Tag Archives: wood treatment

Wood Preservative

What I Learned Today – Wood Preservative

Hansen Pole Buildings’ Designer Rachel had an interesting story today.

She reported, “A builder says he uses Borax around the bottom of the steel.  I thought this was strange and he didn’t say why he was using it.”

Being the naturally curious sort, Rachel started researching on the internet, and this is what she found:

Pressure preservative treated lumber is what most of us recognize as a piece of treated wood. The treating process forces chemicals, under pressure, into the wood fibers – which inhibits decay by making the wood inedible to termites and impervious to mold and decay fungi.

BoraxRachel discovered raw (untreated) lumber can be manually treated with a solution of 10 ounces of 20 Mule Team® Borax dissolved and well mixed into a gallon of water. Once mixed, the Borax solution is to be sprayed onto lumber and a gallon should do about 250 board feet of lumber.

Me, being old enough to remember “Death Valley Days” presented by Ronald Reagan or Dale Robertson and narrated by Merle Haggard – this is the only other thing I associated with 20 Mule Team® Borax.

In doing further research, I found that boric acid of borate treatments kills the protozoa which live in the digestive tracts of termites. Since those protozoa are responsible for digesting the wood a termite eats, their death makes it impossible for termites to garner any nutrition from eating. However, unless borate treatments are applied when a structure is built, they should not be used. Borate treatments applied to established buildings are largely ineffective.

Some wood treating industry experts claim there is a wood preservative which is cost effective, performs well and is environmentally friendly, the “perfect” preservative – borates. The chemical was supposedly so non-toxic, one could drink it.

When CCA (Chromated Copper Arsenate) was generally removed from the marketplace (other than for limited specific uses), chemical companies began a mad dash to develop a binder which could prevent borates from leaching.

Attempts were made to encapsulate the borate in wood using sodium silicate to reduce its exposure to conditions which would leach the borate. Cost considerations to install equipment at the production level and increased treatment costs seem to be some reasons this ‘miracle borate’ did not advance within the industry.

In addition, the industry learned permanently locking borates into wood wasn’t necessarily a good thing. If borates stop migrating, they stop killing the fungi and insects. Borates don’t kill on contact, like spraying on a can of Raid. They act as a drying agent; they dry out the insides of an insect so it can’t eat any more. If borates are fixed permanently in the wood, experience has shown us the wood preservative will not be effective. The borate needs to be mobile in the wood in order for it to be efficacious against decay and termites. It may be possible to develop a semi-fixed borate where the diffusion process is greatly slowed down. So far, no developer of this style of borate wood preservative has opted to commercialize it, however.

While its solubility may prevent borates from becoming an all-purpose super-treatment, the same characteristic of preservative mobility also helps borates diffuse throughout the wood after treatment to effectively serve its protective purpose. The end use of the product is quite specific and limited: a service condition in above-ground applications which is protected from continued exposure to water.

My conclusion – the builder may be doing his “magic” by sprinkling 20 Mule Team® Borax around the base of a completed building, however the reality is, it is “far more show…than go”! Look for proper wood preservative methods by purchasing properly treated wood.

PCP Treated Poles

I first became involved in the post frame (pole) building industry over three decades ago, in the Willamette Valley of Oregon. At the time, many of the region’s pole barn builders were buying the lumber for the pole buildings they were selling to consumers from Withers Lumber in Brooks, Oregon.

The “special” thing about this particular lumber yard is they maintained a tremendous inventory of timbers (4×6, 6×6, etc.) which were treated with a product called pentachlorophenol, or “penta”.

First produced in the 1930’s, penta (aka PCP) is used as a pesticide and also as a disinfectant. PCP is produced by the chlorination of phenol in the presence of a catalyst such as anhydrous aluminum or ferric chloride at temperatures approaching 200 degrees Celsius. Phenol (also known as carbolic acid) was first extracted from coal tar, but today is produced on a large scale using a series of processes which begin with crude oil. Phenol requires careful handling due to its propensity to cause burns.

As a wood preserving agent, raw wood (poles or timbers) are placed in a treating tube, where they are immersed in PCP and subjected to pressure – forcing the chemical into the wood. Utility poles, treated with PCP, have an approximate useable lifespan of 35 years.

Short-term exposure to large amounts of PCP can cause harmful effects on the liver, kidneys, blood, lungs, nervous system, immune system, and gastrointestinal tract. Elevated temperature, profuse sweating, uncoordinated movement, muscle twitching, and coma are additional side effects.

Contact with PCP (particularly in the form of vapor) can irritate the skin, eyes, and mouth. Long-term exposure to low levels such as those which occur in the workplace can cause damage to the liver, kidneys, blood, and nervous system. Finally, exposure to PCP is also associated with carcinogenic, renal, and neurological effects. The U.S. EPA (Environmental Protection Agency) classifies PCP in group B2 (probable human carcinogen).

The pole builders (as well as the lumber yards) who were espousing how wonderful penta treated posts were, exposed themselves and their employees to PCP by direct skin contact.

Since the early 1980s, the purchase and use of PCP in the U.S has not been available to the general public. Nowadays most of the PCP used in the U.S is restricted to the treatment of utility poles and railroad ties. In the United States, any drinking water supply with a PCP concentration exceeding one part per billion must be notified by the water supplier to the public. Disposal of PCP and PCP contaminated substances are regulated as hazardous wastes.

This, in itself, is plenty of reason why I would never, ever consider the use of a used penta treated utility pole in any portion of a pole barn.


Pressure Treated Posts: 1807.3.1

Not near as exciting as 867-5309, but this one Section of the International Building Code (IBC) is one of the most important and least understood sections.

The American Wood Preservers Association (AWPA) addresses in, Section UC4 wood, which is pressure preservative treated for “Ground Contact”. The “UC” is short for “Use Class”.

UC4A is for “General Use”. This is “Wood and wood-based materials used in contact with the ground, fresh water, or other situations favorable to deterioration. Examples are fence posts, deck posts, guardrail posts, structural lumber, timbers and utility posts located in regions of low natural potential for wood decay and insect attack.

UC4B is for “Heavy Duty”. This is “Wood and wood-based material used in contact with the ground either in severe environments, such as horticultural sites, in climates with a high potential for deterioration, in critically important components such as utility poles, building poles and permanent wood foundations, and wood used in salt water splash zones.”

Neither of these clearly identifies which degree of pressure treating should be utilized for structural in ground use – to support a post frame (pole) building.

When the first IBC was published in 2000, Section 1805.7.1.2 stated, “Wood poles shall be treated in accordance with AWPA C2 or C4. This language remained the same in the 2003 IBC. The AWPA C2 and C4 standards have been withdrawn, therefore are no longer applicable or referenced standards in later editions of the Code.

In the 2006 IBC, however, things changed. Section 1805.7.1 states, “Wood poles shall be treated in accordance with AWPA U1 for sawn timber posts (Commodity Specification A, Use
Category 4B) “. In the 2009 IBC (and repeated for the 2012 edition), the language remained the same, however the referenced section of the Code is now 1807.3.

What does this mean for the average consumer who is shopping for a new pole barn? Everything!

Visit the local lumberyard, or big box lumber store. Take a walk through the pressure treated lumber department. Every piece of pressure preservative treated lumber has a tag on it. This tag identifies who the pressure treater was, as well as the level of pressure treating. Sadly, most of the pressure treated posts will be treated only to UC-4A….which does NOT meet with the Code requirements for use in pole buildings! It is very likely the lumberyard sales people do not realize this to be the case.

Even more frightening, most Building Officials are unaware of this requirement!

When shopping for a new pole building, ask what level of pressure treatment the pressure treated posts are treated to. If the company being contacted does not know, will not tell, or says they are “treated for structural in ground use” (or similar language), or anything other than UC-4B…run, do not walk away!

In order to have a Code conforming building, and one which will last the lifetime it is designed for – demand a minimum UC-4B pressure treating level for all structural load bearing columns.