Assessing properties of E. nitens laminated flooring
By Rosie Sargent, Bruce Davy, April 2020.
Download SWP-T097 (pdf)
Worldwide there is increased interest in engineered flooring products, which combine the look of solid wood with increased dimensional stability (i.e. reduced movement in service) and reduced distortion. Specialty Timber Solutions in North Canterbury produce flooring from pruned eucalypts, including Eucalyptus nitens, and have developed two engineered flooring products from E. nitens. The aim of this study was to compare these new products with solid E. nitens flooring, as well as commercially available engineered flooring (European oak with a birch plywood backing), to assess their suitability for an overlay flooring product (either fixed or floating installation). Additionally it was decided to use unpruned pulp regime E. nitens to produce the flooring, as this represents the majority of the E. nitens resource in New Zealand.
Specialty Timber Solutions produced three kinds of flooring from unpruned E. nitens logs – solid, cross-laminated and birch plywood-backed flooring. The performance of these was compared to commercial engineered oak flooring by looking at the board dimensions and levels of distortion at several different ambient humidity levels, and also while soaking one face in water.
When the board moisture content changed, the solid wood flooring changed width significantly more than all the other flooring types. Changes in board width are a major cause of movement- related issues with flooring, so the increased stability of the engineered boards is a significant result. At low moisture content the cross-laminated flooring cupped significantly more than the other flooring types. Cupping tends to only be a problem with floating overlay floors where the board edges are not restrained, and in this situation, it is possible that wide cross laminated boards would cup to an unacceptable extent. Otherwise the dimensions and distortion of the different flooring types were all similar when exposed to changes in air humidity or soaked in water.
The different types of E. nitens flooring all had a similar surface hardness (average ~4kN), which was lower than the engineered oak flooring (average ~5.5kN). This would potentially make the E. nitens flooring more susceptible to damage in service and may therefore make it a lower value product.
The cross laminated E. nitens flooring had the lowest strength and stiffness in third-point bending but was similar to one batch of the engineered oak boards which had a grooved plywood backing (because it is designed as an overlay flooring product). This suggests that the cross-laminated boards are suitable for overlay flooring as intended. The ply-backed and solid wood E. nitens boards had significantly higher strength and stiffness than the engineered oak.
Overall the differences between the engineered oak and E. nitens boards were quite small. The lower hardness of the E. nitens boards may be a disadvantage compared to the oak. In situations where changes in board width need to be minimised, the ply-backed or cross laminated E. nitens were more dimensionally stable than the solid E. nitens, but the cross-laminated boards are more prone to cupping, which may cause issues in service unless adequately glued and nailed to the floor substrate.
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