For Larger Minds than Mine

[JRD]

Just started wondering and no one I've asked in conversation has been able to provide a good answer.

Thus, I toss it out to larger minds than mine.

Why are treated 4x4's that off green color, when treated decking boards are not? I assume the same
non-arsenic based treatment is used, or if not that could account for the difference in color.

Anyone with the answer?

Thanks,

Jim

 

[Mike Davis]

Most of the treated wood that’s two inches or less in thickness tends to be treated for above-ground use. Since less chemical or a different chemical is used it may react with the wood differently causing a different color.

Which wood preservative systems are standardized by AWPA?
In today's marketplace, there are many wood preservative systems available to the public. It is important that those wood preservatives reviewed by AWPA's Technical Committees and found in AWPA Standard U1 are selected at retentions that are appropriate for each Use Category. The following table is specific to Southern pine and Douglas-fir, but should be helpful in determining if the treated wood at your local retailer is treated with the correct preservative at the proper retention (expressed in pounds active ingredient per cubic foot of wood):​

​

​

Code	Preservative Name	UC1, 2	UC3B	UC4A	UC4B
ACC	Acid Copper Chromate	0.25	0.25	0.50	---
ACQ	Alkaline Copper Quaternary (Type B or C)	0.25	0.25	0.40	0.60
ACQ	Alkaline Copper Quaternary (Type A or D)	0.15	0.15	0.40	0.60
ACZA	Ammoniacal Copper Zinc Arsenate	0.25	0.25	0.40	0.60
CA-B	Copper Azole, Type B	0.10	0.10	0.21	0.31
CA-C	Copper Azole, Type C	0.060	0.060	0.15	0.31
CuN-W	Waterborne Copper Naphthenate	0.070	0.070	0.11	---
CX-A	Copper HDO	0.206	0.206	---	---
EL2	DCOI-Imidicloprid-Stabilizer	0.019	0.019	---	---
PTI	Propiconazole-Tebuconazole-Imidicloprid	0.013	0.018	---	---
PTI	PTI plus Stabilizer	0.013	0.013	---	---
SBX	Inorganic Boron (Formosan termites)	0.28	---	---	---
SBX	Inorganic Boron (non-Formosan termites)	0.17	---	---	---
	What do the AWPA Use Category designations mean? The Use Categories are a shorthand method of describing the various hazards to which wood products may be exposed. A brief description of the Use Categories is shown, but if you would like additional details on the AWPA Use Category System, please download this excerpt from AWPA Standard U1.​ ​ ​ Use Category Brief Description UC1 Interior Dry UC2 Interior Damp UC3A Exterior Above Ground, Coated with Rapid Water Runoff UC3B Exterior Above Ground, Uncoated or Poor Water Runoff UC4A Ground Contact, General Use UC4B Ground Contact, Heavy Duty UC4C Ground Contact, Extreme Duty UC5A Marine Use, Northern Waters (Salt or Brackish Water) UC5B Marine Use, Central Waters (Salt or Brackish Water) UC5C Marine Use, Southern Waters (Salt or Brackish Water) UCFA Interior Above Ground Fire Protection UCFB Exterior Above Ground Fire Protection ​ ​ ​

 

[Berta]

Mike, put that in an article so we have that as a reference please.

 

[Mike Davis]

I'd rather send you the link to AWPA.

http://www.awpa.com/references/homeowner.asp

 

[Hmerkle]

Thanks for that Mike - the simple answer Jim is the copper - you are seeing "Corrosion" or verdigris that green color copper things turn when exposed to the elements!

 

[Mike Davis]

Some use copper and some do not, that's why some wood is brown.