One yr. old pressure treated wood pergola turning green
I have a one year old non finished pressure treated wood pine pergola (no floor) that needs to be stained here in Ohio. Since we power washed it a month ago, 2 of the vertical posts have turned darker brown and green on the entire east side and the other 2 posts are doing the same on the west or south side (east side gets 3/4 day full sun).
The green does not look like mold what is causing it? The wood is not gray but is turning brown. Do we need to use a deck cleaner to restore the wood before staining?
I've tested 3 semi-transparent water base acrylic stain colors, one is darker "brick red" similar to cedar red, the other a lighter yellow orangish tone that gives the aging wood a pleasing warm look whether it is over the greenish part or not.
If the treatment contained copper, when you pressure washed you probably accelerated the oxidation. As you know copper develops a natural green patina over time. I guess it could be moss spores trying to establish themselves depending on where you are. Unlikely since you say the east side which is turning green is in full sun.
If the pergola has been sitting a year without staining, I would clean it so you know you have a good starting point. Then if you found a semi-transparent stain that looks nice go for it. You can always step up to a semi-solid or even a solid if you find dramatic discoloration. It sounds from your sample things will be just find.
Please do not tell us you are using Behr?
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