Choose to Reuse contracted with the Oregon Wood Innovation Center at Oregon State University to assist with a project to evaluate performance and ‘reclaimability’ of flooring based on installation substrate and method. Twelve 4’x8’ French oak floor mock-ups were created by installing flooring on plywood and concrete substrates using combinations of nails, screws, adhesives, and with and without moisture barriers. Floors were cycled through low humidity and high humidity conditions and stability was assessed via measuring swelling in width, cup/crown across the width, and splitting was assessed visually. Following testing, all floors were then deconstructed. Time to remove the materials was measured as was a visual estimate of the yield of usable flooring. The process is described below through a series of images.

Portable heaters and dehumidifiers were placed in each hoop house and run 24 hours a day, 7 days a week to condition the flooring to a low moisture content. Temperature was approximately 84°F and RH was 25%. The moisture content (MC) of the flooring was checked daily with a moisture meter for approximately 3 weeks. After this time, MC was approximately 8 to 10% and day-to-day changes were minimal. Measurements were taken, boards were numbered and an Excel spreadsheet created so that every board number could be linked to hoop house, substrate, and installation system. Boards were also marked across the width with a black line to indicate the specific location for measurement of cup/crown. Photos were taken of each board with a measuring tape placed within the image to document locations and dimensions of any splits or other defects.

Following these initial measurements of board dimensions and defects, humidifiers were then placed in each hoop house and run constantly. After approximately 2 weeks of exposure at 72°F and 75% RH, boards had stabilized to a moisture content of approximately 13 to 16%. Measurements were taken again to determine width and cupping/crowning again. For consistency, crown was measured by placing the straight edge on the surface and measuring the gap on the right side of the straight edge; the value was reported as negative to contrast with cupping (which again was recorded as a positive value). Photos of each board were captured again.

This project was primarily focused on answering two related questions: 1) How does installation method affect flooring performance (in terms of stability) and 2) How does installation method affect reclaimability? The results indicate that the two (stability and reclaimability) may be mutually exclusive to some extent. This is not entirely unexpected in that we might assume that a more rigid installation method that provides maximum restraint and hence stability is also likely to lead to flooring that is more difficult to remove without damaging the flooring and/or the subfloor. With regards to stability, there were no apparent significant differences in performance in swelling between any of the installation systems on concrete or flooring installed on plywood with nails. However, Bostik Greenforce appears to provide significant stability with respect to swelling in width when used on a plywood substrate. These experiments showed that superior performance from the standpoint of stability came at the expense of reclaimability. The Bostik Greenforce adhesive on both concrete and plywood resulted in floors that were difficult (or near impossible) to deconstruct without significant damage to the flooring and subfloor. All other floor installations were reclaimable with minimal damage. The installations that installed using nails or screws required the least amount of time and effort by far and resulted in the least damage. However, the degree of reclaimability could not be assessed within the scope of this study. Based on the results of this study, we would recommend installing flooring either directly on concrete with a moisture barrier and Bostik Best adhesive or installing on plywood over concrete with a moisture barrier and Sika AcouBond adhesive.

In summary, based on the results of this study, for enhanced stability and reclaimability we would recommend installing flooring either directly on concrete with a moisture barrier and Bostik Best adhesive or installing on plywood over concrete with a moisture barrier and Sika AcouBond adhesive. Swelling is similar for these installation methods (and for all those tested, in fact) however cupping is installation methods tested. Further, these systems allowed for adequate deconstruction with minimal damage and hence reclaimability of the flooring. At the same time, it must be recognized that the time and effort to remove flooring installed via these adhesive-based systems is much greater than with methods requiring only screws or nails.