Nearly every floor endures some separation between boards. In winter, when homes are heated and the air is dry, wood flooring gives up some of its moisture and therefore shrinks. When that happens, thin cracks appear between. This is normal, and homeowners should be forewarned of this. It is acceptable, and customers should not be calling the installers at the first sign of cracks. Once the indoor heat goes off in the spring, and the indoor environment regains moisture, most of these cracks will close up.
Cracks in winter–in the drier months–may easily develop to the thickness of a dime (1/32 inch) for solid 2 1/4-inch wide strip oak floors.
Floors with light stained woods and naturally light woods like maple tend to show cracks more than darker, wood-tone finished floors.
The cure for cracks? Homeowners should add moisture to the air during dry periods. It’s their choice-live with the cracks and wait until spring, or else add humidity by opening the dishwasher after a rinse cycle, switching off the bathroom fan or hanging laundry to dry in the basement near the furnace. Better yet, install a humidifier in the furnace, or an exterior air vent for the furnace burner.