How To Choose Pressure Treated Wood

Build beautiful outdoor projects with bug- and rot-resistant pressure treated wood

Keep wooden outdoor structures beautiful for years by building with wood treated to resist termites and fungal decay. This guide will walk you through the types and benefits of pressure-treated (PT) wood.

Safety: Always wear gloves, eye protection and a dust mask (NIOSH N95) when handling wood. Due to preservatives in pressure treated wood, it should never be burned. Sawdust and scraps should be disposed of in a landfill.

What Is Pressure Treating?

Pressure treating is a preservative process that helps wood withstand the elements and wards off termites, microorganisms and fungal decay.

The most common chemicals used to treat wood are Alkaline Copper Quaternary (ACQ), Copper Azole (CA), and Micronized Copper Azole (MCA).

Recent changes in the US treating standards now require Ground-Contact treated wood for most end use applications, which has two times the preservative level as Above-Ground treated wood products. Ground-Contact treated wood is available at The Home Depot in most of our dimensional lumber and timber products. 

Ground-Contact treated wood provides long-term protection against termite and fungal decay attack and can be used in most outdoor applications. 

During the pressure-treating process, the wood preservatives are forced deep into the wood. The treating solution consists mostly of water. Because the treated wood absorbs a significant amount of water, depending on your location, it may take several weeks for the wood to dry. During this period, some shrinkage and warping may occur. 

If you desire to paint or stain the treated wood project, it is important that the wood 
be dry enough to accept a coating. The best way to determine if the wood is sufficiently dry to paint or stain is to sprinkle droplets of water onto the wood. If the water droplets are absorbed, the wood is ready to be painted or stained. If the water droplets bead on the surface of the wood, it is too wet. You should wait a few days before attempting to paint and stain the wood. We have a broad selection of stain and paint products specifically formulated for treated wood. 

Pressure-treated lumber can last 20 years or more, and most pressure treated wood comes with a residential and agricultural limited warranty.

Pressure Treating



ACQ/CA vs. MCA Pressure Treated Wood

See details on the two primary types of pressure treated wood in the following chart.


ACQ/CA (Copper Azole) and Pressure Treated Wood MCA (Microionized) and Pressure Treated Wood

Preservative Components

Primary biocide = copper amine


Secondary biocide = quat for ACQ/azole for CA
  

Primary biocide = 
microionized copper

Secondary Biocide = Azole

Building Code Compliance

Yes, via AWPA or NER-628
(ACQ or ESR-1721(CA)    

Yes via International Code Council
ESR-2240 and ESR-1721    

Warranty

Lifetime Limited Warranty

Lifetime Limited Warranty

Protects Against

Fungal decay and termites

Fungal decay and termites

Aluminum Compatability

No

Yes

Fasteners Recommendation

Hot-dipped galvanized
(G-185) or better

Hot-dipped galvanized
(G-185) or better

Color

Darker Green in color when first purchased

Light natural color when first
purchased

In general, microionized PT wood
is drier and may be stained or
water sealed sooner than ACQ/CA PT wood. Due to its natural color, it stains to a truer color than ACQ/CA PT wood.