Gaps between boards are one of the most common complaints from people with hardwood floors. It is normal for these cracks to appear in the winter months, and fade away in the summer months. Properly made and installed flooring is expected to have seasonal cracks between the boards of the flooring. The size and the severity of the gap depend on a number of factors.
Seasonal cracks in hardwood flooring are caused by moisture change in the environment. In the winter, the heating unit drastically reduces the natural moisture in the house. As your furnace heats the air it also dries it. Eventually all the air in the home becomes extremely dry. Over the course of the heating season moisture is naturally drawn out of the wood and into the dry air. As the wood loses moisture it begins to shrink in size resulting in cracks between the boards of your flooring.
The size of the gaps depends on a number of factors. The most important factor is the amount of moisture change in the flooring from one season to the next. The greater the moisture differential, the larger the gap will be. The next factor is the width of the flooring. Wood will shrink or swell with moisture change as a percentage of its width. A 2-1/4” wide flooring may experience a seasonal gap of heavy 1/32” between the boards, and a 9” wide plank may show seasonal movement over 3/16”. Basically, the wider the plank, the larger the gap. Another factor is the specie of wood from which the flooring is made. Some species shrink or swell more than others when exposed to the same moisture change. As a rule of thumb, hardwoods tend to move less than softwoods.
There is only one way to eliminate seasonal gaps. Keep the moisture content in the wood consistent year-round. There are many methods to help achieve a consistent moisture level, some more practical than others. The most effective method is to have a humidifier installed on your furnace unit. A humidifier will introduce moisture to the forced air system. The furnace will then distribute the moistened air throughout your home. Other ways to introduce moisture include: running a portable humidifier, hanging damp clothes around the house to dry, and boiling water on the stove. If you have a large area of flooring, the latter methods will not introduce enough moisture to make a noticeable difference. Always monitor the moisture level in your home. If you introduce an excessive amount of moisture you will cause damage to many areas of your home. If you have excessive condensation on your exterior windows or doors, you have too much moisture.
Abnormal gaps do not close after the end of the summer season. These abnormal gaps can be caused by a variety of things. The most common cause is due to the flooring absorbing excess moisture right before, during, or just after installation. This moisture comes from recently used building materials that have not had a chance to properly dry. Freshly done drywall, plaster, paint, tile, and concrete are huge sources of excess moisture. This is usually combined with framing lumber that has not had a chance to dry to cause severely high moisture levels. When kiln-dried flooring is placed in a home under these conditions it acts like a sponge. The flooring will soak up the excess moisture and swell in size. If the flooring is laid at this slightly larger than normal size, it will drastically shrink during the first heating cycle. The flooring will never return to the size it was installed at because the moisture will never be that high again, and there will always be gaps between the boards. The gaps will be larger in the winter and smaller in the summer, but most likely always be there. To avoid this problem, run a de-humidifier to reduce the ambient moisture level before having the flooring delivered. Another cause for abnormal gaps is over-drying. This is usually caused by a wood burner or a fireplace. If you have this type of heat it is essential to add moisture to the environment to prevent damage to your floor. Another common cause of abnormal gaps is house or foundation settlement. When outside walls settle, or the center support beams move, the area of the floor actually stretches. The most noticeable gaps are usually over a joint in the sub-floor.
Abnormal gaps can be repaired so the cracks nearly disappear. The best time to repair cracks is midway between seasonal extremes. This is usually during the months of April or October. Using a color-matched filler suitable for hardwood flooring is the best way to camouflage the gaps. The floor may or may not need sanded down and refinished. This depends on the current condition of the gaps and the quality of the finish on the flooring. When properly repaired, abnormal gaps are almost unnoticeable and generally lost in sight. If the gaps are truly abnormal, the filler should remain in the gaps during repeated seasonal changes.
Gaps in flooring are common, and can add to the natural beauty and rustic feel of real hardwood flooring. If you do not want to lessen the appeal of natural wood flooring, let the summer environmental moisture close the gaps naturally. If you do not want to see the normal gaps, adding moisture during the heating season will reduce the appearance of them.
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