Tag Archives: AWPA



Reader MIKE in ORLANDO writes:

“Dear Pole Barn Guru,

I bought a 38×42 Pole Barn kit from a reputable supplier. The posts are 8″ x 8″ – but do not have the AWPA markings that you describe in your Blog. These posts have a tag stapled to the end that says “SPLASHWOOD, Saltwater Splash Use Only, .80 PCF, Chromated Copper Arsenate (CCA-C), Southern Wood Preserving, Inc,.” and a paragraph of cautions and Consumer Information. I tried to look up this info to see if these posts are AWPA UC4B equivalent but could not find any info on-line.
Are these post acceptable for my Pole Barn construction?

Mike the Pole Barn Guru writes:

Splashwood™ happens to be a registered trademark and brand of Great Southern Wood Preserving, Inc., and was filed December 30, 2004. Great Southern Wood Preserving, Inc., is based in Abbeville, Alabama and was founded in 1970. It has 15 plants located in Alabama, Arkansas, Florida, Georgia, Mississippi, Missouri, Louisiana, Maryland, Virginia, Pennsylvania and Texas with annual revenue of a billion U.S. Dollars.

Pressure-treated wood is treated to various retention levels which are intended to protect the wood for particular applications. Retention levels indicate the amount of preservative retained in the wood in a specific assay zone. In North America, retention is expressed in pounds per cubic foot (pcf).

Retention levels or treating quality procedures are marked on pressure treated wood. The AWPA (American Wood-Preservers’ Association) outlines retention levels required for various applications.

Retention varies with depth in the wood, so preservative penetration also affects wood longevity. In species with large amounts of sapwood, such as southern and red pine, the preservative must penetrate 2.5 inches or 85% of the sapwood to meet standards.  In western species which are predominately heartwood, the wood is incised to ensure a treated shell, and any cut surfaces should be field-treated with a preservative containing at least 2% copper (read more about cut ends of treated lumber here: https://www.hansenpolebuildings.com/2014/09/pressure-treated-lumber-2/).

To meet the Code required standard of UC-4B for structural timbers, takes a retention of 0.60 pcf with CCA. The pressure treatment of your columns exceeds the minimum requirements.


Incising Lumber


My former wife (mother of my two youngest children – Allison and Brent), was by training an RDH (Registered Dental Hygienist). In order to keep her registration current, she had to obtain CEUs (Continuing Education Credits). One way to generate CEUs was to attend the annual state dental convention.

One year I went along with her and as we perused the trade show floor, the assumption was somehow made of me being a dentist – so I received lots of attention. Also tons of free stuff – I don’t think I needed to purchase a tooth brush, tooth paste or dental floss for the next decade!

Other than my annual visits to the dentist, about the only thing I remotely knew in regards to teeth were the incisors are the front four teeth on the top and bottom.

With my tremendous knowledge of incisors – I was able to easily translate to incising of lumber.

For those in the east and south – you may have never seen pressure preservative treated lumber which has been incised. Most treated lumber in those regions is Southern Yellow Pine – which is highly treatable (think of it as being a chemical sponge).

Travel west and north, the lumber species of choice for pressure treating is grade stamped as Hem-Fir. Hem-Fir is not a species unto itself, it is a lumber species “group” which includes California Red Fir, Grand Fir, Noble Fir, Pacific Silver Fir, Western Hemlock and White Fir.

Incised LumberDifficult-to-treat (refractory) lumber species, such as Hem-Fir, must be incised prior to preservative treatment to meet minimum penetration requirements for preservative-treated wood. Incising is a pretreatment process in which small incisions or slits are punched into the wood. To me, the resultant product looks as though the lumber has been walked on by someone wearing golf shoes!

Incising increases preservative retention and penetration during the treating process by increasing the amount of exposed, easily penetrated end-grain and by decreasing the side-grain surface area. While incising has been used since the 19th century, the process appears to have developed casually with little consideration given to optimizing the process to maximize preservative treatment and minimize strength loss. While AWPA (American Wood Preservers Association) standards require incising, they do not define or recommend what type, how deep, or how many incisions are required. Generally, it appears the more effective an incising pattern is in achieving preservative penetration, the more it reduces strength.

AF&PA’s National Design Specification® (NDS®) for Wood Construction includes provisions for the downward adjustment of lumber strength characteristics for incised lumber by use of an Incising Factor known as Ci. Referenced design values are multiplied by Ci when dimension lumber is incised parallel to grain a maximum depth of 0.4”, a maximum length of 3/8”, and a density of incisions up to 1100 per square foot.

E values are to be multiplied by 0.95, while other values (with the exception of compression perpendicular to the grain of the wood) are multiplied by 0.80.

Sound engineering design of incised lumber (which includes pole building columns) take into account these strength reductions.

If you see Hem-fir and it has all these little cuts – don’t panic. It just means it’s been incised for adequate infiltration of chemical treatment. This ensures preserving a longer life of whatever you are building, be it a deck, garage or even a new pole building house.