How to Seal Treated Wood
Pressure-treating only prevents wood from rotting, insect infestation and mildew---it doesn't stop the natural weathering processes that leach protective oils out of the surface of the wood. Pressure-treated wood, left unsealed, will weather and turn gray, crack, check, and warp. According to AskTheBuilder.com, another common misconception is that pressure-treated wood shouldn't be touched until it has "seasoned" outdoors for at least a few months. While pressure-treated lumber shouldn't be painted until it has seasoned, all pressure-treated wood should be sealed immediately after it is purchased. Does this Spark an idea?
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Things You'll Need
- Pressure-treated lumber
- Wood brightener (optional)
- Wood sealer
- Brush or roller
- Roller pan
- Drop cloths
- Detergent
- Brightener
- Pail
- Water
- Sponge or cleaning brush
Instructions
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Cleaning and Sealing
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1
Clean the wood. Immediately after buying the wood, clean it. This might amount to nothing more than just brushing off loose dirt. If it has worse problems, use detergent and a sponge or brush to clean off stubborn stains and dirt. Rinse well and let the lumber dry.
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2
Brighten the wood. Commercial wood brighteners are used to remove dark stains and give a more uniform color to the wood. This step is not necessary if there are no condition problems with the wood or if it is going to be painted. Wood brighteners are water-based, wood-bleaching products. Follow specific manufacturer's instructions for use. Wood brighteners are the same as deck restorers or deck cleaning solutions---just make sure the product you choose is for pressure-treated lumber.
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3
Choose a wood sealer. There are water-based sealers and oil-based sealers. Water-based sealers are used when the final finish for the wood is going to be flat or matte. Use an oil-based sealer if you want a glossy finish. Some oil-based sealers double as a primer coat if you want to eventually paint the pressure-treated wood. Choose the right sealer with the end project in mind and it will save you time and a lot of effort.
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4
Let the treated wood dry and check the weather. Don't apply sealer if the wood is wet or if it is going to rain the same day. Most sealers (even oil-based) will lift off the wood if rained on within a few hours of application. Check the instructions that come with the sealer to know how long the wood has to remain dry after applying the sealer.
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5
Apply the sealer. Use drop cloths to catch any excess---the liquid sealer may be toxic to plants and pets. Use a roller or pad to apply to flat surfaces, and use a brush to soak sealer into the end grain. It is very important to seal the end grain: This is where preservative will wick out of the wood, and where water and rot will seep in.
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Follow the sealer manufacturer's instructions for drying time before applying stain, paint, or a clear finish coat.
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Tips & Warnings
The sooner you apply the sealer, the less work you have to do to get uniform color and protection. Even stacking lumber in sunlight will cause uneven discoloration. For sun-exposed projects like decks, consider sealers and finishes with UV protection. Wolmanized lumber is another name for pressure-treated wood. Use the same sealing procedure no matter how it is named.
According to the U.S. Environmental Protection Agency (EPA), most treated wood made from the 1970s up to 2003 contains arsenic preservatives (chromated copper arsenic, or CCA). This type of treated wood should be sealed to prevent leaching toxic arsenic into your yard. Treated wood should never be used indoors.
