Noticing checks or splits in your wooden floor is never a pleasant experience, but it is especially disturbing once the floor is new since that is when it is most likely to happen. Splitting is a moisture-related issue — it occurs when wood dries — and a common cause is failure to properly acclimate the flooring boards before setup. Splitting can also happen because the subfloor wasn’t properly framed. As it expands and contracts, the subfloor drives the securely-attached boards to transfer. A damp crawl space under the floor can also cause splitting. Knowing what caused it might help correct it.
Check the room’s humidity. When it’s winter and you’re using the central heating, the humidity might be excessively low. This dries from the top layer of the timber and causes splitting. Run a humidifier in the room to restore moisture into the timber as the growth in humidity may cause a few of the splits to partially heal.
Inspect the crawl area, if there’s one under the floor. Look for signs of dampness like mould on the marks and framing on the ground where heat has dripped. The dampness in a crawl space may seep through the subfloor. The timber may take on such a dampness and later lose it into the room’s air. The outcome is splitting.
Improve conditions from the crawl area by covering the floor with 6 mm black plastic. Overlap the plastic from six inches and tape the seams. Extend the plastic at least six inches up the base walls and tape the edges. Supply ventilation in the form of more base vents or an exhaust fan.
Wait around for a complete season to determine what occurs to the floor if checking develops when it is new. As humidity and temperature conditions change throughout the year, it is normal for new flooring to undergo some adjustment. The splits may close by themselves when the humidity rises.
Inspect the subfloor framing for poorly-connected joists and girders. Adjust them, as required. Instead, hire a professional builder for this job since it will take a trained eye to pinpoint the problem places and framing experience to understand how to correct them.
Fill person splits with an epoxy wood filler that matches the floor color. Epoxy bonds to the wood and stops the splits from widening. Spread the epoxy, using a putty knife. Wipe excess away instantly. Allow it to dry fully. Dab clear finish on the mend, with a rag.