house that is shut up for the summer is a good case for rigid-core vinyl or tile, and a poor one for anything with a wood core. Nobody is there to see a leak when it starts.

What happens next

Start with the slab and the rooms, then choose the plank. The flooring bay in our Bradenton showroom holds wood-look vinyl planks on racks you can lift out, compare side by side and take home, next to the porcelain they are often weighed against.

Bring a plan or a photo of the rooms and we'll walk you through which ones want vinyl, which want tile and what the slab says. We sell it and we install it, and the crew is ours. Call (941) 253-0400, or send us your plans for a quote.