NWFA Tip Sheet: Engineered Flooring Issues
March 22, 2010
I recently reviewed a walnut veneered engineered floor, approximately 1,200 square feet, where the reported issue was excessive denting and scratching. Upon arrival at the site, the home owner pointed out small dents in the face of the flooring mainly in the traffic areas. He also pointed out in the same areas were scratches that crossed flooring planks. (Photos 1 and 2) The owner reported the condition had occurred over time since the flooring was installed about a year ago. The dialogue between the flooring contractor and home owner had broken down. The contractor had looked at the issues and said it was the wood’s fault and, as reported, ceased to return any calls. The owner was poised for litigation. The owner’s lawyer was present during the review.
The review began with overall observations of the installation and any conditions that were abnormal. Overall, the flooring was generally flat with occasional high areas and low areas. The boards themselves were flat without cupping or crowning. Boards were well adhered with no significant hollow spots or movement. Boards were together with only an occasional small gap along an edge or end. Multiple nine-board measurements were consistent throughout the installation at 45” to 45 1/16”. Measuring the size of the dents and pock marks in the flooring showed most were about 1/8” x 1/8” to 3/16” x 3/16”. (Photos 2 and 3)
The commissioners, owner and lawyer had originally asked that I give them information as to any merits to the issues involved. I could give the following information: there were no apparent issues with the flooring installation, the flooring integrity, or the site conditions. The size of the marks showed that for a comparable solid wood product, denting could occur with similar spot loading from 16 lbs to 36 lbs per square inch based on the mechanical properties for walnut found in The Wood Handbook: Wood as an Engineering Material. (Illustration 4) The scratches with an even smaller area involved, could be made with a lighter load. This meant that for a small pebble under a shoe, exposed shoe nail, or the like, denting is possible. Also, there is no standard that engineered wood flooring (or solid wood for that matter) must meet for resistance to denting or scratching.
In this case previewing realistic customer expectations would have gone a long way in diffusing the issues and educating the customer in prevention of the more obvious dents and scratches.
Another notable concern with engineered flooring is cracks in the face of boards. (Photo 5 and 6) This can be a very tricky issue to address. First, cracks in the face of flooring associated with checking, are inevitable to some extent. All wood will develop checks during the drying process. How many checks, and how severe in width and depth? It depends on the drying process and species involved. In addition, the manufacturing process for engineered flooring can create checks particularly with rotary peeled product when the curved wood sheet is flattened. Not only is there stress from bending it flat but the actual process of cutting the log with a knife fractures the wood. Even with sliced veneers the cutting action creates checks. These fractures and checks can become visible and, depending on the number and severity, become objectionable.
Most of the time the lay-out and engineering of the veneers help to keep the checks from becoming visible. The plies below the face restrict movement of the face and the checks move very little as conditions change and so are not visible. However, if the face moves at a different rate from the lower plies or the lower plies move differently from the face the checks/fractures can become visible. This can occur if the face veneer is at a higher moisture content than the lower plies. As the face shrinks to the condition of the lower plies, the lower plies resist the movement and the shrinkage occurs as space where the fractures or checks are. (Photo 7) Another influencing factor is the stretch of the finish that is put on the flooring. As the movement occurs and the small fractures open, some finishes are elastic enough to not fracture over the crack, while others fracture readily.
In order to avoid some of the movement the customer should be advised of the manufacturers’ recommendations for interior relative humidity which influences change in the moisture content of wood products. Some engineered flooring product directions require that the relative humidity be maintained in the home between 35% and 55% (some 40% to 60%, or 50% to 60%, or 30% to 50%) in order for the products to perform as expected. In areas where these required conditions require extra environmental controls, the consumer should be advised that associated mechanical equipment should be in place. However, in those cases where the face veneer and the lower plies were originally put together at different moisture contents, the face fractures/checking may be unavoidable. In many cases the flooring contractor is ultimately held accountable for installing in conditions where relative humidity did not conform to the required conditions.
Another issue that arises with engineered flooring is that of hollow spots and loose flooring or movement of the flooring. Occasional hollow sounding areas where there is no movement are considered acceptable in any glued down floor. Flooring that is placed on a slab that is not flat enough will not bond correctly to the humps and valleys and show movement associated with the unevenness. When movement is involved, the flooring edges can be stressed and over time begin to fail. This is an installation issue that proper prep work can take care of. Inadequate spread of the adhesive can also create hollow areas and movement which is also an installation issue.
The other condition associated with hollow areas is that of delamination of the flooring itself. (Photos 8 and 9) The glues that are used to assemble engineered flooring are very strong and are intended to maintain the integrity of the piece throughout its useful life. If not, similar materials like plywood sheathing would come into question after years in place. Delamination is normally associated with only the occasional piece, so the fix is to replace the defective piece. The HPVA ANSI Standard test for glue bond issues, calls for water soaking the flooring followed by drying up to 3 cycles and measuring the bondline separations. This procedure is an extreme and would not be a condition found at a home short of flooding the flooring. Daily environmental conditions associated with occupying a home will not approach the extremes of the ANSI bondline test, so delamination of flooring is not a site related issue or installation related short of actually putting the defective piece into the floor. Again the fix for defective pieces is to replace those pieces. Remember to advise the consumer the replaced board may be a slightly different color from the rest of the flooring as the in-place flooring has been exposed to different conditions. The difference in shading should gradually blend with the flooring over the length of time the flooring has been in place.
• Set proper customer expectations before installation.
• Don’t promise that the flooring won’t dent or scratch.
• The occasional face check/crack is an acceptable condition.
• The occasional hollow area is acceptable.
• A defective piece is just that, one that needs replacing.