Dark Stains On Deck - Not mold

by James
(Portland, Oregon)

I own a carpet cleaning business. I cleaned this house about a week ago and today I received an email saying that I put theses stains on her deck. Not sure how this could happen. Maybe I had something leaking. Do you know how this could be fix?

Editor's Comments

One of the most mysterious kinds of dark stains that can appear on wood is caused when iron shavings or filings fall on to wood. Moisture soon causes a reaction either with the tanins in the wood as is the case with cedar and or rust occurs leaving a stain in the wood.

What you have hear however does not seem to be like metal filings. It appears like a liquid was dribbled or dropped onto the wood. It is anyone's guess what this might be.

If you are in the carpet cleaning business you will know the kinds of chemicals used for cleaning and that might be your first starting point for research.

The challenge here, and this applies whether it is a chemical stain or the metal filings and rust scenario above is that removing it is not a simple task. It can get even more challenging if it has absorbed deeply into the wood.

In such cases, the only way to fix the problem is to sand away the surface to reach fresh unstained wood. But if the stain is too deep this may be impractical. Then you would be looking at applying a dark stain or removing boards or learning to live with it.

If there is any visitor who can identify or help our reader out please leave a comment.