When your dog has an accident and urinates on a wood floor, it is fairly easy to clean up the area if you discover it before it soaks into the flooring. If it's undiscovered for a prolonged time, dog urine will gradually soak into the floor, reacting with the varnish, paint or other coating to leave a dark stain. Very old stains take more effort to clean up. In some severe cases, the flooring in the area of the stain may need to be replaced.
Remove any rug that is on top of the hardwood flooring. Clean the rug as you normally would, in keeping with manufacturer instructions for the type of material the rug is made from.
Press paper towels into the urine puddle on the hardwood surface to blot up all of the moisture, then pick them up. Do not wipe the floor with the paper towels.
Pour white vinegar on the stain and allow it to sit for about two minutes. Work the vinegar in to the area with a soft brush. Blot up the moisture with paper towels.
Sprinkle pet stain neutralizing powder on the urine spot. Allow the powder to remain in place for a time, following the package directions. Vacuum the powder from the wood floor.
Wrap a piece of 240-grit, very fine sandpaper around a sanding block. Sand the stained area of the wood floor. Press the sandpaper gently against the area, and use a circular motion to remove a light area of the stain or sealant from the floor.
Wipe the sanding debris from the floor with a soft cloth. Examine the area to see if the urine stain is still evident. Continue sanding until you no longer see the stain.
Dip a paintbrush into a shellac-based primer, and brush a light coat of the primer onto the sanded floor area. Allow the primer to dry until it is no longer tacky to the touch.
Brush a coat of flooring stain or polyurethane on top of the primer. Match the brand and color that is on your flooring. Allow the new coat to dry completely before you walk on the area.