Water under laminate or vinyl plank flooring

Why floating floors trap water

Laminate and click-together vinyl plank float on top of the subfloor, usually over a thin underlay. They are not glued or nailed down. Water that reaches the edge of the room, or seeps through the joints, spreads underneath by capillary action and has no way out. The surface can look perfect while there is a film of water below.

How to tell water is underneath

• Boards feel spongy, or squelch when stepped on
• Edges of laminate boards are raised or swollen
• Joints are opening, or the surface is bubbling
• Water squeezes up through joints under pressure
• A musty smell develops over the following days
• The baseboards are stained or swollen at the bottom

Lifting a transition strip or a board at the edge of the room shows what is happening under the floor.

Laminate

Laminate has a core made of wood fibre pressed with resin. It is durable on the surface and very vulnerable at the edges. Once the core takes in water:

• The edges swell and stay swollen
• The decorative layer can lift
• The boards will not click back together properly

Swollen laminate does not recover as it dries. Affected boards are replaced. “Water-resistant” laminate copes with spills wiped up promptly. It does not survive water sitting under it.

Vinyl plank

Luxury vinyl plank and tile are waterproof as products. Water does not damage the planks. The problem is what is underneath:

• A wooden subfloor that stays wet swells and grows mold
• Underlay holds moisture
• On concrete, trapped moisture breeds mold and odour

So the floor still has to come up in the affected area. The difference is that vinyl planks can often be cleaned, dried and reinstalled, if they come apart without damage to the locking edges.

What to do

1. Stop the source and extract any standing water.
2. Find out how far the water went. It is usually further than it looks.
3. Remove baseboards along the affected walls.
4. Lift the flooring back to dry subfloor, working from the nearest wall. Floating floors come up row by row.
5. Remove wet underlay.
6. Dry the subfloor with air movers and a dehumidifier until moisture readings are normal.
7. Check the base of the walls. Water under the floor has usually reached the drywall.
8. Reinstall or replace.

The matching problem

Laminate and vinyl products change and are discontinued. If the damaged area cannot be matched:

• Check for leftover boxes from the original installation
• Take boards from inside a closet to patch a visible area, and put the new ones in the closet
• Replace the floor to a natural break, such as a doorway
• Where the floor runs continuously through several rooms, the extent of replacement is something to raise with your adjuster

Over concrete and over wood

On a basement slab, the concrete itself must be dry before new flooring goes down. Concrete holds moisture for a long time, and a moisture test is worthwhile.

On a wooden subfloor, check for swelling at the panel edges and for staining. Swollen subfloor panels make a new floor uneven and may need replacing.

Glue-down and sheet vinyl

Glued vinyl and sheet vinyl do not let water spread as easily, but water that gets underneath at an edge or seam is sealed in. Bubbles, lifting seams and discolouration show where. The affected section is cut out and replaced.

Preventing it

• Wipe up spills promptly, especially along edges and near dishwashers and fridges
• Seal the perimeter in kitchens and bathrooms where the manufacturer allows
• Fit leak sensors under sinks and beside appliances
• Use a flooring rated for the room in basements and bathrooms

Why lifting it early matters

It is tempting to leave a floor that looks fine. The trouble is what happens underneath in the following days.

• Within a day or two, mold can begin on a damp wooden subfloor and on the paper face of drywall at the base of the walls
• Underlay made of foam or felt holds water against the subfloor like a sponge
• On concrete, moisture trapped under a vapour barrier has nowhere to go and turns musty
• Swelling in laminate becomes visible only after the damage is done

Lifting a few rows on the day of the leak is a small job. Dealing with a moldy subfloor a month later is not.

Kitchens, islands and cabinets

Floating floors are often installed up to the cabinets, but sometimes run underneath them or under a kitchen island. Water follows the floor. Where the floor continues under cabinets, drying may mean removing toe-kicks to get air underneath, and in some cases removing cabinets. Fridges with ice makers and dishwashers are the usual sources, and both hide the leak.

Can the same boards go back?

• Vinyl plank: often, if the locking edges are intact and the planks are cleaned and dried on both sides. Number the rows as they come up.
• Laminate: only boards that never got wet. Check the edges closely. Any swelling means the board will not sit flat.
• Underlay: replace it. It is inexpensive and hard to dry and clean properly.

Let new laminate sit in the room for the time the manufacturer specifies before it is laid, so that it adjusts to the temperature and humidity.

How to tell the subfloor is dry

By measurement, not by touch. A moisture meter reading on the affected subfloor is compared with a reading from a dry area of the same material elsewhere in the house. New flooring goes down when the two match. On concrete, a taped-down square of plastic left for a day or more is a simple check: condensation under it means the slab is still giving off moisture.

More: water damage restoration.