Do You Need to Seal a Pressure-Treated Deck?

Pressure-treated wood still needs to be sealed and protected for best results.

One of the only downsides to building a deck out of wood is that in comparison to stone and brick surfaces there is a limited lifespan. Although untreated wood will weather and suffer damage from weather in a span of only 10 years or so, pressure-treated wood that is infused with preservatives can last for more than 20 years. Taking the time to seal it will help it last even longer.

Normal Wood

Traditional wood that is used for any type of construction will eventually break down due to Mother Nature. Exposed wood in an exterior setting wears out far more quickly due to the sun, insects, water, freezing and thawing and the entire combination of natural elements. The color will fade, sections can rot due to overexposure to water and insects can eat the structural integrity out of wood, which is why pressure-treated wood is preferred for outdoor deck projects.

Pressure-Treated Wood

Designed to withstand the power of nature, pressure-treated wood is lumber that has been cut down to size and then placed inside of a pressurized chamber that is filled with preservatives. These preservatives are pressurized deep into the wood itself, and the wood can then be used for outdoor decks. The combination of preservatives helps the wood last against water damage and other natural wear and tear, but it does not make the wood impervious.

Cleaning

One of the downsides to wood is that every time you clean the decking, it wears out the surface of the wood. As wood breaks down, the fibers become soft and dead, and they coat the surface of the wood. When they are cleaned, they reveal an exposed layer of new wood underneath. Eventually, you will reach a point that the preservatives have not reached, which is why sealers are still important even with pressure-treated decks.

Maintenance

Regular sealing is essential for any deck, regardless of whether you are using pressure-treated wood. The important thing to remember is that you should use only sealers that are specifically designed for pressure-treated wood, as general sealers will have a hard time penetrating and working with the preservative. Special sealers designed for this type of wood will help it last the longest.

Resources

• This Old House: Wood Decking Materials
• Ask the Builder: Treated Lumber