The age old, and number one, wood flooring complaint is gapping. Gapping is the space between installed boards or strips in wood flooring on either the ends or the sides, usually the long sides of the boards. Gapping is permanent, normal or abnormal, as stated by The National Oak Flooring Association.

Normal gaps are described as seasonal gaps that open in the winter and close in the summer. Winter time brings cold temperatures and low environmental relative humidity and even lower relative humidity in heated buildings. A decrease in relative humidity lowers the wood moisture content resulting in boards shrinking and Shrinking boards produce gaps along the widths of the boards. Should these gaps close, or close to 1/32”, they are considered normal. Normal gaps are not easily noticed from a standing position.

Permanent gaps usually occur during the first year of installation, and are present year round. Permanent gaps will only shrink or enlarge with seasonal changes and are seen from a standing position, but never close. Permanent gapping is most often seen in new construction sites related to building conditions prior to, and during, the installation.

Both the building and the wood flooring material are to be acclimated to ambient or “in use” conditions to minimize gapping. New construction buildings require a minimum of two weeks of indoor environmental acclimation prior to installing hardwood to dry the building to “use” conditions. Construction, whether new or extensive remodel, experiences many wet trades such as painting, ceramic tile installation and texturing. These buildings are high in relative humidity and the sub-floors are usually excessively high in moisture. Should the wood be acclimated and installed to these conditions, the boards shrink leaving abnormal gapping once the building is in use and the heater or air conditioning is turned on. The flooring system also shrinks causing permanent gapping.

Permanent gapping can also occur on existing structures. The wood flooring and building must be in equilibrium and the wood installed at ambient conditions of the site. The definition of ambient is: ff the surrounding area or environment. Meaning the wood must be equal of moisture content to match the indoor environmental relative humidity. Experienced and certified wood flooring professionals know the equilibrium moisture content (EMC) chart giving the needed wood moisture content for all ambient relative humidity conditions. This information can be found at www.nofma.org, www.nwfa.org and the US Department of Agriculture, Forest Products Laboratory. Wood flooring must be acclimated to the ambient conditions of the home.

Wood manufactured wet (higher than acceptable moisture content) will also leave permanent gaps, but the condition will have a different appearance. Acclimation related problems will find gapping throughout the installation where wood manufactured wet will have a more random condition and various board widths. This can only be determined by a certified inspector.

Huge gaps are usually related to movement in the sub-floor panels or a combination of wood planks shrinking and the sub-floor system shrinking. This condition may produce a condition termed “panelizing”. Panelizing is characterized as gaps longer than the length of the boards and following an underlayment panel. These gaps will usually repeat every three or four feet across the room, and even into adjoining rooms. This is a condition often found in new construction and remodel installation sites.

Permanent and abnormal gaps may be the responsibility of the manufacturer, building contractor or the installer.