Tag Archives: Larimer County

When Pole Barns do not Have Footings

Reader KEN in FORT COLLINS writes:

“HI MIKE!

We just bought an acreage with an existing 36 x 48 post frame farm storage building. In talking to the prior owner, we have learned that the builder did not use cookies, footing pads or a cement bottom collar. So nothing to prevent settling (He did nail uplift cleats on each column. ) We are concerned about the building settling. The building is two years old and is straight and level now.

Question: Our question is if we pour a five inch thick concrete floor and install hairpin rebars in each column will this provide significant protection against settling? If not what remedy would you suggest? Your sage advice would be appreciated!”

Amazing.

I say this because Larimer County requires building permits on all post frame buildings and they are good about doing inspections. How this one escaped their watchful eye is beyond me – and sad, because now you (new to you building owner who cares) are stuck trying to solve a challenge which never should have existed.

Which leads me to – you might want to contact the county to confirm a Building Permit was issued for your post frame building and it was signed off on by the field inspectors. If it wasn’t and your building fails a smart insurance company will get out of paying a claim to replace it. You may also have some recourse against the prior owner for not disclosing the building did not have a permit.

Back to the problem at hand.

Builders like this give our industry a bad name and me headaches.

Tying the columns into a concrete slab on grade with rebar hairpins might prevent both settling and uplift forces. It might also just crack your concrete.

The best solution, in my humble opinion, is not the easiest one, which would be to excavate each column individually to eight inches below the column while supporting the building nearby. Slide an 18 inch or taller piece of sonotube up from the bottom of the column (unless you have some overly heavy roof load, loft or bonus room in the trusses 24 inch diameter should work on sidewalls, 18 on ends), place it on undisturbed soil, with the column in the center and pour the tube full of premix concrete. The soil should then be compacted around the tube and the upper portion of the excavation.

Mike the Pole Barn Guru

Prescriptive Requirements

Larimer County, Colorado

I drive through the Fort Collins area about once a year. Other than the urbanized areas, the terrain is a classic example of Exposure C for wind (for a “fun” wind exposure story read https://www.hansenpolebuildings.com/blog/2011/11/wind_exposure/ or to get more technical: https://www.hansenpolebuildings.com/blog/2012/03/wind-exposure-confusion/).

weathered pole barnOne of our clients had been discussing with Hansen Pole Buildings Designer Lily a pole building to be located in rural Larimer County. The county had provided him with a sheet of “prescriptive” requirements for non-commercial, non-residential pole barns in the county.

I’ve railed in the past about prescriptive requirements from Building Departments, so I might as well keep up my soapbox rant (visit my prior rant here: https://www.hansenpolebuildings.com/blog/2012/02/prescriptive-requirements/).

For those who want to follow along, the Larimer County handout can be viewed at: https://www.larimer.org/building/pole_structure.pdf).

Let’s take a look at the “non-high wind” requirements.

Building is limited to 35 foot clearspan with engineered trusses. Columns are to be placed every eight feet. Footprint can be up to 3000 square feet. Maximum wind speed is 110 mph.

Now the catch in this is the statement in the handout, “All framing elements are to be designed in accordance with accepted engineering practice”. Which seems contrary to buildings utilizing the “basic handout design”.

With an eave height of 14 foot and a 4/12 roof slope, columns would need to be 6×10, IF diaphragm design is used, otherwise 6×12. I say “IF” because the handout makes no provisions for how to utilize diaphragm design.

In either case, all is well and good, except getting a solid sawn column larger than 6×6 in Colorado is a challenge unto itself.

The treated hold down cleat is not likely to provide sufficient resistance to uplift to resist 2512 pounds. A sophisticated engineering analysis would be required for proof. Read more about column uplift here: https://www.hansenpolebuildings.com/blog/2012/02/concrete-collars/

The 2×6 wall girts at 24 inches on center will work to carry the wind load (stressed to just under 96% of capacity), however deflection using the common framing lumber with a MOE (Modulus of Elasticity) of 1,300,000 is over in the deflection department by nearly 35%. It would take a MOE rating over 1,800,000 to meet the deflection requirements. (Read about girt deflection here: https://www.hansenpolebuildings.com/blog/2012/03/girts/)

The interior truss to column connection, must be able to withstand 4411 pounds of uplift force. Considering a Simpson Strongtie (https://www.strongtie.com/products/connectors/HRS-ST-PS-HST-LSTA.asp) HST2 7 gauge steel plate with six 5/8” diameter through bolts will only support up to 4835 pounds, it is not possible to imagine the two ½” carriage bolts (as specific in the handout) as being anywhere close to adequate.

To reiterate my basic premise: If a Building Department has PRESCRIPTIVE REQUIREMENTS for Pole Buildings – invest in an engineered building kit. It is less expensive to pay for the engineering and it guarantees a building which will be designed to actually meet the building codes!