By Brett Miller, NWFA Vice President Technical Standards & Training
Even the most expertly installed wood floors can be adversely affected by poor finish application. The application of flooring finish is something that takes time, and practice, to perfect. Rushing this process, or performing it incorrectly, can lead to finish adhesion failure. These failures generally appear as either chipping/flaking finish, or peeling finish.
Chipping/Flaking Finish
Identification
The condition that occurs when a dried film of finish separates from the previously applied finish in the form of chips or flakes.
Causes
- Poor adhesion between coats.
- Surface contamination between coats.
- Not abrading or using too-fine of a grit abrasive between finish coats.
- Recoating a cured floor without proper preparation, either chemical or mechanical.
- Applying a subsequent coat of finish after the window to do so without abrasion (hot coating) has elapsed.
- Applying a less-elastic finish on top of a more-elastic one.
- More-elastic finish systems that stretch, rather than break, along board seams can weaken the adhesion between finish layers resulting in chipping/flaking.
- With some more-brittle/less-elastic finishes used in the factory-finishing process, a gain or loss in moisture and subsequent dimensional changes within the wood can result in finish chipping or shearing away from the wood.
- Sculpted, distressed, scraped, wire brushed, indented and scratched floors, or floors with over/underwood, may experience chipping or flaking away from the edges, corners or high points.
- Excessive finish on the edge of factory-finished flooring that prevents the flooring from being installed properly without damaging the finish. This also is known as cornicing.
- Rough handling of factory-finished flooring during installation.
- Site-applied or factory-applied UV coating cured improperly.
- Vertical deflection within the flooring system, typically board-to-board deflection.
- Poor adhesion over knots or sappy areas in the wood.
- Naturally occurring oils from various exotic wood species adversely affecting the drying process of the finish or sealer.
- Maintenance-related causes can include:
- Maintenance product used to clean the floor that is incompatible with the new coat of finish.
- Migration of contamination applied after the finish coats that may permeate the coating and destroy adhesion over time.
- Excessive moisture or steam being used during maintenance.
Cures
- If the chipping is isolated, spot repairs may be possible.
- Sand and refinish may be necessary to address widespread issues.
- For naturally occurring oils in exotic wood species, refer to the finish manufacturer for species-specific recommendations.
- With affected factory-finished floors, replacement of affected boards may be necessary.
- For maintenance-related issues, all causes must be addressed prior to any remedial action. Recoat, resand or replacement may be necessary dependent on the severity of the issues.
Peeling Finish
Identification
The condition that occurs when a dried film of finish separates from the underneath surface in the form of large pieces or sheets.
Causes
Finish-related:
- Surface contamination below finish.
- Poor adhesion between coats.
- Not abrading or using too-fine of a grit abrasive between finish coats.
- Recoating a cured floor without proper preparation, either chemical or mechanical.
- Applying a subsequent coat of finish after the window to do so without abrasion (hot coating) has elapsed.
- Applying a less-elastic finish on top of a more-elastic finish or paint.
- Applying a more-elastic finish on top of a less-elastic finish or paint.
- Finishes that are not compatible.
- Poor adhesion of a water-based finish system over oil-based stain, or previous coatings, that have not dried/cured sufficiently.
- Stain not sufficiently wiped up, multiple coats of stain applied or improper application of stain applied prior to subsequent coats of sealer or finish.
- Stain that is not suited for hardwood floor use, or that has been modified or tinted with a more-than-allowable amount of tint concentrate.
- Finish systems that stretch, rather than break, along board seams and edges can weaken the adhesion of finish or finish layers at board edges, resulting in adhesion failure.
- Poor adhesion over knots or sappy areas in the wood.
- Naturally occurring oils from various exotic wood species adversely affecting the adhesion of the finish or sealer.
- Improper tacking solvent used between coats.
Tape-related:
- The tape used on the finished floor was not recommended to be used on wood floors.
- The tape was adhered to the wood floor for a longer time than the tape manufacturerโs recommendation.
- Tape was applied to a newly coated wood floor finish.
- Plasticizers in the tape have created a stronger bond to the finish than the finish has to the previous coatings or the floor.
Factory-finished floor recoats:
- Improperly prepared surface prior to application of new coat of finish.
- Inadequate cleaning of floor surface prior to recoat.
- Lack of abrasion in bevels or other low elevation areas.
- Insufficient or incompatible finish and adhesion system selection (chemical or mechanical) used for the floor being recoated.
- Existing finishes incompatible with the new finish being applied such as:
- Perfluorooctane sulfonate (Teflon/Scotchgard) infused finishes that cannot be recoated.
- Waxed finished with urethanes or oils.
- Natural oils finished with incompatible urethanes.
Maintenance-related:
- Maintenance product used to clean the floor that is incompatible with the new coat of finish.
- Migration of contamination applied after the finish coats that may permeate the coating and destroy adhesion over time.
- Excessive moisture or steam being used during maintenance.
Cures
- If the peeling is isolated, spot repairs may be possible.
- Sand and refinish of affected areas may be necessary to address widespread issues.
- For maintenance related issues, all causes must be addressed prior to any remedial action. Recoat, resand or replacement may be necessary dependent on the severity of the issues.
- For incompatible finish systems, a resand is often necessary.
- For naturally occurring oils in exotic wood species, refer to the finish manufacturer for species-specific recommendations.
- If tape is used during painting procedures, only use a tape specifically recommended for wood flooring. Place the tape extremely carefully on the finished floor just prior to the painting process, and only after applied finish has cured completely. Immediately remove the tape by carefully pulling it against itself at a 45ห angle upon application of the paint. Do not leave the tape on any longer than needed to apply each coat of paint.
The National Wood Flooring Association has detailed information about finish adhesion failures available through NWFA University, an online training platform that is convenient and affordable. More information is available at nwfa.org/nwfa-university.aspx.
