Evolution Of Pressure Treated Decking

Do You Know You Have Choices?

This quaint little wood deck was made entirely of pressure treated wood and is among the most affordable options for many homeowners.

It's true. The pressure treated decking market has changed a lot the last ten years and continues to see new solutions.

Since at least 1940, CCA was the preservation standard for outdoor wood. Then in 2004 the industry moved to phase out CCA (chromated copper arsenate).

Goodbye CCA, Hello ACQ

But concerns of leaching and human exposure to arsenic in residential environments caused a major change.

Everybody switched over to ACQ (alkaline copper quaternary) which was safer but caused corrosion of many standard metal fasteners and connectors.

It can still leach out but the arsenic has been removed so it's no longer the same worry.

But this change led to people paying more so use stainless steel hardware or heavier zinc coatings to avoid that problem. ACQ leaves a very deep green tone to the wood which is unmistakeable.

And Now, There Are More Options

There are two new and exciting pressure treating options for decking boards. MCA (micronized copper azole) and Thermal Treating are solutions to ACQ


Pressure treated lumber from the MCA process has a number of improvements.

Firstly, it's not so noticeabley green. Lumber treated this way is only slightly darker which is a nice cosmetic benefit. A much more natural look to the decking.

The copper used in this process is much smaller and also water soluble. This means the copper preserving particles can penetrate much deeper into the wood rather than sit on the surface.

Deeper penetration also means far small chance of it leaching out.

But what is really great is you can use regular galvanized hardware and connectors. You don't need extra zinc coating or more expensive stainless steel.

So look for this on the market. Here is one place you can find it.

Thermal Treating

Common ACQ treated framing lumber

This is a very promising new way to make pressure treated decking.

The concept is to heat the wood and kill all the sugars in the wood that bugs and bacteria love to feed on.

No food. No decay. That's the theory.

But it's a three stage process and various temperatures that uses a fair amount of energy to do and so that raises the cost of the treated decking boards to about the price of the higher end composite decking.

It is positioned in the market as a higher end decking material and for good reason.

The boards don't absorb water because one of the chemicals needed for water to adhere to is removed. This keeps the treated decking boards very stable. Twenty five year warranties are offered by this company.

Pressure Treated Lumber Is Still The Most Common

That's the latest and greatest on pressure treated decking processes. Three are chemical additives and the fourth is non-additive but uses more energy.

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