Damp mopping causing dark spots?

Q: I have customer — we clean their house every week. Part of our process is to damp mop the hardwood floors throughout the home. We use a mild peroxide based cleaner that is diluted according to manufacturers directions for the damp mop (EcoLab). Recently three dark spots appeared on the floors, blackish and about 12 inches in diameter. One has a sharp side about two inches running parallel to the carpet.

The owner thinks we left too much water on the floors and it caused these spots. I sent pics to a local hardwood floor company and they said it looked like dog pee — I ordered a blacklight. The owner is sure their dog didn’t do this and that we put too much water on the floor. The owner said he talked to friends who work in the flooring business and they are certain that it was caused by water damage. BTW it has also been raining here off and on for a month in NC. If the black light shows markings then I will discuss the uric acid issue – but if not, what should be my next step to assess this?

A: Is there a basement under this room or just a crawl space? For your own benefit I would suggest using a floor cleaner manufactured by either wood floor manufacturers or floor finish manufacturers. You can spray mist a section of the floor and then wipe over it with a dry cloth or micro weave or terry cloth mop. This cleaners evaporate quickly. Companies that make such cleaners include Poloplaz, Basic Coatings and Bona Kemi. Leaving any amount of liquid on a wood surface long enough is bound to create a water stain. My guess, given the marks as you describe, sure sounds like pet stains. I’m not sure what to suggest. A pet who normally never goes in the house can suddenly change for several reasons, two of which would be health issues and emotional upset. Have you ever noticed wet areas when first entering this home because this sounds like it has been repeated more than once in the same spot.

Follow-up Q: I haven’t noticed wet areas. There is a basement under the house although I’m not sure if it spans under the affected areas. We have cleaned this house 3 times and we use microfiber cloths that have been rung out. Even if the were not fully rung out it is hard for me to envision that they would leave enough water behind. The pet is in the house but the owner says there was never a problem before. We also have had more rain in the last month than I recall. I Will send you some pics of the spots. Thank you for responding.

A: Why these significant black spots in a few spots, because it seems to indicate standing moisture of significant amount..

Follow-up Q: The other question I guess I have is if I want to get an unbiased expert opinion on this , someone I could pay to come out. Would a building inspector be the right person? Or someone from a flooring company? It seems that in order to fix a spot you need to know what the root cause is. Where would one go to get someone who would take an educated scientific approach to figuring this out?

A: Contact the National Wood Flooring Association. They do have certified inspectors. If you go this route, I’d be interested to know what his conclusions are. Thanks.

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