Gaps showing up between your planks six months after install is one of the most frustrating things a homeowner can deal with. Laminate flooring separating is almost never a defect in the planks themselves — it is a sign that something underneath, around, or above the floor is moving. The good news is that once you identify the cause, most separation issues can be fixed without ripping up the entire room. The bad news is that if you misdiagnose it, you will be re-fixing the same gap every spring.
Why Laminate Planks Pull Apart
Click-lock laminate from Pergo, Mohawk RevWood, and Shaw all rely on a tongue-and-groove edge profile that snaps together under tension. When the joint loses tension, you get a visible gap. The four most common culprits, in order of frequency:
- Humidity swings outside the 35 to 55 percent RH range the manufacturer specifies
- Subfloor flatness exceeding 3/16-inch over a 10-foot radius
- Missing or inadequate expansion gap at walls — typically 1/4 to 3/8 inch required
- Heavy furniture or appliances dragging planks apart on a floating install
Roughly 70 percent of separation calls trace back to either humidity or subfloor issues. Track those first.
The Humidity Diagnosis
Most laminate is rated for 35 to 55 percent indoor relative humidity year-round. In a dry Denver winter with the furnace running, indoor RH can drop below 20 percent, which shrinks every plank by a hair. Multiply that hair across 30 planks in a room and you have visible gaps along every seam. Buy a $15 digital hygrometer, log the RH daily for two weeks, and check whether it sits in the spec range.
The fix is a whole-house or room humidifier set to maintain 40 percent. Gaps that appeared from low humidity will partially close on their own once the planks rehydrate, typically within three to six weeks.
Subfloor Flatness and Why It Matters
A click-lock floating floor will telegraph any subfloor dip. When a plank spans a low spot, the unsupported edge flexes downward each time you step on it, slowly working the joint apart. The standard tolerance is 3/16-inch over 10 feet, measured with a long straightedge — not a 4-foot level.
If you find dips over 3/16-inch, you will need to pull the affected planks, skim the subfloor with a self-leveling underlayment like Henry 555 or LevelQuik RS, let it cure for 4 hours, and re-lay the planks. This is the most common fix for separation that keeps coming back in the same spot.
Expansion Gap Mistakes
Laminate expands and contracts seasonally. Manufacturers like Pergo and Mohawk require a minimum 1/4-inch gap at every wall, doorway, pipe, and vertical obstruction. Installers in a hurry sometimes tile the planks tight against a wall, hidden under baseboard or quarter round. When the floor expands in humid months, it has nowhere to go, so the planks bow upward and joints pop apart elsewhere.
To check, pry off the baseboard in a section and measure the gap. If you see less than 1/4 inch, you will need to use an oscillating multi-tool to undercut the wall studs by 3/8 inch or trim the plank edge with a track saw. Refit the baseboard and the floor should relax over the next few weeks.
Step-by-Step Fix for an Isolated Gap
For a gap of less than 1/8 inch in a single joint:
- Tap a tapping block with a rubber mallet from the long side of the loose plank toward the gap, working in 1-foot increments along the seam
- If the gap persists, lift the plank using a suction cup tool, inspect the click profile for chipped edges, and reseat
- For a permanent seal, apply a small bead of Bostik GreenForce or Loctite Quick Set Construction Adhesive along the tongue before clicking back in
- Weight the joint with a 25 lb sandbag for 24 hours while it cures
For gaps wider than 1/8 inch or in multiple planks, the problem is structural — go back to humidity, flatness, and expansion gap diagnostics before patching individual seams.
When to Replace Versus Repair
Mid-grade laminate from brands like Harmonics or Trafficmaster, around $1.29 to $2.49 per sq ft, often uses a thinner click profile that wears out after one or two disassembly attempts. If you have pulled the planks once and the joints already feel loose, replacement is more reliable than repair.
Premium laminate from Pergo Outlast Plus, Mohawk RevWood Plus, or Shaw Repel — typically $2.99 to $4.49 per sq ft with AC4 or AC5 ratings and thicker 12mm cores — holds up to two or three reseats without losing joint tension. These are worth repairing.
When the Whole Floor Needs to Come Up
If the separation is widespread — more than 20 percent of the planks showing gaps, or gaps reappearing within weeks of repair — the floor itself needs to come up. The most common cause is a subfloor that was never properly flattened during the original install, and no amount of plank reseating fixes that. Budget $1.50 to $2.50 per sq ft for disassembly labor, $3 to $5 per sq ft for self-leveling underlayment over the worst zones, and the cost of new flooring since click-lock laminate rarely survives more than one reinstallation cycle without losing joint tension.
For 12mm AC4 or AC5 laminate from Pergo, Mohawk RevWood Plus, or Quick-Step, salvage is sometimes possible if the planks were originally installed within the past 2 years and the click profiles are not visibly worn. For thinner 7mm or 8mm products, plan on full replacement.
Preventing Future Separation
Run a humidifier in winter and a dehumidifier in summer to keep RH between 40 and 50 percent. Use felt slider pads under furniture so dragging does not pull planks apart. Avoid wet-mopping with excess water — a barely damp microfiber mop with Bona Stone, Tile and Laminate cleaner is the safer choice. And before installation, demand the subfloor be flat to 3/16-inch over 10 feet, in writing. That single line in your contract prevents 90 percent of future separation problems.
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