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How to Remove Gray Discoloration from Lumber

Posted 21 May 2021 1:28 PM by Jase DeBoer

Your wood deck, fence or patio may have looked pristine upon installation, but within a few years, it likely started to change color. We all want our investments to last for decades, and with these few tips you can restore your outdoor wooden structures in a weekend.

Why Does Discoloration Occur?

Many wood species experience discoloration. With constant exposure to water, sun, dirt and other elements, lumber will naturally fade to a gray tone if not treated and coated with a waterproof sealer. Sealers also lose effectiveness over time; without annual to biannual sealing, your lumber will likely fade. Additionally, mold and algae can cause discoloration to your surfaces. Naturally occurring organic materials are difficult to avoid but easy to remove with a bit of elbow grease.

Prevent Future Discoloration

Most discoloration can be removed with cleaning. We recommend using a pressure washer to begin the process. Spray the wood with a fan-tipped nozzle at the lowest setting. Be sure to spray no less than 12” away from the surface while working in a sweeping motion. You may need to make multiple passes with your pressure washer before removing the discoloration.

For stubborn algae and mildew stains, an all-purpose deck and home cleaner can be applied. Scrub the cleaner into the wood and rinse as suggested. Always follow the instructions of the cleaning agent and wear appropriate skin and eye protection.

For particularly rough and discolored areas, a sander may be used. Start sanding with a medium- grit sandpaper. Finish your sanding with a finer-grit sandpaper for a smooth finish.

Restore Your Lumber

Once your surface is clean and completely dry, you may stain your wood, if desired. First, be sure to test if your surface is ready for stain. Once completely dry, drip water onto the surface. If the water penetrates, your wood is ready for stain. If it beads, there is still a remaining layer of waterproof sealer. A wood stripper would be necessary before applying new stain. Once the stain is dry, apply a waterproofing sealer to lock in your color.

If you would like to avoid staining altogether, consider building with color-treated lumber. Color is infused into the wood, eliminating the chore of staining. Simply seal every year or two for color that lasts.

A side-by-side comparison of a real cedar panel (left) and a ProWood Color Treated panel (right) after two years of outdoor exposure
A side-by-side comparison of a real cedar panel (left) and a ProWood Color Treated panel (right) after two years of outdoor exposure

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