Nearly every decking endures some separation between hollow composite decking boards. In winter, when homes are heated and the air is dry, hollow composite decking boards 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. Hollow composite decking boards with light stained woods and naturally light woods like maple tend to show cracks more than darker, wood-tone finished floors.