Tag Archives: pole barn concrete

Are Concrete Piers OK in Earthquake Areas?

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays. With many questions to answer, please be patient to watch for yours to come up on a future Monday or Saturday segment. If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU:Why are concrete piers not recommended for pole buildings in earthquake areas? YELLING FROM YELM

DEAR YELLING: Part of why I love what I do for a living is I get to learn new things every day. I’d never heard of concrete piers not being recommended for pole buildings in earthquake areas – and have researched it highly, without finding any data to back up the premise.

Post frame (pole) buildings perform admirably in earthquakes as they are very lightweight, as well as flexible, compared to most other construction techniques. The heavier a structure is, the more it will be impacted by seismic forces. Most pole building construction relies upon wooden columns which are embedded in the ground (usually in concrete). A true concrete pier (a hole entirely filled with concrete) with a bracket to attach a column to the pier could prove to be a different story. In the event of a seismic event, the bracket/column connection could very well act as a hinge point.

DEAR POLE BARN GURU:I’m building a Barndominium 36×40 and I wanted to know how should I insulate the walls? Without creating a mold and moisture problem. Should I wrap what type of plastic wrap around the outside of 2×6 outer walls between R-panel? Also on the inside of plastic wrap between Sheetrock walls put R-19? And put R-30 in attic? If I wanted to put tongue and groove piney knot boards on inside walls what should I put up over insulation and 2×6 studs to nail the tongue and groove boards up to? To also help insulate walls?

Do you recommend a certain size a/c and heat pump unit for a 36 x40 barndominum ? Thank you for your help. BARNDOMINIUM BOB

DEAR BOB: As for R-values, without knowing where you are geographically, I can’t speak to what level is appropriate for your specific climactic conditions.

Walls – I would housewrap the outside of my framing, use BIBs insulation, cover the inside with clear plastic for a vapor barrier. If you intend to run the boards vertically on the inside – you can use bookshelf style wall girts to create both the insulation cavity and the support for your inside finish.

Attic – make sure to order trusses with an “energy heel” – deep enough to allow for the full thickness of the insulation to extend to the outside of the building sidewalls.

As for HVAC – your local HVAC experts can recommend the proper size unit for the cubic footage of space you will be conditioning.

Sutherlands® – Calling them Out

I have a serious case of “like” for The Home Depot®. When my children were little, every time we got near one, they would start to chant (in unison), “Home Depot…..Home Depot”.

Yesterday morning I was in The Home Depot® at Grand Junction, Colorado. It was a special moment, when a gentleman came up to me (having perhaps recognized the red Hansen Pole Buildings shirt I was wearing) and told me he had purchased one of our buildings, and was constructing it now!

It isn’t very often I get to meet one of our clients, and even rarer when they are still building – so this was great fun for me.

He related to me how he was originally intending to order his new pole building kit package from Sutherlands® Lumber in Grand Junction. They had even provided him with plans, which he had submitted to the local Building Permit issuing authorities to acquire his Building Permit.

The Sutherlands® plans (which were approved by the Building Official) had a foundation composed of throwing a 90 pound bag of Quikrete® in the bottom of the hole. The pressure preservative treated column would then be placed, and another bag of Quikrete® dumped in around the post.

Pole Barn FootingIt turns out the customer decided the Sutherlands® building was going to be inadequate. His only complaint at all with a Hansen Pole Building was the size of the holes and amount of concrete it took. Even then he admitted Hansen was a better buy, even with the extra concrete costs.

The loyal readers of this column certainly will recall my railing against concrete cookies, in earlier posts: https://www.hansenpolebuildings.com/blog/2012/08/hurl-yourconcrete-cookies/ and https://www.hansenpolebuildings.com/blog/2014/03/concrete-cookies/

In my humble opinion, what is being purported to be adequate by Sutherlands® (whether the Building Official approved it or not) is close to criminal.

Our client’s building has 40’ span prefabricated wood roof trusses, with a double truss every 10 feet. In his 30 psf (pounds per square foot) roof load, it results in each truss bearing column having to support 6860 pounds of load. Added to the fun is a soil bearing capacity of only 1500 psf.

The International Building Codes (IBC) require footings to be a minimum of a nominal six inch thickness. So let’s explore the design solution promulgated by Sutherlands®.

At 90 pounds per bag of Quikrete® it would take about 1.65 bags to make a cubic foot. If this was all poured to a nominal six inch thickness as a footing pad beneath a column, it would roughly form a two foot diameter footing. Now granted, this is not how Sutherlands® would like to see it done, however we are going to give them the benefit of the doubt.

A two foot diameter footing has an area of 3.14 sft (square feet). Multiplying by the 1500 psf allowable foundation pressure, a pad such as this would support 4710 pounds….when it needs to support 6860 pounds – it is overstressed by nearly 50%!!!

Talking with a building kit supplier (such as a Sutherlands®) who is recommending bags of Quikrete® to backfill the bottom of a column hole? Might want to really think about the design being bought into.

Bagging it? Prepare for the possibility of a roof line with some humps and bumps in it, at a future date.

When people such as Sutherlands® provide under designed buildings, it gives our entire industry a bad name. I’m calling Sutherlands® out here – and challenging them to actually provide Code conforming pole building kit packages

Concrete Pier Design

A Hansen Pole Buildings client in California has just today approved the plans for his new post frame building and poses the question:

“We are in a no frost area with no snow load, so why are the concrete piers so

large and deep??”

In response:

“The column embedment (depth and diameter of the holes) has to resist several forces, including:

Concrete PierResisting uplift – the columns, their encasement (the concrete attached to the base of the column) and the “cone” of soil above the concrete bottom collar, must have sufficient mass to keep the building from being literally “sucked” out of the ground.

Resisting overturning – prior to the engineering studies done over the past few decades, the “rule of thumb” was 1/3 of the column should be below grade. Modern research and technology has allowed this design to be far more scientific.

Keep the building from settling – while you state your building has no snow load, the information on your order has your building designed for a ground snow load (Pg) of 35 pounds per square foot. The concrete piers must be able to support the dead weight of the structure PLUS any live loads which would be applied to it. These live loads include the weight of any snow, or potential snow. Your building also is designed for a light storage load attic space. Any roof truss design with this type of load must be designed to support a 10 psf (pounds per square foot) dead load across the entire truss bottom chord (12,960 total pounds on your 36′ x 36′ building) by Code. The storage area adds another 20 psf for another 8640 pounds. All of these weights have to be distributed by the concrete encasement, to the soils beneath the building, with minimal settlement.”

In areas where frost is a consideration, the column encasement (footings) must also extend in depth below the frost line, in order to alleviate frost heaving.

Continuing with my response:

“Your building has been designed with a 2000 psf soil bearing capacity, which is higher than what is allowed by most California jurisdictions. The use of this number, has actually allowed for the concrete diameters of most of the holes to be far smaller than if a lower number had to be used.”

An engineered post frame building might appear to be “just another pole barn”.  They are, in reality, highly complex structures. All of the components of the building, down to the last screw or nail, are placed through an extensive series of calculations.  They must ensure adequacy against the myriad of conditions which a building must resist in order to be Code conforming. And, most importantly, to perform admirably for not only the original building owner, but also for future generations who will utilize the building.  The concrete piers are as important as the rest of the structure they support…to be designed “just right”.

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