Tag Archives: pole building footings

Pole Barn Footings

Some things in life amaze me – magicians are one of them. I have no idea how the do what they do, but I am totally fascinated by them (you can read about my college experience with a magician here: https://www.hansenpolebuildings.com/2014/08/lumber-bending/). One of the other things which amaze me are how clients will invest tens (or hundreds) of thousands of dollars on a new post frame building, only to cheap out on the footings!

Anything of high quality requires a good foundation.  In post frame buildings, the measure of a good foundation’s investment is small in comparison to the overall picture.

Reader CHRISTINE from SPOKANE writes:

“We see all these posts about footings. It seems here they just pour concrete around post with no footings. Is that due to the nature of our rocky soil. Our posts are in the ground, no footing and ready for concrete, architect plans, say “bottom of all footings to bear on undisturbed ,native, inorganic soil 1′ min below grade. Extend all footings 4′ min below finish grade.” Did I assume wrong and he’s calling for an actual footing? TYIA! ASAP”

Dear Christine;

For years we designed our post frame buildings without a concrete footing below the columns, instead relying upon the concrete encasement around the posts to adequately bond to the pressure preservative treated column. The bond strength between concrete and wood is documented and more can be read about it here: https://www.hansenpolebuildings.com/2013/04/pole-barn-post-in-concrete/. There were some Plans Examiners who did not look kindly upon this as a design solution.

The Building Codes do specify the requirement for a concrete footing, and as such we moved several years ago to a design which placed eight inches thick of concrete below the column.

As an architect designed your building and placed his seal upon the plans, you are obligated to construct the building per his/her solution. There should be a detail on the plans which shows exactly what the architect had in mind. If there is not, request a clarification as this is something you paid for in your fee for the work.

Mike the Pole Barn Guru

Looking for a post frame building with a column embedment design which both makes sense and works structurally? If so, only consider a building which comes with plans done specifically for your building, on your site, and sealed by a Registered Professional Engineer.

FootingPad System for Pole Barns

FootingPad™ Composite Footing System

In the early 1980’s I was a member of the Board of Directors for the National Frame Building Association (NFBA). Serving along with me was Glen George.

The recent 2014 National Frame Building Expo held in Nashville, TN, was like old home week for me, as I reunited with several people I hadn’t had a chance to talk with in years. One of these was Glen.

My loyal readers have read me rant on about concrete cookies attempting to be used as footing pads for columns in pole buildings. For those who have missed the fun, here is a chance to catch up:

https://www.hansenpolebuildings.com/blog/2012/08/hurl-yourconcrete-cookies/

https://www.hansenpolebuildings.com/blog/2014/03/concrete-cookies/

Welcome back.

I have always respected Glen as being a pretty sharp person. In this case, I was not at all disappointed, as Glen and his team have seen a need and developed an alternative to the infamous concrete cookie.

They have developed a composite footing system which is engineered to provide the fastest and most economical method to support the structural building columns for many pole buildings.

FootingPads have been designed and engineered to replace concrete footings of equal diameter. They have been thoroughly tested and certified by NTA Testing Laboratories and carry the ICC-ES Evaluation Services approval (ESR-2147). (Read more about ESR numbers at: https://www.hansenpolebuildings.com/blog/2012/01/icc-es/)

footing padFootingPads are available in both 16 and 24 inch diameters. They won’t crack like concrete and no extra or special equipment is required.

The one downside is currently mechanical fasteners cannot be used to attach FootingPads to the bottom of a column, which prevents them from being used to prevent column uplift. This requires the RDP (Registered Design Professional – Architect or Engineer) to design an alternative means for resisting uplift forces. Considering most providers who specify concrete cookies appear to entirely ignore uplift – most anything would be an improvement.
In today’s world of “green building” the FootingPad composite footing system makes the most sense in minimizing environmental footprints, while maximizing structural integrity. Each FootingPad is manufactured from 100% recycled composite materials. From manufacturing to transport and installation, every FootingPad is completely eco-friendly!

Sonotubes

Coulomb Theory

As I have probably mentioned a few times, I learn new stuff every day. Sometimes, what I learn causes me to rethink my prior positions on subjects. I’d like to believe this is a good thing, as it keeps me from being so rigid.

Concrete Form TubeI’ve always had a bad attitude toward the use of sonotubes placed in holes of post frame buildings. People’s thought is generally – I have dug a very big hole, I don’t want to use so much concrete in the hole, so I will put a sonotube in the hole, and backfill around the tube.

I’d always looked upon this rather like the ancient Roman adage, “It’s all fun and games until someone loses an eye”. To me, it was all fun and games until the pole building column and the sonotube get sucked out of the ground like a cork from a champagne bottle.

What started me on this particular trek was doing frost heave research. I’d read some work done by engineer Harris Hyman, who appears to be the expert on the subject.

I am reading along in one of his papers, where he is talking first about anchoring a post to an oversized footing to prevent uplift. The idea is that the weight of the earth above the footing will hold the post down, and if the footing is sufficiently deep (like below the frost line), no heaving will occur.

Well, Harris has another idea:

There is another option that may have more promise for post construction: Forget the footing, but put the post in deep enough to resist lifting by the friction of the earth. The earth exerts a lateral – sideways – force against the surface of a wood post or sonotube. Friction between the earth and the post causes the post to move with the earth. As the post goes deeper, the lateral force of the earth increases, creating greater and greater friction against the sides of the post and holding it in the ground.

The Coulomb theory of earth pressures shows that the friction against the bottom third of the underground portion of an embedded post is equal to the friction against the top two-thirds. By this reasoning, if the post is not to move, the bottom one-third (or a little more) must be below the frost line. With a 4-foot frost line, a 6-foot or deeper post depth is needed, so that at least 2 feet, or one-third, of the embedded part of the post is below the frost line.”

Now, please keep in mind, Mr. Hyman was writing only in regards to combatting forces from frost heave, however the same theory of earth pressures could be used to resist wind uplift as well. An important factor in calculating the needed embedment of columns is the square of the dimension of the column (or its concrete encasement). If an unencased column was used, the depth would end up being proportionately greater than one with concrete backfill.