How do I stop knots from bleeding/bleaching my deck?

Answered by Jeffrey ~ April 30, 2010 ~ Comments

Every year I stain my deck. Within a few months, the knots begin to bleed through and become a powdery, white substance that runs several inches/feet from the original knot. There are dozens of these and they are unsightly. I have been told there is nothing I can do but paint the deck. I want to continue to stain it. Is painting really my only option?

Paul H. ~ Raleigh, North Carolina

Jeffrey Anderson

Hi Paul, Sealing knots under stain can be difficult because most of the products used to seal knots can tint the area where it is applied over the knot, and it can end up being a different shade after the stain is applied.

Knots can take years and years to dry unless they are sealed, and the humidity of Raleigh, North Carolina doesn't help. The easiest solution would be to do what has been suggested; paint the deck. But even with painting the deck you will need to seal the knots or you will be repainting it every year when the knots bleed through.

If you do want to keep is as a stained deck though, I would give a product a try. There is a company named Zinsser, their website is www.zinsser.com, and they have an extensive line of interior and exterior sealants. I don't know what color your stain is, but it looks like they have some exterior sealants that are clear or very lightly tinted. They do not sell through their website, you will need to find a local distributor, but you might contact them and tell them what color of stain you are using, and they can suggest which of their products would work the best. You might also try using a shellac over the knots, it is available in a clear finish, and might seal the knots and eliminate the bleed through.

Whatever product you decide to try, I would use it in a very small inconspicuous area first, re-stain over that area, and let it sit for a couple of days to see how it turns out. It is easier to redo a small section of your deck than having to redo an entire area.

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