Laminate flooring is a popular choice in New Zealand homes thanks to its durability and good looks, but it can develop an annoying problem: lifting, buckling, or peaking along the joints. Understanding why this happens is the first step to fixing it — and preventing it from coming back.
What Does 'Lifting' or 'Peaking' Actually Mean?
When laminate planks push upward at the seams or edges, installers call it peaking or buckling. You might notice a ridge running along a joint, or whole sections of the floor bowing up off the subfloor. In severe cases, planks can separate or crack. It looks bad and can become a trip hazard, so it's worth sorting out promptly.
The Most Common Cause: Moisture
Moisture is by far the leading culprit. Laminate is made from a high-density fibreboard (HDF) core that swells when it absorbs water. In New Zealand's varied climate — from the humid north to the damp, cold south — moisture can enter from several directions:
- Subfloor moisture: Concrete slabs can release moisture vapour, especially in older homes or those built on low-lying ground. Without an adequate moisture barrier (also called an underlay membrane), this vapour is absorbed directly into the planks.
- Spills and leaks: A slow leak from a dishwasher, fridge water line, or bathroom can saturate planks before you even notice.
- High indoor humidity: Poor ventilation, drying laundry indoors, or inadequate subfloor ventilation can raise ambient humidity enough to cause swelling over time.
- Wet mopping: Using too much water when cleaning laminate is a common mistake. Always use a damp — not wet — mop.
BRANZ research highlights subfloor moisture as a persistent issue in NZ housing, particularly in homes without adequate underfloor ventilation.
Missing or Insufficient Expansion Gaps
Laminate flooring is a floating floor — it is not fixed to the subfloor and must be free to expand and contract with temperature and humidity changes. Every installation requires an expansion gap (typically around 8–12 mm) around the entire perimeter of the room, including around door frames, pipes, kitchen islands, and any fixed object.
If this gap is missing or too small, the floor has nowhere to go when it expands. The planks push against the wall or obstacle and the only direction left is up — causing peaking along the joints.
Common mistakes that eliminate expansion gaps include:
- Skirting boards or scotia moulding nailed directly through the flooring into the subfloor
- Underlay or planks running tight against the wall
- Heavy furniture placed hard against the wall, pinching the floor
- Door frames not undercut to allow the floor to slide underneath
Poor Subfloor Preparation
Laminate requires a flat, dry, and stable subfloor. Most manufacturers specify a flatness tolerance — commonly no more than about 3 mm variation over a 1.8 m span, though always check your specific product's technical data sheet.
High spots or dips in the subfloor create uneven pressure on the planks. Over time, this can cause joints to lift or planks to flex and separate. Concrete subfloors should be checked with a long straightedge and ground down or filled (using a suitable self-levelling compound) before installation begins.
Incorrect or Missing Underlay
Underlay serves multiple purposes: cushioning, acoustic dampening, and — critically — acting as a vapour barrier over concrete. Using the wrong underlay, skipping it entirely, or failing to tape the joins properly can allow moisture to reach the planks from below. Always use an underlay rated for your subfloor type and check that it meets the flooring manufacturer's requirements.
Temperature Extremes
Laminate expands in heat and contracts in cold. In rooms that get very warm — a sunroom or conservatory, for example — or that experience large temperature swings, the expansion forces can be significant. This is why laminate is generally not recommended for outdoor areas, uninsulated sunrooms, or in front of large west-facing windows without adequate UV and heat management.
Comparing Common Causes at a Glance
| Cause | Typical Sign | DIY Fix Possible? |
|---|---|---|
| Missing expansion gap | Peaking near walls or fixed objects | Often yes — remove skirting, recut gap |
| Subfloor moisture | Widespread buckling, swelling | Partly — fix source, may need relay |
| Wet spill or leak | Localised lifting near appliance | Fix leak first, replace affected planks |
| Poor subfloor flatness | Uneven peaks across the floor | Subfloor prep needed before relay |
| Wrong or missing underlay | General instability, moisture damage | Relay with correct underlay |
| High indoor humidity | Gradual, widespread swelling | Improve ventilation, use dehumidifier |
How to Fix a Lifting Laminate Floor
- Find and fix the moisture source first. There is no point reinstalling a floor if the underlying problem remains.
- Check expansion gaps. Remove skirting boards and inspect. If planks are tight against the wall, carefully trim the edge planks to restore the gap.
- Allow the floor to dry. If moisture has caused swelling, give the floor time to dry out in a well-ventilated space before deciding whether planks need replacing.
- Replace damaged planks. Badly swollen or delaminated planks won't recover — they need to be replaced. Keep a few spare planks from your original installation for this reason.
- Relay with correct preparation. If the problem is widespread, a full relay with proper subfloor prep and underlay is often the most cost-effective long-term solution.
When to Call a Professional
If the lifting is widespread, if you suspect a plumbing leak (which is restricted work requiring a licensed plumber — see the Plumbers Gasfitters & Drainlayers Board), or if the subfloor itself is damaged or uneven, it's time to bring in a qualified flooring installer. A professional can assess the subfloor, identify moisture sources, and relay the floor correctly. You can find experienced local flooring installers on tradedirectory.co.nz.
If your home is a rental, note that the Healthy Homes Standards require adequate subfloor moisture barriers and ventilation — a landlord may have obligations to address underlying moisture issues.