Evaluation of various engineered wood flooring constructions

Engineered wood flooring is gaining in popularity since it appeared in Europe in the 1970s. In 1999, two-thirds of the wood flooring installed in Europe was engineered wood flooring. The same year, one-third of the wood flooring installed in the United States was engineered wood flooring. Although engineered wood flooring captured this important market share, knowledge of its behavior is still very limited. The variations of hygrometric conditions, occurring during the transition from summer to winter in North America can induce undesirable hygromechanical deformation. The objective of this study was to compare five engineered wood flooring constructions made with North American wood components. The methodology was developed to determine the performance of engineered wood flooring. In accordance with the design parameters selected in this study, the best construction was a 4-mm-thick sugar maple surface layer, an 8-mm-thick white birch core layer, and a 2-mm-thick yellow birch veneer as backing layer. The cupping distortion in black spruce core construction without backing was 20 percent higher than the white birch construction. Constructions made with a white birch core showed a 10 to 40 percent lower cupping distortion than those made with a black spruce core. The varnish layer plays an important role in the performance of engineered wood flooring by reducing the cupping distortion by 50 percent since it limits moisture adsorption through the surface layer. There was no significant difference in the distortion measured for two subsequent conditioning cycles, indicating that the phenomenon occurs in the elastic domain.