SPC Flooring That Clicks, Gaps or Lifts: Three Symptoms, One Cause
Created on 11.10
Most rigid core flooring complaints are not product failures. They are two site conditions that were never measured.
A rigid core floor is unusually forgiving during installation and unusually unforgiving afterwards. It locks together without adhesive, tolerates a wide range of rooms and goes down fast. That same speed is why problems surface later, in the first heating season or the first dry month, when the floor starts to move.
Three complaints come up more than any others: a click or hollow sound underfoot, joints that open into visible lines, and edges that lift along a wall. They look like three separate faults and are usually treated as three separate claims. In most cases they trace back to the same two conditions.
Symptom 1: The click underfoot
A hollow click when you walk across a plank almost never means the locking profile is defective.
Rigid core planks are stiff. They do not settle into small hollows the way a flexible floor would; they bridge them. Bridge a stiff plank over a dip and the middle of that plank is unsupported. Load it and it deflects, then releases — which is the click you hear, and the movement that slowly works the joint loose.
The diagnostic is simple and does not need tools you don't already have on site:
Walk the floor in bare feet or socks, slowly, heel first. Locate the exact planks that click and mark them.
Put a straightedge across those planks in both directions, in several positions. If the deflection happens at the same place each time, the issue is beneath the floor.
Press down on the plank with one hand while a second person walks past. If you can feel movement under your palm, the plank is not bearing on the substrate.
What you are looking for is not "rough concrete". It is a local high or low point that a stiff board cannot follow.
Symptom 2: The joint that opens
An open joint at an end seam, appearing weeks after installation, is usually read as a manufacturing fault. It is more often a floor that had nowhere to expand.
Rigid core expands and contracts with temperature more than most people expect, and it does so as a whole field rather than plank by plank. If the field is trapped — pinned at a doorway, wedged under a skirting board, butted tight to a wall on all four sides — the movement has to go somewhere, and it goes into the weakest point in the field: a joint.
Two things separate a joint failure from a product failure:
Pattern. Product faults tend to concentrate in one batch and one area. Movement faults follow geometry: they appear along the longest run, at the end of a corridor, or at the transition where one room meets another.
Timing. A joint that opens in the first heating season or the first dry spell is behaving like a floor, not failing like a product.
Symptom 3: The edge that lifts
Edges lift along walls and at doorways for a reason that is easy to see once the skirting is off: the plank is touching something it should not.
Three common versions:
The plank was laid tight to the plaster and the skirting was fitted down onto it, so the floor is pinned on that side.
A door frame or threshold was undercut too little, and the plank is trapped beneath it.
The skirting was fixed with a heavy bead of adhesive that bridged the gap and grabbed the floor surface.
In all three, the floor has been converted from a floating surface into a restrained one. The lift at the edge is the visible end of that restraint.
The diagnostic table
What you see | Most likely cause | How to confirm on site |
Click or hollow sound at specific planks | Local flatness deviation under a stiff board | Straightedge across the affected planks; movement felt under the palm while someone walks |
Sound across the whole room, not localized | Underlay or substrate that is itself soft or loose | Check for a compressible layer under the planks; test whether the substrate sounds drummy when tapped |
Joints opening along the longest run | Insufficient expansion at the perimeter or through a doorway | Remove a skirting section; check whether the plank edge is tight to the wall |
Joints opening in one small area only | Batch or locking profile damage from forced installation | Inspect the locking edge of the affected planks for crushed or whitened tongues |
Lift along one wall | Floor pinned by skirting, adhesive or threshold | Lift the skirting; look for contact between plank edge and wall or fixings |
Lift at a doorway or radiator pipe | Undercut too shallow; pipe sleeves not used | Inspect the cut around the frame or pipe; check for contact |
Gap appearing at a transition strip | Transition fixed to both sides instead of one | Check whether the profile is screwed into both floors |
Read the table by row, not by symptom name. The same visible gap can sit in two different rows, and the fix is different.
Why it comes back to two measurements
Almost every row above resolves into one of two numbers, neither of which is printed on the box:
How flat the substrate is. Not "level" — flat. A floor can be perfectly level and still have hollows. Rigid core needs a substrate that does not let a plank bridge and rock.
How much room the floor has to move. Not "a gap somewhere" — a continuous gap at every fixed element, and a break in the field wherever the floor passes through a doorway.
If both are right, most of these symptoms never appear. If either is wrong, the floor will find the weakest point in the installation and show you where it was.
How to check flatness before the boxes arrive
This is the step most site teams skip, because it costs an hour and produces an argument.
Clear the room. Flatness cannot be judged around stored materials or protection boards.
Use a straightedge, not your eye. A two-metre straightedge laid in several directions across the room is the standard site method. Mark where it rocks and where light passes under it.
Record the results on a plan, not in your head. Note the position and size of each deviation. This is what you will use to decide between self-levelling compound, patching, or a different floorcovering.
Check the substrate as well as its shape. A screed that sounds hollow when tapped, or that crumbles at a scratch, is a different problem from one that is merely uneven.
Ask your supplier what tolerance their product is installed to. This is the number that matters, and it belongs in the installation guide, not in a general article. Take it from the document for the exact product and thickness you are buying.
If you are buying flooring for a project and the installer has not asked for that tolerance, that is the moment to ask why.
Where the floor needs room
Expansion is not one detail at one wall. It is a continuous condition around the whole perimeter, and it has to be maintained at every point where the floor meets something fixed.
At walls. The plank edge stops short of the plaster. The gap is then covered by the skirting, never filled. Filling it with sealant or grout converts a floating floor into a restrained one.
At doorways. A field that runs from one room into the next needs a break at the opening, or a transition that is fixed on one side only. A threshold screwed down on both sides pins the floor at the most heavily trafficked point in the building.
At door frames and architraves. The frame is undercut so the plank slides beneath it with clearance, not so it fits tightly. A tight fit here is one of the most common causes of a lift that appears metres away.
At pipes and columns. Sleeves and collars, not a snug hole. Any rigid element passing through the floor needs a clearance around it.
Under heavy fixed furniture. A kitchen island or a built-in wardrobe bearing on the floor is a restraint. Either the floor stops at the unit, or the unit is installed with clearance and a matching skirting detail.
Temperature, sunlight and the room you did not think about
Movement is driven by temperature as much as by moisture, which is why the failures often appear in specific rooms rather than across a whole house.
A south or west-facing room with full-height glazing will run hotter at the floor surface than the room two doors away. A floor laid in a cool spring, with tight joints and no perimeter gap, will often be the one that complains first when that room reaches summer temperature.
Two practical consequences:
Do not install a floor into a cold building and then immediately heat it to full working temperature. Let the material and the building reach something close to normal service conditions first.
When a client reports a problem in one room only, ask what that room does that the others do not. The answer is usually sunlight, underfloor heating, or a door that is always shut.
What to check before you order
A short list, in the order it should happen:
Measure flatness and write it down, before the flooring is ordered — not after it is delivered.
Confirm the flatness tolerance for the exact product and thickness, from the installation guide.
Confirm who is responsible for substrate preparation. This is the single most common gap between a flooring supplier and a main contractor.
Confirm the perimeter detail with the skirting or shadow-gap design. A shadow gap looks clean and hides nothing — the expansion gap still has to exist behind it.
Confirm what happens at every doorway, threshold and fixed unit on the plan.
Keep one box from the delivered batch, unopened, with its label. If a joint problem appears later, the batch number is what makes a claim possible.
If the floor is already down
The order of investigation matters more than the tools:
Step 1 — Decide whether the problem is local or global. Mark the affected area on a plan. A single room, a single run, or a single wall changes the diagnosis completely.
Step 2 — Take the skirting off one wall in the affected area. This is a fifteen-minute job that answers the expansion question directly. Either there is a gap, or there is not.
Step 3 — Check the flatness of the affected area, not the whole floor. If the click is in one place, measure that place.
Step 4 — Photograph before you repair. The same evidence discipline that applies to a delivery claim applies here: the position, the joint, the batch label, and the wall edge with the skirting removed.
Step 5 — Only then decide between a local repair and a relay. A single lifted edge is often a skirting and clearance fix. A field that has opened along its longest run is a perimeter problem and will come back if only the joints are closed.
FAQ
Why does my SPC floor click only in some places?
Because the substrate is not uniformly flat. A stiff plank bridges a hollow, deflects when loaded and releases — the sound is that movement, not the locking profile.
Can I fix open joints by tapping them back together?
You can close them, but they will reopen if the floor still has nowhere to move. Close the joint only after the perimeter and doorway conditions have been corrected.
Is a hollow sound always an installation fault?
Not always. A compressible underlay, a loose screed or a detached self-levelling layer can all produce it. The difference is whether the sound is localized or spread across the room.
Do I need an expansion gap if the room is small?
Yes. The gap is not proportional to room size in the way people assume; it exists because the floor is a floating field and every fixed edge restrains it.
Does underfloor heating change the diagnosis?
It changes the amount of movement, not the principle. The same two conditions apply, and the perimeter detail becomes more critical, not less.
Can a supplier tell from photos whether it is a product fault?
Sometimes, and only with the right photos: the locking edge in close-up, the batch label, the wall edge with skirting removed, and a wide shot showing where in the room the problem sits. Photos of a gap alone are not enough to separate a product fault from a movement fault.
The short version
A rigid core floor is a floating field. It works when the surface beneath it is flat enough for stiff planks to bear on, and when the field has somewhere to go at every fixed edge. Almost every click, gap and lifted edge is one of those two conditions showing up in a different place.
Neither condition is a product specification. Both are site decisions, and both are cheap to get right before the boxes are opened.
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