Laminate Flooring Lifting at the Seams? Here's Why

Quick Answer

Laminate flooring lifts at the seams when it has no room to expand. The most common cause is missing or insufficient expansion gaps around the room's perimeter — the flooring pushes against the walls and buckles upward. Other causes include moisture underneath the planks, inadequate acclimation before installation, and transition moldings or door frames pinning the flooring down.

Why Laminate Flooring Moves

Laminate flooring is a floating floor — it's designed to sit on top of the subfloor without being attached to it. The planks lock together and the entire floor "floats" as a single unit that expands and contracts with temperature and humidity changes.

This is by design, and it works beautifully — as long as the floor has room to move. When something prevents that movement, the energy has to go somewhere, and it goes up. The seams peak, planks tent, and you get that telltale ridge running along the joints.

The Expansion Gap Problem

Every laminate floor installation guide specifies leaving a gap between the flooring and every fixed object — walls, cabinets, door frames, pipes, and columns. The standard recommendation is 1/4 to 3/8 inch (6 to 10mm) all the way around.

This gap exists specifically to accommodate expansion. In humid conditions or warm weather, the laminate expands. In dry or cold conditions, it contracts. The gap gives the floor room to breathe.

Here's where things go wrong:

The gap was too small or nonexistent. If the installer pushed the flooring tight against the wall, there's no room for expansion. The floor might look fine at first, but the first hot, humid season will cause lifting.

Baseboards or quarter-round were nailed through the laminate. Baseboards should be nailed to the wall, not to the floor. If they're pinned to the laminate, they lock the edge in place and prevent expansion.

Heavy furniture or cabinets sit on the floor. A kitchen island or a fully loaded bookshelf resting on laminate can pin it down, creating a fixed point that prevents the floor from floating freely. Large, heavy objects should sit on the subfloor, not on floating laminate, or the flooring should be installed around them with proper expansion gaps.

Transition moldings are screwed through the laminate. The T-molding at a doorway should attach to the subfloor, not to the laminate. If it pins the laminate down, you've created an immovable point in the middle of the floor.

Moisture: The Other Major Cause

Even with proper expansion gaps, moisture can cause laminate to buckle. Laminate's core is made from high-density fiberboard (HDF), which absorbs water. When HDF gets wet, it swells — and it doesn't shrink back to its original size when it dries.

Sources of moisture damage include:

No moisture barrier. On concrete subfloors, a polyethylene vapor barrier should always be installed beneath the underlayment. Without it, moisture from the concrete migrates up into the laminate.
Spills left sitting. Laminate can handle brief contact with water, but standing water that seeps into the seams swells the core material permanently.
Wet subfloor. A plywood subfloor that wasn't fully dry before installation, or one with ongoing moisture from a crawl space below, will cause problems.
Flooding. Even a minor flood — an overflowing washing machine or a pipe leak — can be devastating for laminate floors.

The Acclimation Issue

Laminate flooring needs to acclimate to your home's environment before installation. The planks arrive from a warehouse at a certain temperature and moisture content. Your home is likely different. If you install the flooring immediately, it will expand or contract after installation to reach equilibrium, potentially causing seam lifting.

Most manufacturers recommend acclimating laminate for 48 to 72 hours in the room where it will be installed. Leave the boxes open (or at least unsealed) so the planks can adjust to the local temperature and humidity.

Skipping acclimation is one of those mistakes that doesn't show up immediately. The floor looks great on day one. A week later, seams start rising.

If you're dealing with moisture-related issues throughout your home — doors sticking in summer, hardwood floors squeaking in winter — managing indoor humidity is the common thread. A hygrometer and a dehumidifier can go a long way toward keeping all your flooring happy.