The finish separates from the wood flooring or from existing layers of finish. The finish peels away in sheets or strips.
Delamination of finished can be caused by a variety of non-related causes. It is usually caused by one rather than a combination of these causes.
Some surface contaminants such as oils or waxes from previous finishes, or body fat associated with sports floor use may not be completely removed by sanding. It is believed that heat generated during sanding causes expansion of oils and leads to a reduction in the viscosity (thinning) of the contaminant which enables the contaminant to further penetrate the wood fibres. See solutions.
First establish if the finish is delaminating from the bare wood or from previous coats of finish. Check for signs of abrasion that may indicate that unreasonable wear may be contributing to the problem. Occasionally surface contaminants such as oil can be seen or felt on the bare wood surface or between coats of finish. Adhesion of coatings including wood finishes can be tested with a pull off adhesion tester conforming to ISO 4624, ASTM D4541
In many case where finishes have delaminated it is necessary to re-sand and seal the whole floor. Where the defect is limited to a small area, localised sanding and refinishing can produce satisfactory results.
Where finish is delaminating due to suspected surface contaminant such as oil or wax, the floor can be thoroughly re-sanded, a primer barrier seal can be used to create a barrier before application of the surface finish to aid adhesion.
Where body fat is suspected (on sports floors etc.) to be the cause of poor adhesion, following re-sanding, the wood surface can be cleaned using a washer-scrubber-dryer and purpose made body fat neutraliser, before application of a new finish.
When using ethanol based primers, be aware that these can cause edge bonding which can lead to rafting. As such these are less well suited to large floors, and where there will remain gaps between boards at time of finishing. Furthermore the rapid drying of ethanol based primer barrier seals make them less well suited to large floor areas, as this can lead to overlap streaks.
An alternative to using a lacquered finish is to use an oil or wax finish which are less likely to be affected by oil based surface contaminants.
Whatever method of remedial action is used, always try a suitable test area before commencement.