Tag Archives: pressure treated columns

The Effect of Temperature Upon Concrete and Lumber

The Effects of Temperature Upon Concrete and Lumber

Every time I begin to think I could never possibly hear something new, I have to be corrected as something new crops up. In this particular instance it was a reasoning to not embed properly pressure treated columns in the ground surrounded by concrete.


Nope – wasn’t the issue at all.

Nasty inert chemicals leaching into the ground and poisoning groundwater?

Nope again.

Please read on…..

The ping pong began with an EIT (Engineer In Training) stating: “As a general rule of thumb, I cannot embed wood in concrete”.

Which, of course, got me interested in knowing more – since my young friend was recently out of a school of higher learning, I felt this would be an opportunity to find out more. To which I responded: “I’m always interested in learning. If you would not mind taking a few moments to expound upon them, I would greatly appreciate your insights as a design professional.”

Bouncing back came, “With reference to my general rule of thumb, it is the stance of my company, approximately 80 structural engineering professionals, to not embed wood in concrete. This is due to the material incompatibility that I discussed earlier. Material incompatibility, in this case, is referring to the environmental effects on two separate materials that result in different changes in physical properties. An example of this would be the effects of temperature on wood and concrete. Applying the same temperature delta to the two different materials will result in different changes in volume of each.”

“However, research material associated with the effects of temperature change and climate on wood is something that you can obtain from any introductory material on wood performance/design.”

mr owl tootsie roll popOkay, since it appears I am being schooled here (definition of schooled from www.urbandictionary.com: Being taught the proper way to perform an action, via extreme ownage and embarrassment. This requires the schooler, who is always of such a high level of skill that the schoolee has no chance of saving his reputation, to utterly dominate and show no remorse.”), it was time for me to go dig into the introductory material.”

The information on concrete was an easy find. Concrete expands slightly as temperature rises and contracts as temperature falls. Temperature changes may be caused by environmental conditions or by cement hydration (the exothermic chemical process in which the cement reacts with the water in a mixture of concrete to create the calcium silicate hydrate binder and other compounds). An average value for the coefficient of thermal expansion of concrete is about 10 millionths per degree Celsius (10×10-6/C), although values ranging from 7 to 12 millionths per degree Celsius have been observed. This amounts to a length change of 1.7 centimeters for every 30.5 meters of concrete subjected to a rise or fall of 38 degrees Celsius.

So let’s put the results into a layperson’s (someone like me) terms. In a temperature change of 68.4 degrees Fahrenheit, 18 inches (one-half the diameter of a very large three foot across concrete encasement) would expand or contract roughly 1/100th of an inch.

As this amount seems rather small, the problem must therefore lie in the column.

Pole FootingI picked Pine as my wood of choice, not only because most pressure treated columns are Southern Pine, but also because I could find a value! It turns out the Coefficient of Expansion in inches of expansion per inch of material per degree F (Fahrenheit again) is 0.0000028.

If we are talking about a nominal 6×6 timber (5-1/2 inches square) and our same 68.4 degrees we are looking at 0.00218 of an inch (roughly 1/459th of an inch).

I learned new stuff!

Which is fabulous in my book – the effects of temperature upon these two materials in combination is negligible, so minute as to be unable to be detected by the human eye!

Sliding Doors, Roofing Tar on Posts? and Condenstop!

Sliding Doors, Roofing Tar on Posts? and Condenstop!

DEAR POLE BARN GURU: I have an arena with 12×12 openings at each end. I want to find a rolling door solution. I would like to have 6.5” doors that open left and right. I’m also interested in finding a door solution that instead of tan metal (matching my building) I find translucent panels.

I can upload photos in a few days when I return to the farm.

Is this something you can help with?


building problemsDEAR JASON: If yours is typical post frame (pole) building construction, your opening probably measures 12 feet from center of column to center of column, in which case you would be looking at needing a 12 foot width split sliding door. This would give you two door leafs just over six feet in width, enough to cover the opening, provide an overlap on each side and be able to be covered with two three foot widths of steel siding.

You should be looking at a door system which has all steel girts (horizontals) and verticals, preferably pre-painted. While translucent (polycarbonate) panels could be used, I would typically not recommend them due to their not having a resistance to wracking.

In our case, Hansen Pole Buildings only provides sliding door components with the investment into a complete engineered post frame building kit package. We typically would recommend you pay a visit to the ProDesk at your local The Home Depot to acquire the parts you will need.


DEAR POLE BARN GURU: Enjoy reading your blog. I will be building in thick wet clay and am worried about post rot due to the amount of moisture. Will painting the entirety of the buried portion of treated pole in roofing tar help preserve the wood? TIM in LEXINGTON

DEAR TIM: Thank you for your kind words, I hope to be both entertaining and informative. Will painting the entirety of the buried portion of a treated pole in roofing tar help preserve the wood? Well, it might, although I have found no studies which would confirm the ability. I did find an interesting article in Scientific American, which may shoot down the idea: https://www.scientificamerican.com/article/coal-tar-and-its-products-as-preser/.

The reality of the situation is, a properly pressure preservative treated column is going to outlast all of us, and probably our grandchildren. This article should be of interest: https://www.hansenpolebuildings.com/2017/12/will-poles-rot-off/.


DEAR POLE BARN GURU: Hello guru. I bought a bunch of 1/2x4x8 sheets of insulation to put on my new 40×60 barn roof under the steel and on top of purlins .Planned on taping all seams for a moisture barrier. It’s not the really dense foam more of a bead style with a silver back on one side plastic on the other so it’s a little bit squishy. After thinking about it what worries me is that after time it may cause the barn screws seal to loosen up. If the foam lowers it could cause the steel to drop a bit. Than could create a leak under the rubber washer. Or do you think it will work ok? Should I just use Tyvek instead on the purlins? What is your opinion Guru? ABE in WAYLAND

DEAR ABE: Do not use this insulation as you have intended, it will cause you nothing but grief. Not only will your post frame barn roof leak, but the diaphragm strength of your roof steel will be severely compromised, which could lead to a catastrophic failure. Tyvek and other building wraps are not condensation control barriers, they are moisture barriers. There are several possibilities – invest in roof steel with Condenstop or Dripstop preapplied, use a radiant reflective barrier between the purlins and roofing, or spray closed cell foam on after the roof is installed.



How to Untwist a Pressure Treated Post

This actually began as an “Ask the Pole Barn Guru” question:

DEAR POLE BARN GURU: We have installed the Pressure Treated Posts  and they were straight when the concrete was poured, now a couple of weeks later we are seeing the poles twist and warp. They are straight at the ground level but about half way up they start warping. We are getting ready to put the Trusses up and want to try to get the twist and warp out as much as possible before the trusses are secured to them. What should we do for this issue? SHERI IN BENTON CITY

Twisted PoleThe series of photos on untwisted pressure treated posts are thank to Tim Fieldsend who had the very same problem back in 2003. Tim is my hero for having saved these photos for a dozen years!

When Tim contacted me with his challenge, I suggested a fix which I had not tried before, but it made some sense at the time.

The first step was to absolutely saturate the pressure treated post with water – soak it and keep it wet. Tim was creative enough to actually wrap a soaker hose around the columns!

Twisted PostAfter a few days of being watered, apply significant and steady pressure on at the top of the column, in the reverse direction of the twist. Tim’s solution sure worked, however a substantial steel bar or rod cabled or chained to the top of the column would work as well. If the post is not thoroughly saturated, there is a high probability it will snap off. As the column begins to untwist, continue to tighten the cable attached to the lever arm.

Twisted PostOnce the column has been restored to straight, keep the tension on the cable and allow the column to thoroughly dry. Once dry – get the column incorporated into a completed building as expediently as possible.

Kitty Hawk

My loyal readers know I grew up flying small planes (read more about my adventures at https://www.hansenpolebuildings.com/blog/2013/09/hangar-n3407s/).

Growing up in a flying household meant the Wright Brothers were highly revered. I’d always wondered why it is two brothers from Dayton, Ohio ended up making history at Kitty Hawk, North Carolina.

I had my first experience visiting the Outer Banks this past May. It didn’t take me but driving a few blocks down the main drag to figure out why the Wright’s came to Kitty Hawk to fly – they must have loved cheap souvenir T shirts and putt-putt golf!

Seriously, Wilbur and Orville came to Kitty Hawk due to the regular breezes and soft sandy landing surfaces.

beach houseBesides the shirts and miniature golf, there was one characteristic I noticed about many of the houses built along the Grand Banks – they are mostly built on top of platforms which are eight to ten feet off the ground and supported by pressure preservative treated wood columns embedded into the ground.

As I drove through the Kitty Hawk area, I was getting pretty “jazzed” about the whole concept – these are pole buildings!

My new found excitement was dashed, when I found one under construction and saw the treated columns did not extend above the platform.

I had to stop and talk to the builders (and snap a few photos). Asking them about the posts not being the height of the walls and all they could tell me was, “it wasn’t allowed”.

Clearly I was not satisfied with this answer, so I ventured on to the warehouse of all construction knowledge – the Pro Desk at the Kitty Hawk Home Depot. The Pro Associates there at the counter gave me the very same answer, Code would not allow columns to go past the platform.

The entire experience left me with a bad taste in my mouth. I was just not able to let this one sit, so after mulling it around for several months, it was time to go on the offensive!

I posed this question to the three Building Permit issuing jurisdictions in the Kitty Hawk area:

“I was a visitor to your area earlier this year. I noticed homes being built which were platforms on top of pressure preservative treated columns. I stopped to talk to one of the contractors and remarked how (in my simple head) it would be seemingly easier and more structurally sound for the treated columns to be extended all the way up to the roof line, rather than having a hinge point created at the platform. I was told it was “not allowed” by the Building Department. Somehow this response did not seem right, so I am inquiring to see if there exists, in your jurisdiction, some amendment to the Codes which would preclude the use of continuous columns.

 Thank you very much for your time and consideration, it is greatly appreciated.”

 All three responding nearly immediately! Here are their answers:

Buddy Shelton, Chief Building Inspector, Dare County: “IT’S NOT AN ISSUE IN THE BUILDING CODE.”

Matthew Lowcher, Chief Building Inspector, Town of Kill Devil Hills: “The type of construction method you speak about would be allowed. It just is not a typical type of construction in our area. Engineered sealed plans may be required for such a structure. The Building Code enforced in the State of NC is the NC State Building Code, which is the ICC with NC Amendments. I hope this answered your question.”

Dennis L. Speight, Building Inspector, The Town of Kitty Hawk: “I know of no code requirement, state or local, that prevents using continuous length piles.”

 My biggest takeaway from this experience is – perception and reality are not always the same thing. Both the builder I spoke with, and the supplier, were thoroughly convinced the method I suggested would not be allowed by the Code!

Orville and Wilbur made things happen which people said could not be done either!

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.