Water Trapped Under Vinyl Plank on a Slab Floor

Waterproof planks, not a waterproof floor

Luxury vinyl plank and similar rigid-core flooring are now standard in many Aurora townhomes, newer apartment buildings and remodeled basements. The planks themselves shrug off spills, and that leads many owners to assume a leak cannot hurt them. The weak point is the joints. Water from a dishwasher, refrigerator line or toilet runs to the edge of the room and slips between planks or under the baseboard, onto whatever is beneath: an underlayment, a vapor barrier or bare concrete.

On a slab, that water has nowhere to drain and very little air to evaporate into. The planks act like a lid. Weeks later, someone notices a musty odor, a plank that moves when stepped on, or dark staining along the bottom of drywall. By then the slab and the base of the walls may have been damp for a long time.

Signs water is under the floor

Planks that click, flex or feel spongy where they used to feel solid
Edges that have lifted, peaked or separated at the seams
Water seeping up through seams when you press down on a plank
Swelling or staining at the bottom of baseboards or door casings
A musty smell in a room with no obvious wet surface
Moisture meter readings at the base of drywall near the suspected source

How it is usually handled

Stop and confirm the source.Appliance supply lines, toilet wax rings and a slow drain leak are the usual suspects. A plumber may be needed before any drying starts.
Map the wet area.A contractor uses a non-penetrating meter across the floor and a probe at the walls to see how far the water traveled.
Remove baseboards and lift planks.Click-lock planks can sometimes be taken up carefully and stacked for reinstall. Glue-down planks usually cannot.
Extract and dry the slab.Standing water on the concrete is extracted, then dehumidifiers and air movers dry the slab and the lower wall.
Check before reinstalling.Concrete holds moisture; readings should be confirmed before the floor goes back down, or the problem returns.

Floating versus glue-down planks after a leak

Floating click-lock

Often removable without damage if done carefully
Underlayment pad is usually discarded and replaced
Drying the slab is straightforward once planks are up

Glue-down

Removal usually destroys the planks
Wet adhesive may need scraping before new flooring
Some contractors try specialty drying through the floor first; ask how they will verify the slab is dry

General information for Aurora, not a quote or professional advice. In an emergency, call 911.