Not all treated southern yellow pine has clear vertical grain like this, of course, but your PT decking will look better if you run it lightly through a power planer to remove grade marks prior to installation.
John Paulin Not all treated southern yellow pine has clear vertical grain like this, of course, but your PT decking will look better if you run it lightly through a power planer to remove grade marks prior to installation.

Q: What’s the easiest way to remove grade stamps and other markings from PT lumber? My clients haven’t decided yet on whether they want a clear or semi-transparent stain, but they don’t want letters and numbers showing through the stain. Is there a cleaner or a special technique for removing these tenacious markings?

A: John Paulin, of Tailor Decks, in Statham, Ga., responds: While the water-based ink that’s used for marking pressure-treated lumber should eventually disappear with exposure to weather and foot traffic, I have never had a customer who liked the look of grade stamps and pencil marks all over his or her new deck. I’ve tried to remove them prior to staining by power-washing, and I’ve tried scrubbing them away with detergent and a scouring pad, too, but with limited success. I’ve also tried sanding boards after installation with a 3-inch by 24-inch belt sander and 80-grit paper. Sanding can work, but sometimes the ink penetrates the wood fairly deeply and is difficult to remove, and sometimes PT decking is so wet that it clogs up the paper. In addition, you have to be careful not to sand the heads of the nails or screws in the installed decking. Sanding belts are expensive, too.

Now I run all of my deck boards through a power planer prior to installation, skimming off the least amount possible. If a planer isn't available, or if the decking is crowned, a hand planer can be used, though you might need to clean up the boards a bit afterward with a belt sander to remove the planer marks. While this process sounds tedious, it’s actually not too bad once you get set up. As long as you clear this step with your building inspector, taking a little extra time to remove the marks prior to installation saves a lot of time later on, and significantly improves the appearance of PT decking.