Treated lumber question

Has anyone found a way to tell the difference (in appearance or other clue) of treated deck lumber, that is, lumber designated for ground contact as opposed to lumber not for ground contact? At suppliers like Lowes the UC2 or UC4 designations are shown on the plastic barcode stapled to the wood somewhere, (you know they won’t last) but otherwise it would seem impossible to figure out…especially in the field. Thanks.

Ed Newman
Qual Tech Home Inspections LLC
Alamogordo, NM

No sure way of knowing that I know of.
The standard pressure treatment for most residential PT lumber is .25 retention and .4 for ground contact which is usually on the 4x4’s and 6x6’s at any lumber yard or box stores. The AWPA controls the markings and defines the standards.
So if know markings are visible, it would have to be assumed as .25 retention for above ground contact.

Test kits are available though for testing to see if it is CCA presure treatment. If the hangers are all rusted, it was probably ACQ treatment with the old G-90 hangers instead of the G-185 required.
There might be a test kit out there for that purpose, but fail to find one.

.28 :wink:

Bob, is that the Caliber or are you still using the CCA that you have stashed somewhere?;):slight_smile:

lol maybe im not up to date.

This was sent to any one have thoughts . Thanks … Roy

I was doing a digging into bluwood.
The main chemical is Disodium octaborate tetrahydrate which is used primarily used as an insecticide and herbicide.
I don’t think I would want to use this in my house.


With the CCA treated wood, any lumber treated at the higher levels for ground contact was usually incised to allow treatment to get farther into the wood and thus attain the higher density (lbs/cu ft) required treatment. The incisor marks are a serious of regular spaced little parallel slits.

Not what you want to make the picnic table out of either.:shock:

The basis of this is borax, your grandmother’s washing soda and generally considered harmless. Borax is recommended in “The Allergy Self-help Book” as a subsitute/replacement for Mr. Clean and all his stinky cousins!

I’m concerned with any other additives to the treatment whose formula has not been released as it is “proprietary”. Time will tell as this product has been in use for a while in the US.

Thanks. I think the series of slits for allowing deeper penetration of the preservatives is likely to be the best visual clue. again, thanks. Ed


Guys, think what you want, but do not be fooled by that statement on incisive perforations to obtain the .40 retention for Pressure treatment.

Be aware that all treated wood is not created equal. Most wood species do not readily accept chemical preservatives, and must first be “incised” or perforated with a series of small slits along the grain of the wood’s surface. Incising allows sufficient penetration of the preservative to meet American Wood Preserver’s Association (AWPA) Standards. Southern Pine is one of the few wood species that does not require incising.

Species and Products

Borates are used as a pressure treatment to preserve the following species per AWPA Standards:
• Lumber (without incising): Southern pine & ponderosa pine.

• Lumber (with incising): Coastal Douglas-fir, hem-fir and western SPF.

• Plywood: Southern pine and Douglas-fir.

Trees / logs from which commercial wood is cut have a number of different layers. The two primary layers are called heartwood and sapwood. Heartwood provides most of the “structural” strength to the living tree while the sapwood transports the sap from the base of the tree up to the leaves.

Wood preservatives penetrate sapwood easier than heartwood. As a result, wood species such as Southern Pine, which have a high percentage of sapwood, are predominately used in pressure treating.
Wood species such as Douglas Fir have more heartwood so modifications are typically required to the preservative to achieve adequate penetration and retention levels. The modification that is usually made is to change the “carrier” used in the preservatives. Often this carrier uses an ammonia base, which improves the penetration but also tends to increase the corrosivity of the preservative. (The carrier used to treat sapwood species usually has an amine base.) This increase in corrosivity may be short term or long term. Hybrid carriers, a mix of amine and ammonia bases, may also be used to treat heartwood species. Incising (perforating the wood with small slits) may also be utilized to increase the penetration of preservative in heartwood species.

Borate treated wood products can only be used for above ground interior or weather protected exterior applications. There are two retention levels. Each level is measured on the basis of either the boric oxide or disodium octaborate tetrahydrate (DOT).

• 0.17 pcf (B2O3)/0.25 pcf (DOT)

• 0.28 pcf (B2O3)/0.42 pcf (DOT) *

  • This higher retention is effective against the Formosan termite (Coptotermes formosanus).


ACQ can be used for any construction project and is particularly suited for applications such as decking, playgrounds, walkways, benches, outdoor tables and chairs, fencing, gazebos and landscaping, where long-term protection against decay and termites is a priority.

Hope this helps to clarify. :slight_smile:

Interesting about the Southern Yellow Pine (SYP). Conflict about Ponderosa Pine…in one place says it’s incised and another says not. Don’t have those species in my neck of the woods.

Here’s what’s being used in Canada now:

What projects can I use Alkaline Copper Quaternary (ACQ) or Copper Azole (CA) preserved wood on?

ACQ and CA preserved wood are registered for use in Canada by the Pest Management Regulatory Agency (PMRA) for the following uses: decks, patios, landscaping timbers, gazebos, residential fencing, walkways and boardwalks and freshwater docks.

Is CCA preserved wood still used?

CCA is registered for use in permanent wood foundations, agricultural applications such as farm fencing and posts, and industrial applications such as marine pilings, utility poles, bridge timbers and guard rail posts.

Lumber (without incising): Southern pine & ponderosa pine.

From: that you referred us to:

“Enhanced penetration in Douglas Fir, W. Hemlock and Ponderosa Pine”

This company claims that Red Pine does not need “enhanced penetration”.

My question is that do these companies really know which species need the enhanced penetration?