The Laminate That Peaked at the Kitchen Island

Why this matters

A floating floor only works if the whole field can move. Pin it anywhere and the movement that should spread across the floor piles up somewhere else, usually as a peaked seam in the middle of a room. This case is a callback that was diagnosed right the first time, fixed right, and came back anyway the next summer, because the first fix found one pinch point and missed the one doing most of the damage.

The first call

In August a homeowner called about a laminate floor the shop had installed the previous February through an open kitchen and great room. Along one seam in the great room, the floor had risen into a ridge about 6 feet long that flexed and clicked underfoot.

Peaking is two rows pushed up off the subfloor along their shared joint, forming a tent. In a floating floor it means the field is trying to expand and has run out of room: the force has to go somewhere, and the weakest place is a joint line lifting.

 PLAN, NOT TO SCALE. Planks run north-south.

 W wall                                       E wall
 +-----------------------+-----------------------+
 | KITCHEN               :  GREAT ROOM           |
 | [base cabinets]       :                       |
 |                       :          |            |
 |    +------+           :          | peak, 6 ft |
 |    |ISLAND|           :          | along one  |
 |    |screwd|           :          | long-side  |
 |    |thru  |           :          | seam       |
 |    +------+           :                       |
 |                       :  open, no wall here   |
 +-----------------------+-----------------------+
 |<-5 ft->|<4 ft>|<------ 35 ft to E wall ----->|
 |<------------------ 44 ft run ---------------->|

The run is 44 feet east to west, across the plank widths, with no break anywhere. The island stands 5 feet off the west wall and is 4 feet deep, which leaves 35 feet of floor from its east face to the east wall.

The first diagnosis, and why it was right

The first tech checked the perimeter, because peaking is nearly always an expansion problem and the perimeter is where expansion space lives. At the east wall he found it: the shoe molding had been nailed down through the laminate in two places, and the gap behind the baseboard had closed to almost nothing. The floor was pressing against the wall plate.

That is a textbook pinch. Expansion space, per the maker and commonly about 1/4 to 1/2 inch, is hidden by base or shoe and never pinned by a fastener; a nail through the shoe into the floor turns the floor's edge into a fixed point (see related: Expansion Space at Walls and Fixed Objects). He pulled the shoe along the east wall, cut the floor back to restore 1/2 inch, and renailed the shoe into the baseboard only. Over the next three weeks the peak settled down and the seam closed.

Every part of that was correct. The finding was real, the fix matched it, and the floor responded. The job was closed.

The second call

The next July the homeowner called again. Same room, same seam area, a peak again, this time about 8 feet long. The east wall gap was intact; the shoe was still fastened to the base only, and a putty knife slid freely behind it.

That ruled out the first cause returning and said something else was holding the floor still. The second tech, a crew lead, worked the reasoning from the shape of the room rather than from the perimeter.

He cleared two other candidates first, because each would have sent the repair somewhere different.

The house running outside the maker's humidity range. If the floor were simply growing more than any expansion space could absorb, the fix would be the house, not the floor. The maker's instructions gave an in-service humidity range for the warranty; a hygrometer at floor level read 58 percent RH with the air conditioning running, inside it. The homeowner's thermostat history showed no week with the system off. Not the driver.

Water under the floor. A dishwasher or refrigerator line leaking under a floating floor swells the core locally and can lift a seam. The peak was 20 feet from the nearest appliance, the planks at the peak showed no swollen edges, and a pinless meter swept across the peak read the same as planks 10 feet away on either side. Not the driver.

With the room's conditions and water both cleared, what remained was something stopping the field from moving.

The fixed point nobody looked at

A floating floor with nothing pinning it expands outward from roughly its middle. On a 44-foot run, each wall gap takes the growth of about half the run, 22 feet of floor. That is what the maker's expansion space is sized for.

The crew lead pulled the island's toe-kick panel and found the cabinet installer had set the island on top of the finished floor and screwed its base cleats down through the laminate into the subfloor. That made the island a fixed point. Now the floor east of the island could only grow in one direction, so the east wall gap had to absorb the growth of all 35 feet between the island and the wall, against the 22 feet it was meant to handle: 35 divided by 22 is about 1.6 times the movement. When the humid season pushed the field, that growth reached the gap, closed it, and kept coming. Friction from furniture and a heavy sectional sofa resisted the floor's slide, and the force released as a peak partway down the run, before it ever reached the wall.

The first fix had restored the east gap, which bought back enough room for one summer's growth over a normal winter. It could not remove the extra movement the island was forcing toward that wall.

The second finding was the run itself. The plank maker's instructions limited a continuous run in that direction to 40 feet before a break was required (this figure is for this product; read yours). At 44 feet, the floor was over its maker's limit before the island was ever screwed down. The installer had run straight from the kitchen into the great room with no transition, which looks cleaner and is the most common way this limit gets missed.

Read against 'Laminate Floor Peaks At A Seam After A Season Change Decision Tree', both findings sit on the fixed-object and run-length branches. The first call had stopped at the perimeter branch, where the evidence was real.

The repair

Before cutting anything near the island, find what runs through it. Islands carry power for outlets and appliances, and some carry a sink drain and supply lines up through the floor. The crew lead traced both from the basement below and opened the island's back panel before marking a line. The island circuit was turned off at the panel, locked out, and proven dead with a tester checked on a known live circuit before and after (the live-dead-live check NFPA 70E describes), because an oscillating blade near a floor box will find a cable. Power stayed off until cutting was done, then was restored and the outlets were tested with a receptacle tester.

1. Cut the floor free around the island. With a track guide and an oscillating multi-tool, the crew cut the laminate along all four sides of the island, leaving the expansion space the maker requires, here 1/2 inch, between the island and the floating field. The piece under the island stays screwed down; it no longer matters, because the field is no longer attached to it. Cutting laminate throws fine dust from the fiberboard core and its resin: the crew used a tool with dust extraction and wore N95 respirators, with the room's HVAC return covered while cutting and uncovered once the dust was vacuumed up.

2. Cover the gap with trim fastened to the island. Quarter round was nailed into the island's base, never down into the floor. The test: a putty knife slid under the trim between the trim and the floor at several points.

3. Add the break the maker required. The crew cut a straight line across the floor at the kitchen and great room boundary, removed a strip the width of the transition's track, and installed a T-molding whose base fastened to the subfloor in the channel, not to either floor edge. The T-molding's cap overlaps both floors and each side keeps its own expansion space under the cap. That split the run into a 14-foot kitchen field and a 30-foot great-room field, both under the 40-foot limit.

4. Let the peak relax, then check the seam. Once freed, the great-room field could move. The peaked rows dropped over about a week. Two planks along the peak had damaged locking edges where they had been flexed under load for months; the crew replaced them by the method in 'How to Replace One Plank in the Middle of a Floating Floor'.

How it was confirmed

The crew lead set a check for the next humid season instead of closing the job on the day the floor lay flat. The following August: floor flat at the old peak, gaps at both new expansion lines visible behind the trim, T-molding cap sitting level on both sides. The homeowner was also told why the transition was there, because the most likely future failure was a well-meaning handyman caulking it.

What the shop changed

The install had two failures that a cabinet installer and a flooring installer created between them. The shop added two lines to its pre-install sheet: "Island and cabinets: set on subfloor, or floor cut around them with expansion space? Confirmed with the cabinet installer", and "Longest continuous run in each direction, against the maker's limit." On open floor plans the second line now gets measured on the plan, not judged by eye.

References

• The laminate maker's installation instructions: expansion space, maximum run without a break, fixed-object rules.
• See related: Laminate Floor Peaks At A Seam After A Season Change Decision Tree.
• See related: Expansion Space at Walls and Fixed Objects; How to Install Laminate or Rigid Core Floating Floors; Transition Profiles and the Accessible Level Change; How to Replace One Plank in the Middle of a Floating Floor.
• NFPA 70E, current edition, for de-energizing and verifying absence of voltage before cutting near the island's wiring.