Can Pressure-Treated Lumber Be Exposed to Freshwater or Saltwater?

In this episode of our treated lumber series Dennis McWhirter of Exterior Wood explains when and how pressure-treated lumber can be exposed to freshwater and saltwater.

Jim Coshow

 


Treated lumber is a popular building material that plays a key role in the construction of many structures in the Pacific Northwest. Our good friend, Dennis McWhirter of Exterior Wood, is an expert on pressure-treated wood, with nearly three decades of experience in the industry. In this series, Dennis provides answers to some common questions and reminds us why treating lumber is one of the best things we can do to help preserve our greatest renewable resource.

In today’s episode, Dennis answers a common question: Can you expose treated lumber to freshwater or saltwater?

Can treated lumber be submerged in freshwater or exposed to saltwater?

Yes, but the conditions are important. When submerging in freshwater or exposing to saltwater splash, lumber should be treated with 0.15 or 0.31 pounds of chemical treatment (per cubic foot of wood) in order for the wood to maintain its integrity. To be submerged in saltwater, lumber would need to be treated with 2.5 pounds (per cubic foot of wood) of our chemicals. Material for these applications is typically sourced through other industrial treatment providers.

exposing water to treated lumber

What’s a scenario where using treated lumber near water is advised?

Building docks, piers, and other marine structures are all cases wherein natural lumber won’t hold up over time. In cases where the wood will be exposed to salt spray (i.e. atop pontoons to create dock surfaces), Dennis advises using lumber treated with at least 0.15 pounds of chemical per cubic foot of wood.

treated lumber water

We hope this video helps you understand more about pressure-treated lumber so you can decide on the best materials for your next project. For more on treated lumber, check out how pressure-treated lumber is made, a history of the chemicals used in treated lumber, and how pressure-treated lumber reacts to metal. And stay tuned for the rest of the series as Dennis answers more questions about pressure-treated wood and its uses.