All the wood in your home will contract or expand according to the moisture in the air. Doors and windows may swell and stick during rainy seasons. In dry, cold weather, cracks and fine lines of separation may appear in wall cabinets and furniture. This is characteristic of wood because wood is a product of nature, and its natural quality is what makes it desirable.

Cracks -The same reaction to humidity or the lack of it is happening constantly in your wood floors. Tiny cracks between edges of boards may appear when dry conditions are produced by your heating system. This can usually be REDUCED simply by installing a humidifier. Both family and floors benefit from a healthier environment and a balance of moisture content in the house.

Squeaks - When interiors become damp in rainy weather, boards may expand so that edges rub together and produce a squeak. Improper fastening of the floor or subfloor can also cause squeaks. To correct this, first try lubrication.

A liberal amount of liquid wax may do the job with waxed floors. Or sift a small amount of powdered soap stone, talcum powder, or powdered graphite between adjacent boards where the noise occurs. Another method is to drive triangular glazier points between the strips using a putty knife to set them below the surface.

If that doesn’t work, drive 2" finishing nails through pilot holes drilled into the face of the flooring. Nails should be placed near edges of the boards. Set them with a nail set and hide with matching color putty.

The best solution requires more work and can be accomplished only where there is access beneath the floor (crawl space or basement). This involves placing wood screws from below. They are inserted through the subfloor and into the finish floor to pull the flooring strips tight to the subfloor. Our association has instructions on doing this and will be glad to furnish you with a copy at no charge.

Source: http://www.nofma.org/