As others have stated, Thompson's is bad news. I'm not sure what to recommend as an alternative, I have yet to find a retail product that works. Treated lumper needs to "season" a while before you try to seal it. I would suggest that you stay away from stain with high solids or paint. Use either one and you are committing to an annual ritual of pressure washing and refinishing. I used composite decking on the last deck I built, it looked good but it was more costly than treated lumber.

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