First rule: fix the moisture source
Wood is hygroscopic — it constantly takes on and gives off moisture to match the air and surfaces around it, swelling when it gets wetter and shrinking when it dries. That single fact is behind most of the problems on this page: cupping, crowning, gapping and buckling are all the timber moving as its moisture content changes.
So the universal first step for any moisture-related problem is the same: find and fix the source of the moisture before you attempt any repair. Sanding, filling or recoating a floor while it is still wet just locks the damage in — and often creates a second problem on top of the first. Use a moisture meter if you can, check for leaks, drainage, subfloor ventilation and indoor humidity, and let the floor return to a stable moisture content before deciding what to do.
Be patient. Minor cupping and seasonal gaps very often self-correct once humidity normalises and the timber re-equilibrates. Many floors are sanded too soon, turning a problem that would have fixed itself into a permanent one. Dry first, assess later.
Cupping — edges higher than the centre
What it looks like
Each board dips slightly in the middle and rises at its long edges, so the floor feels like a series of shallow troughs and you can catch the board edges underfoot or with a straightedge.
The cause
Cupping is a moisture imbalance: the underside of the boards is wetter than the top surface. The bottom swells, the top stays put, and the edges are forced upward. Typical sources are a damp or poorly ventilated subfloor, a slow plumbing or appliance leak, a concrete slab that was not fully dry before laying, or sustained high indoor humidity.
How to fix it
Fix the moisture source first — that is non-negotiable. Then let the floor dry slowly and evenly and give it time to flatten on its own. Only once it has fully dried and stopped moving (verified with a moisture meter) should a persistent cup be sanded flat. Sanding while still damp is the classic cause of crowning later.
How to prevent it
Keep subfloors ventilated and dry, fix leaks promptly, ensure slabs are cured and tested before laying, and keep indoor humidity in a stable range. More on day-to-day floor care →
Crowning — centre higher than the edges
What it looks like
The opposite of cupping: each board is higher in the middle than at its edges, so the surface reads as a series of gentle humps.
The cause
Crowning often follows cupping. If a cupped floor is sanded flat before it has fully dried, the raised edges are removed while wet. When the boards finally dry and shrink back to a flat profile, the centres are now proudly high — crowned. It can also come from moisture reaching the top surface of an already-flat floor.
How to fix it
As always, stabilise the moisture content first and let the boards reach equilibrium. Once the floor is genuinely dry and stable, it can be sanded flat — this time the result will hold because the timber is no longer moving.
How to prevent it
Never sand a cupped floor until it has fully dried and flattened. Patience after a moisture event is the single best preventative — rushing the sand is what creates crowning in the first place.
Gapping — winter gaps between boards
What it looks like
Thin gaps open up between boards, most noticeably in winter or in heated, dry rooms. You may see lines of daylight or trapped dust along the joints.
The cause
Dry indoor air. When heating lowers the relative humidity, the boards lose moisture and shrink, pulling apart slightly along their edges. This is normal seasonal movement for solid timber, and the gaps usually close again in more humid months.
How to fix it
For seasonal gaps, the best fix is usually none — they close on their own as humidity rises. If you want to reduce them, stabilise indoor humidity with a humidifier. Permanent, year-round gaps that never close can be filled (best done in the dry season when gaps are widest) or, for large gaps, splined with thin timber slivers.
How to prevent it
Keep indoor relative humidity stable — broadly 40–60% — across the seasons, and avoid letting rooms swing between very humid and very dry. Stable humidity is the answer to both gapping and cupping.
Buckling & lifting — severe moisture
What it looks like
The most dramatic moisture problem: boards lift clear of the subfloor, tent up, or pull away from the wall. This is well beyond cupping.
The cause
Major or prolonged water exposure — flooding, a burst pipe, or a long-running leak — combined sometimes with a floor laid without a proper expansion gap. The timber swells until it has nowhere left to expand and forces itself upward.
How to fix it
Stop and dry the water immediately, then let the floor dry thoroughly. Minor buckling can occasionally settle back as the floor dries, but distorted, lifted or split boards generally have to be replaced and the area refinished to blend in. This is usually a job for a professional.
How to prevent it
Respond to leaks and floods fast, ensure the subfloor and slab are dry before laying, and always leave the correct expansion gap around the perimeter so the floor has room to move.
Cloudy, white or hazy finish
What it looks like
Milky, white or foggy patches in the coating — sometimes a localised ring, sometimes a haze across a whole area. The wood underneath is usually fine; it is the finish that has gone cloudy.
The cause
Trapped moisture is the usual culprit: water that got under or into the finish, a coat applied over a surface that was not fully dry, or "blushing" from finishing in cold, humid conditions. A milky haze can also come from wax or polish build-up, or from steam-mopping forcing moisture into the coating.
How to fix it
Light blushing or moisture haze sometimes clears as the finish fully dries — give it time first. If it persists, the affected area needs to be screened and recoated. A wax or polish build-up haze is different: it has to be stripped with the appropriate cleaner before recoating. How a screen-and-recoat works →
How to prevent it
Make sure every coat goes onto a fully dry surface in suitable conditions, never steam-mop a wood floor, and clean only with a pH-neutral wood-floor cleaner rather than wax or all-purpose sprays.
Peeling or flaking finish
What it looks like
The topcoat lifts, flakes or peels away in patches, leaving the layer or bare timber beneath exposed. It often appears first in high-traffic areas.
The cause
An adhesion failure. The finish never properly bonded to what was beneath it — usually because of surface contamination (wax, polish, oils, cleaning residue), inadequate abrasion before recoating, or a topcoat applied over an incompatible product. Recoating over the wrong existing finish is a frequent cause.
How to fix it
Peeling can rarely be patched invisibly because the bond has failed across the area. The affected zone — and often the whole room for an even result — needs to be sanded back to remove the unbonded coating, then refinished with a compatible product over a clean, properly abraded surface.
How to prevent it
Before any recoat, clean thoroughly to remove all contaminants, abrade the surface properly so the new coat can key in, and confirm the new finish is compatible with the old. When in doubt, test a small area first. Compatibility of finish types →
Scratches, dents & pet marks
What it looks like
Surface scuffs and fine scratches, deeper gouges that catch a fingernail, dents from dropped objects or heels, and clusters of fine claw scratches from pets — typically near doors and along runways.
The cause
Grit dragged across the surface, hard impacts, and pet claws. Most "damage" is actually only in the finish layer, not the timber, which is good news for repair.
How to fix it — match the repair to the depth
- Spot-repair light scratches that sit only in the finish with a touch-up kit or finish-repair pen.
- Buff-and-recoat (screen-and-recoat) when the whole floor looks tired and scratched but the coating is still intact — this refreshes the surface with no full sand-back.
- Full sand and refinish when scratches and dents reach the bare timber, the wood has gone grey, or traffic lanes are worn through. The full refinishing process →
How to prevent it
Mats at entrances to trap grit, felt pads under furniture legs, keeping pets' claws trimmed, and regular sweeping or vacuuming so abrasive grit never gets ground in.
Squeaks & creaks
What it looks like
A squeak or creak underfoot in specific spots, often worse in dry months when boards have shrunk slightly.
The cause
Movement. A board rubbing against a neighbour or a nail, or the floor flexing against a subfloor it is no longer tightly fixed to — loose fasteners, a gap between subfloor and joist, or seasonal shrinkage all let parts move and rub.
How to fix it
If you can reach the underside (from a basement or crawl space), shimming the gap between subfloor and joist or adding a fastener is the cleanest fix. From above, the floor can be re-secured into the joists, and lubricating powders worked into the joint can quiet minor squeaks. Persistent or widespread squeaks point to a subfloor or fixing issue worth a professional's eye.
How to prevent it
Sound fixing at installation and a flat, well-fastened subfloor prevent most squeaks. Keeping humidity stable also limits the seasonal shrinkage that lets boards move and rub.
Fading & colour change
What it looks like
The floor lightens, darkens or shifts in tone over time — most obviously as a sharp line where a rug or furniture has shielded one area while the rest changed colour around it.
The cause
Sunlight. UV and visible light gradually change the colour of both the timber and some finishes — many woods mellow or amber, while a few darken. It is a natural ageing process, not damage, but uneven exposure makes it obvious.
How to fix it
Colour change is in the wood itself, so it cannot be wiped off — evening it out means letting the shielded areas catch up, or sanding back and refinishing for a uniform tone. Rearranging rugs and furniture periodically lets the whole floor age evenly.
How to prevent it
Manage the light: blinds, curtains or UV-filtering window film cut the exposure, and moving rugs around prevents hard tan lines. Full guide to sunlight and floors →
Frequently asked questions
Why is my wood floor cupping?
Cupping — edges higher than the centre — is almost always a moisture problem: the underside of the boards is wetter than the top, so the bottom swells and pushes the edges up. Common sources are a damp or unventilated subfloor, a leak, a slab that was not fully dry, or high indoor humidity. Find and fix the moisture source first; sanding before the floor has dried and flattened causes crowning later.
Will cupping go away on its own?
Often, yes. Minor cupping from a temporary humidity swing usually flattens by itself once the moisture source is removed and the timber re-equilibrates with the room, which can take weeks or months. Be patient — let the floor dry and stabilise before deciding on any repair. Only cupping that persists after the floor has fully dried needs sanding.
Why does my floor have gaps in winter?
Wood shrinks as it dries. In winter, heating dries the indoor air and the boards contract, opening thin gaps between them. These seasonal gaps usually close again in more humid months and are normal for solid timber. Keeping indoor relative humidity stable (broadly 40–60%) reduces the movement. Only permanent gaps that never close need filling.
Why is my floor finish cloudy or white?
A cloudy or white patch is usually trapped moisture — water under or in the coating, a coat applied over a surface that was not dry, or blushing from finishing in cold, humid conditions. Wax build-up and steam-mopping can also cause a milky haze. Light blushing sometimes clears as it dries; persistent cloudiness needs the area screened and recoated, or the wax build-up stripped.
Can scratches be fixed without sanding the whole floor?
Light scratches that sit only in the finish can be spot-repaired with a touch-up kit or blended away with a buff-and-recoat, with no full sand-back. Deep scratches and dents that reach bare timber, or worn traffic lanes, are better corrected by a screen-and-recoat or, if the wood is damaged or grey, a full sand and refinish. Match the repair to the depth of the damage.
What causes a wood floor to buckle?
Buckling — boards lifting off the subfloor — is the most severe moisture problem and usually follows flooding, a major leak, or a floor laid with no expansion gap. Excess moisture swells the boards until they have nowhere to go but up. Stop and dry the source immediately; minor buckling can settle as the floor dries, but lifted boards generally need replacing and refinishing. Always leave the correct expansion gap.