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 digs into how to preserve the longevity of your pressure-treated wood—and take advantage of its lifetime warranty. 

How to Maintain the Lifetime Warranty of Pressure-Treated Lumber

What are the best practices for maintaining the warranty of my treated lumber?

Our pressure-treated wood has a lifetime warranty—but you’re only eligible if you treat the product correctly. When you’re out in the field working on a deck, you probably plan to seal it all at once when you’re finished. But prior to that, you’re likely cutting treated joists and beams to place them. 

When you make those cuts to pressure-treated wood, you break the sealed envelope on that end—exposing it to dirt and water. Those two elements together make the perfect habitat for fungus, and fungus causes wood to rot. The pressure treatment on wood only penetrates 4/10 of an inch, so if you cut off the top of a four-by-four-inch post, you’re exposing 2½ inches of wood without any chemicals on it. 

If you don’t seal that cut end out in the field, you actually void our lifetime warranty for that piece of lumber. I’ve been out on numerous deck claims, and you can tell which ends have been sealed or not, even after 10, 15, or 20 years—just by the difference in coloration. 

The only requirement for the warranty is to make sure any ends cut out in the field are treated with a sealant. We have a product called end-cut solution that we recommend people use when cutting pressure-treated wood. 

pressure treated lumber

What if I’m working with a contractor?

Typically, the warranty is to the original owner of the pressure-treated lumber—unless you’re working with a contractor. So let’s say a contractor comes in to buy some treated wood then takes it out to a job site and builds a deck for their client. In that case, the warranty is transferable from the contractor to the homeowner. 

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 this breakdown of how metal affects pressure-treated lumber, this post outlining the difference between Professional and Premium-grade lumber, and a history of pressure-treated wood’s chemical composition. And be sure to stay tuned for the rest of our series with Dennis.