Tag Archives: pole barn uplift

Up-Lift Plates for Pole Barns

Having spent two decades directly involved in the prefabricated metal connector plated roof truss industry (with titles running from just above the janitor, to owner of two plants) steel truss plates have always fascinated me.

Up-lift PlateFrom Pro-Footer® comes the UP-Lift plate, which is an ingenious adaptation of truss plate technology. They are designed to help save time, money and meet or exceed post uplift requirements. The affordable plates are field applied to opposite sides of an embedded column, with just a framing hammer. No special tools are required.

The numerous metal teeth of the plates ensure a firm attachment to wooden columns. The galvanized coating of the UP-Lift plate ensures extra protection and long life.

Once the UP-Lift plates are positioned, the columns can be placed in the augured holes, braced and the hole backfilled with concrete as specified by the RDP (Registered Design Professional – architect or engineer).

The accepted bond strength of concrete to wood is 30 pounds per square inch (read more at: https://www.hansenpolebuildings.com/blog/2013/04/pole-barn-post-in-concrete/). In the example in the article, a 4×6 (3-1/2” x 5-1/2”) column surrounded on the lower 10 inches with concrete would provide the ability to resist 5400 pounds of uplift force from the connection itself. This condition is known as a “bottom collar”.

Pro-Footer has a detailed analysis done on the capacity of the UP-Lift plates. For those with the “need to know more”, the analysis can be read here: https://pro-footer.com/pdf/Uplift_Plate_Analysis.pdf

For those who are taking the short version of the course, the result is a pair of UP-Lift plates attached to the column provided 8888 pounds of uplift resistance, or 164% of the concrete only design solution.

Before looking at the UP-Lift plates as the total “solution” to uplift issues, a complete and detailed analysis of the column embedment should be undertaken by an RDP, as many other factors influence the system’s ability to withstand uplift forces. These include (but are not limited to) design wind speeds and wind exposure, soil bearing capacities, building dead weight as well as how the area of the column above the concrete lower collar is backfilled.

Unsure of the ability of concrete to bond to wood? Then UP-Lift plates may be the solution for you. Please note, this product does not carry an IBC ESR approval, so may not be accepted in all Building Department jurisdictions.

Mona Lisa Smile: Concrete Cookie

Client calls into our office at the end of the day Friday and talks with Sheila. He tells her his Building Official will only accept his new pole building construction with holes 48 inches deep, with a six inch thick concrete cookie in the bottom of the hole, and no concrete backfill around the columns.

Here is some background….

The building is a commercial pole building 34’ x 60’ x 13’ in Iowa. Because it is a commercial building, the client purchased engineered plans for the building, which includes all of the supporting calculations for the design.

While a hole for a pole building post might seem to be just a hole in the ground, lots of things are happening below the ground. The embedment has to be deep enough to put the bottom of the footing below the frost line. The footing beneath the column has to be large enough in diameter to keep the building from settling. The design must also provide for the resistance for uplift.

In this particular building, the downward load on the footing is just over 5400 pounds. The uplift force is 1120 pounds.

Now it is 4:50 on Friday afternoon, so I ask for the phone number for the Building Department, client instead, has me call him…..now the Paul Harvey appears….

The issue turned out to have absolutely nothing to do with any Building Official, and everything to do with the client’s builder (I know, a shock).

The builder insists upon digging the holes with the 12-inch diameter auger he has mounted on the back of his farm tractor. He refuses to set the posts in concrete, because if he doesn’t get a post in the right place, he wants to be able to move it around in the hole. His idea is to dig a four foot deep hole, and drop a 12-inch diameter concrete cookie in the bottom of the hole!

I can foresee a myriad of potential problems coming up, even without breaking out my Ouija board, or shaking the Magic 8 Ball.

Problem Numero Uno – if these holes are approved by the field inspector, someone is either blind, or an envelope got passed. If the Building Department accepts anything which is contrary to the engineer sealed and approved plans, they have opened themselves up for an entire world of liability.

Assuming somehow they are able to pass the hole inspection – a 12 inch diameter concrete cookie covers roughly 0.76 square feet of surface. Applying a load of 5400 pounds to it, means the soil bearing capacity would need to be somewhere in the neighborhood of 7000 pounds per square foot (psf). Table 1804.2 of the International Building Code gives a value of 4000 psf for sedimentary and foliated rock and 12,000 psf for crystalline bedrock. Neither of these types of soil would be touched by the 12-inch farm tractor auger. The probability of settling issues on one or more of these columns – right darn close to 100%.

The diagonal distance across a 6×6 (actual dimensions 5-1/2” x 5-1/2”) is nearly eight inches. Those 12-inch diameter holes better be pretty much spot on and perfectly plumb, or there are going to be some very interesting looking walls (as in not very straight at the ground line).

Builder does not want to backfill any of the holes with concrete (builder says it will also rot the posts) to prevent uplift. With a hole this tiny, there is no way to even begin to attach an uplift cleat to the sides of the columns.  There is also no way to adequately tamp compactible materials into the space between the column and the sides of the hole.

A registered design professional has designed this pole building. He has years of experience and has designed literally thousands of successful buildings. At his fingertips are the most powerful computer design programs. This design is nothing short of a work of art.

The resultant, we have the Mona Lisa being whitewashed over by a builder with a farm tractor.