The seasons are a changin’. Cooler air has moved in and some of us have even turned on the heat. Changing temperatures and humidity levels can create some frustrating problems for our hardwood floors. Hardwood Floors Magazine published a great article on this very topic. View the full article here: https://hardwoodfloorsmag.com/2017/10/02/tis-season-understanding-seasonal-related-issues/
Nearly every wood floor will have some seasonal separation between the individual boards – gaps – throughout the floor during the fall and winter months. When the air in the building is heated, the relative humidity levels drop. When this happens, the wood loses moisture as it equilibrates to the drier conditions and boards begin to shrink. As a result, gaps begin to appear between boards. This is a normal phenomenon and is directly related to the reduction of moisture in the surrounding air.
Once seasons change and the interior heating systems are turned off, or when supplemental humidification is introduced and the indoor environment regains moisture, most of these seasonal gaps will disappear.
All solid flooring, including properly specified, manufactured, and installed wood flooring should be expected to have seasonal gaps between boards during the dry months when no supplemental humidification is added.
The width of the boards, the species, and how it’s cut from the log can all affect how much solid wood flooring is affected by this change in moisture. In general, how much solid wood flooring shrinks is directly proportional to its width. For example, in identical scenarios, an 8” wide plainsawn plank of white oak flooring will shrink twice as much as a 4” plank of the same cut and species.
Seasonal gaps between boards are more prominent with solid wood flooring products than with engineered wood flooring products. The structural composition of engineered wood flooring inherently allows it to be more dimensionally stable than solid wood flooring. Although engineered wood flooring is more dimensionally stable than its solid counterpart, it will still react to these low humidity levels but will show itself differently. When the relative humidity levels remain below the manufacturer’s recommendations for long enough, engineered flooring will begin to dry cup. When this happens, the wear layer loses moisture (same as its solid counterpart) and begins to shrink across its outer face, which can exert enough force on the core material to pull the edges of the plank upward. This causes a cupped appearance across the width of the board.
Solid Flooring with Seasonal Gaps
Dry Cupping on Engineered Flooring
The effects of these seasonal fluctuations can be compounded in some new construction scenarios. Energy-conscious homebuyers and homebuilders have, in recent years, demanded tighter, more energy-efficient homes, which can inadvertently become detrimental to wood building components and their ability to perform, if not properly addressed. This construction practice, by design, prevents warm or cool air loss, but also seals in the new home’s moisture. Moisture from the entire building process is not allowed to dissipate quickly enough. This moisture comes from many sources including hundreds of gallons of water used in the placement of concrete, masonry, thin-set, tile mortar, drywall, plaster and many other building components. This will often cause wood flooring and wood subflooring to take on this moisture. When the home dries out and finally finds equilibrium in the home (often 6-12 months after the home has been moved into), the flooring and/or subflooring materials shrink, and again result in what could then be considered abnormal gaps. If the environment remains at these conditions, the gaps will likely never completely close back up in the humid months.
For more information, view the full article by, Brett Miller, Vice President of Education and Certification at the National Wood Flooring Association. https://hardwoodfloorsmag.com/2017/10/02/tis-season-understanding-seasonal-related-issues/