Engineered wood flooring is constructed of multiple layers of wood in a manner very similar to plywood. It ranges from three to 10 layers thick, with the wood grain running in the opposite direction in each successive layer to create dimensional stability. The top layer is the finished hardwood, while the sub layers are birch or pine. These species provide the stability necessary, but are cheaper to use in manufacturing the product. All of these layers are glued together and sanded, and then the stain and multiple coats of finish are applied. Delamination issues usually occur when the wood gets wet and debases the adhesive, or when a manufacturing issue causes glue failure.
Determine and fix the cause of the delamination. If it's a water leak, repair the leak and then let the wood dry completely before attempting to fix the floor. Occasionally, just the top layer detaches and some carpenter's adhesive can be used to glue it back down. Unfortunately, delamination usually affects multiple layers. In such cases, the affected flooring should be removed.
Tape off the unaffected area surrounding the repair so that it doesn't get scratched during the removal process. Use painter's tape so that it doesn't leave a residue, and apply a double layer so the saw guard or chisel doesn't scratch the floor while you are working.
Use a piece of the flooring itself, or a tape measure, to set the circular saw blade depth to the thickness of your flooring. Make two parallel cuts at least 1 inch from each edge, down the middle of the board you want to remove. Go as close to the end joints on both sides as you safely can without hitting the undamaged flooring. Now make a diagonal cut through the middle that crosses both of your earlier cuts.
Use a chisel to finish the last bit that the saw couldn't reach on the ends, and then lift the centre pieces out prying from your cross cut in the middle of the board. If you flooring is nailed down, this will easy, but if it is glued, you must be patient and mindful of the existing flooring. Once the centre piece is out, you must then chisel out the two side pieces by pushing them toward the hole you cut out of the middle.
Scrape the subfloor clean, removing any traces of the damaged wood and adhesive if necessary. Be certain to clean out the grooves and underneath the tongues of the undamaged wood remaining, and vacuum out the repair area.
Cut the new pieces to fit, and then lay them in without glue to check that they go in properly. Spread the glue over the clean sub-flooring, and then place the new wood in the adhesive. Remove the underside of the groove or the tongue where necessary to get it to go in. These can be taken off with a chisel, or by running the pieces through a table saw, if you have one.
Wipe up any excess adhesive on top of the floor, and then put some weight on the repair area. Leave it overnight until the glue completely hardens.
Don't place too much adhesive near the joints, or it can squeeze up through the cracks. Even if your floor originally was nailed down, use adhesive for the replacement boards so that you don't have to nail through the top of the wood. Top nailing makes the repair more noticeable.
Use a new blade on the saw and hold it firmly. The blade can catch, and dangerously jerk the saw if you are not careful.