Hardwood flooring is manufactured in many widths and cuts to provide a multitude of design opportunities per species of hardwood. One design element we are seeing become more popular is wood flooring that’s 6” to 10” wide and is chosen for the beauty and presence it brings to a room.
In drier parts of the country and in markets that can experience a dry heating season, a solid flooring in 6” to 10” widths would make just about any installer cringe due to the potential movement that floor could go through. To minimize this movement, many manufacturers have put their wider plank products onto an engineered platform, and have sold them as a more stable option to its solid counterpart. In more humid conditions, that engineered floor may perform better during seasonal changes by not adversely reacting to a higher moisture where a solid floor may show signs of cupping quickly.
For years, the industry has used an image like the one below, stating the use of solid flooring should only be used on- or above-grade. Whereas engineered flooring can be used on all three grades. This is due to the engineered flooring having more dimensional stability to handle the potential of a slightly higher moisture level in a below-grade situation.
To the right are some common types of engineered flooring platforms. If correct living conditions are not maintained in the home, with humidity either being too high or too low, the flooring can be stressed and you may start to see unsightly gaps, squeaks, and pops as fasteners start to work free from the subfloor, and in worst case scenarios, the plies of the engineered flooring starting to tear apart.
While an engineered floor may be able to withstand a slightly higher amount of moisture before showing signs of wood distortion (i.e., cupping or warping), in a dry environment, the structure of an engineered plank will tend to hold together so well that by the time you start to see the signs, it may be too late.
Some of the platforms pictured to the right may handle a wider fluctuation in humidity levels. The manufacturers that utilize these different platforms will have a range in which their product performs best. I have seen many manufacturers’ instructions require maintaining anywhere from 30 percent to 55 percent humidity with a range of 60° to 80° Fahrenheit temperature.
When an engineered plank is exposed to an extended period of dry conditions, the layers of the substrates are stressed, potentially causing irreparable damage to that plank. If held in this situation long enough, the layers can start to peel apart and may appear as “dry cupping.” Internally, the plies are ripping apart and if examined once the plank has been removed, you will see the “wood shear” where the plies have torn.
This issue commonly is misdiagnosed as delamination. The NWFA defines delamination as “the separation of two layers/plies within a piece of engineered flooring due to the lack of an adhesive bond typically is identified as a clean separation at the glue-line.” This would be a complete, clean separation between the plies and not show torn sections as shown in the image to the right. A wood floor that is showing signs of dry cupping or wood shear usually will have moisture content readings that indicate that the flooring has been exposed to very low humidity conditions.
Dry cupping and wood shear are not considered a manufacturer defect and are not covered by the warranty since the environmental conditions of the home were not maintained according to the manufacturer’s maintenance and warranty instructions. More information about dry cupping, wood shear, and delamination can be found in the NWFA’s Problems, Causes, and Cures (C200) technical publication. Here is the phrasing one engineered manufacturer has on their website regarding wood flooring and its reaction to environmental conditions:
“Wood is a product of nature. As a natural material, it will expand and contract as it gains and loses moisture. Some gaps between the boards during low-humidity seasons are normal and not considered a defect. Maintaining optimum humidity levels of 30 percent to 50 percent will minimize these occurrences. Allowing relative humidity levels to fall below 30 percent can result in structural damage to the floor such as large gaps, splits in the surface, distortion of the boards and structural failure.”
Maintaining these correct environmental conditions will keep these issues from happening. Start by having your customers add a thermo-hygrometer in their home to be able to monitor the humidity. If the current HVAC system cannot maintain these conditions, additional moisture control systems may be needed to help keep the temperature and humidity of the home within the manufacturer’s suggested environmental conditions to maintain their warranty.
In addition to utilizing the NWFA for general information, precise information pertaining to the flooring being installed can be acquired from the manufacturer’s installation instructions and/or their care, maintenance, and warranty information. Of which, a copy of that care information should be left with the floor owner to make sure they are aware of how the floor should be maintained, and not just which cleaner should be used. Most manufacturers also have a technical department that will also answer any questions.
For additional information about dry cupping, wood shear, and delamination, check out the NWFA’s Problems, Causes, and Cures at nwfa.org/technical-guidelines/.
Matt Thrane is a training specialist and handles new business development for Gehl Flooring Supply Inc. in Wauwatosa, Wisconsin. He can be reached at matt@gehlflooring.com.
