The difference between treated and untreated lumber

Pressure Treated Lumber

Nails or screws, rebar or expanded lathing, treated or untreated - the decisions we make on a daily basis for the projects we're working on make a big difference in how well those projects will hold up over time. But how do you decide whether your project needs pressure-treated or untreated lumber? Here's our guide on when to go treated and when to keep it plain:>

What is pressure treated?

Pressure treatment of softwood dimensional lumber goes way beyond the fact that it can be a bear to cut and feels as heavy as iron when  you're hauling it into a job site. But beyond the everyday issues, what makes pressure treated lumber different than regular lumber? Resistance.

Hardwood floor being sanded down with power sanderPressure treated lumber has chemicals forced into it by placing the lumber into a vacuum chamber and then introducing a preservative that is forced deep into the wood. The preservative repels insects and help prevent rot. If you've ever had to repair a frame structure that stayed wet for a while, you've had to deal with rot or insect issues and can see the advantage of using a wood that doesn't have these issues.

At one point, pressure treated lumber was taken off the market due to the prevalence of arsenic in the preservative compound, but the preservatives used today are less toxic. But before you build new raised beds for your vegetables or a new swingset for your kids, let's take a look at where it's okay and where it's not okay to use pressure treated lumber.

Where to use pressure treated lumber

Pressure treated wood was designed for contact with the ground or in areas where insect activity is particular problematic. When you're considering using pressure treated lumber where children or food may come into contact with it, you'll want to review the label that's attached to pressure treated lumber products today.

Depending on the compound used, you may want to limit where you use it, but most modern pressure treated lumber contains copper-based compounds such as ammoniacal copper quaternary (ACQ) or ammoniacal copper quaternary (ACQ), in addition to some boron-based preservatives. ACQ has been noted to corrode galvanized steel hardware more quickly than others and can also cause issues with aluminum hardware, so you'll want to stick with stainless steel or hot-dipped galvanized hardware.

Other alternatives to pressure treatment

But what if you need that level of protection for your project, but don't want to risk exposing your family to anything that is used in the pressure treatment process? There are a few alternatives available, which we'll detail here.

Red CedarOne way of getting around the inherent issues of pressure treated lumber is to use woods that are naturally resistant to rot and insect damage. Redwood and red cedar are both excellent choices, with natural resistance to the issues that plague other wood species. 

Another option is plain oil-based exterior-grade paint. If the wood will be in contact with the ground, you'll want to pre-paint the ends in contact with the earth using an enamel that will stand up against contact with the ground so that the water won't crack and allow water and insects into the wood.

If you'd prefer a more natural option yet, you can look at using whitewash to "paint" the exterior of the structure. A combination of lime and water, whitewash was used for centuries and essentially creates a calcium carbonate shell on the outside of the wood. Whitewash should be repeated on at least an annual basis, requires gloves as it can be drying or caustic to the skin and won't hold up well on the part of the wood that is in contact with the ground. You can adjust the color using a variety of natural pigments.

Now that you've had the opportunity to explore the options available to you for untreated, pressure treated and alternative treatments for your projects, it's time to go to work. Contact us for a quote or schedule a delivery from one of our five four-state locations.

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Photo credit: US Fish and Wildlife Service - Recovery Act Team / Foter / CC BY
Photo credit:
Carlin Joe / Foter / CC BY


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Wallboard Supply Company is a third generation, family run business that has been serving New England's building needs since 1970. Bob Filion started the company with a commitment to provide quality drywall and finishing products with unmatched customer service. The company has grown over the years, expanding its' product range, but never wavering from its' core values.