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Pole Building

Updated on September 26, 2015
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Pole Building Plans

Pole Buildings are popular in agricultural applications. Weather can wear down equipment by cracking seats, hoses, and other components. Rain and dust can similarly degrade the value of equipment.

One of the most cost-effective methods to protect equipment and livestock is the pole building. Plans are simple: pipe columns sit in pier footings at the base, and attach to a roof diaphragm of steel W-beam rafters, light gauge Z purlins, and R-panel or corrugated steel roofing material.

These roof-only shade buildings can be used to shade and/or protect livestock, equipment, and feed supplies.

So, what should be considered in designing and building a pole building?

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Impact Potential

When shades are used for parking, hitting a column is a rare occurrence. However, when cattle are housed beneath pole building shades, or when hay or other feed is stored beneath a shade, work equipment make frequent shuttles in and out of the columns. Occasionally, one of these columns can be struck. There are three common solutions to prevent a bent pole.

First, the most common method is to supply a heavier column. For example, a 5" standard weight column (schedule 40 pipe) increases to 5" Extra Strength (XS, or schedule 80) pipe. Or a 6" Standard Weight pipe might increase to 8" standard weight.

Second, a method cheaper in material, and only slightly more expensive in labor, is to splice the column 4 feet above the ground or slab. For example, in a tall storage building, with 20-foot columns, an 8" Std Wt column is increased to 8" XS in the footing, and up to 4 feet outside of the concrete. The upper portion, which is very unlikely to ever by struck by a bumper or loader, remains 8" Std Wt.

Third, the column base can be encased in concrete. The concrete should be at least 6" thick, with a cage of #4 rebar hoops and 3 to 5 vertical bars. This is above ground, and should be about 4' high. A lightweight mix is friendlier to vehicles. Because this is not a structural component, the rebar may be omitted. Over the years, impacts knock concrete loose, and will expose the rebar. Exposed rebar is less forgiving than concrete in an impact or sideswipe.

Which Pole Barn?

If you are planning on building a pole barn in the future, which of these will it be?

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Most Common Pole Barn Plans

The most common pole barns (true pole barns, not steel buildings constructed economically with pipe columns and wide-flange rafters) are these:

  1. Shade Barn, Cattle Shade
  2. Hay Barn
  3. Shade Barn, Equipment
  4. Freestall Barn
  5. Horse Arena
  6. Loafing Barn

Splicing Pipe or W beam sizes of different weights

When splicing together two pipe sections of the same nominal size (outside diameter) and different wall thicknesses, form the weld using a throat equal to the thickness of the smaller section. These welds must be groove welds. Grind the smaller pipe to form a mitered edge (45-degrees).

When splicing two steel sections of the same dimensions but different thickness, weld to match the thinner section.
When splicing two steel sections of the same dimensions but different thickness, weld to match the thinner section.

Column Number and Spacing

Obvious locations of column lines are along feed lanes, along fence lines, and at the haunch of the rafters. Keeping space between columns in a frame close to 20' produces lighter rafters.Smaller buildings, say with less than a 40-foot span, are usually constructed with a free span. Over 40 feet in span, it may be more economical to add a third column beneath the ridge.

Roof-only pole barn shades like hay barns and freestall barns collect far less wind than shops and other enclosed metal buildings. Because of this, the engineered size of rafters, columns, and footings is often controlled by the loads imparted by the self-weight of materials (dead loads), and anticipated construction loads (live loads).

The combined force of dead and live loads creates a bending force which controls the rafter and column sizes. If column lines are not dictated by locations of stanchion lines and lanes, it is possible to minimize rafter sizes by calculating the most advantageous location of columns so that bending moments are balanced and minimized. This technique works well for hay barns and roof-only shades.

Hay barns lend themselves well to optimized column spacing. However, this spacing is usually dictated by the width of hay bundles to be stored. In Central California, this is usually two trips of a full forklift.

Pole Building Plans

Evenly spaced columns reduce rafter sizes. This building uses only a W10x12 rafter. It is 141 feet out/out on the 8" columns.This is a polyvinyl roof system, utilizing special construction and building code exceptions.
Evenly spaced columns reduce rafter sizes. This building uses only a W10x12 rafter. It is 141 feet out/out on the 8" columns.This is a polyvinyl roof system, utilizing special construction and building code exceptions. | Source

Removing Columns in End Frames

Most pole building plans are the same, frame to frame. However, there may be a need to alter some frames.

Occasionally, columns on end frames may differ from the number and location of columns in frames within the interior of the shade. One reason to omit columns in end frames is that the load entering the frame is typically only half that of the main frames. Another reason is to provide for the turning radius of a scraper or a feeder. Columns are sometimes adjusted in the end frames to accommodate water troughs or flush gates.

When columns are omitted, rafter spans increase. In turn, the size of the rafter may also increase. This effect is minimized on the end frames because of the reduced roof area tributary to those rafters.

A 60x120 hay barn like this one can be optimized for lightest members by balancing moments. Column spacing here is 33' c/c columns, and 13'6" overhang on each side.
A 60x120 hay barn like this one can be optimized for lightest members by balancing moments. Column spacing here is 33' c/c columns, and 13'6" overhang on each side.
Timber Frame Construction: All About Post-and-Beam Building
Timber Frame Construction: All About Post-and-Beam Building

There is also a Kindle version of this book available for immediate access. (You can download free Kindle viewers for PC, Mac, and Ipad/ipod devices.) This is a #1 best seller.

 

Solar Panels for Barns

Recently, I have been engineering many existing barns for the added dead load of solar panels.

The addition of solar panel arrays to roof-only pole barns and to shops is a smart move for ranch and dairy owners. These agricultural facilities already have the support structure and roof area to add the panels. Additionally, to create the best shade effect, most buildings are oriented to intercept the sun's rays.

If you believe you may want solar panels in the future, be sure to convey this to your engineer.

What is a Pole Barn?

There are two definitions of a pole barn in use. Each has a different place and application. First, and more widely known, is the term which refers to a barn constructed of wooden poles buried into the ground. This is usually the only foundation, although concrete is sometimes poured around the poles. This terminology evolved in the usual way. After WWII, there were excess wood poles available on the market. Savvy contractors bought up this cheap wood (they way they buy up used drill stem pipe today) and this prominent characteristic became descriptive of barns built with wooden or steel cantilevered columns: pole barns. Simple enough to understand, right?

The second definition involves the code, and can be confusing (for pedantic code enforcers, mostly). For some reason, some reviewers (the minority) look at a building with pipe columns and think "pole... it's a pole barn, and that means cantilevered columns." A cantilevered column is basically a flagpole. It is buried in the ground, with a concrete pier as an anchor, usually, and just rises up into the air. At its top, it is attached to nothing, except for maybe a brass ball or a sign proclaiming fast food or competitive gas prices.

Here is a definition provided by the International Code Council and the Structural Engineers Association:

Cantilevered Column System: A structural system relying on column elements that cantilever from a fixed base and have minimal rotational resistance capacity at the top with lateral forces applied essentially at the top and are used for lateral resistance.

Compare this to another definition, also from the 2006 Structural/Seismic Design Manual:

Building Frame System: A structural system with an essentially complete space frame system providing support for vertical loads. Seismic force resistance is provided by shear walls or braced frames.

So, a shop with X-bracing in the walls to resist seismic and wind forces is not a cantilevered system. A building with girts transferring loads into the columns below the top of column is also not a cantilevered column.

A true cantilever is free both to rotate and to translate. However, in a roof-only pole barn, the type sometimes mistaken for cantilever columns, pipe columns are attached to a roof diaphragm. The roof diaphragm allows some translation. But, the fixed (by welding or bolt groups) column tops cannot rotate.

Look at the following table, taken directly from engineering manuals. Look at type (c) and at type (e). Type e is a true cantilever. It can bend to any side. As it bends, the tip will point in a vector increasing deviating from 90 degrees to its base. Type c is the model for a roof-only pole barn. When wind hits the roof, it will push the columns laterally. However, the tip of the columns will always point upward at 90 degrees from the ground. For a column on one side of the barn to freely rotate, it would have to lift up the entire roof, breaking the connection of all other columns in the frame. For this reason of physics, roof-only pole barns are not cantilever columns. They are type (c) columns when it comes to Table C-C2.2.

Type (e) is a cantilever column. Type (c) models columns rigidly attached to a roof.
Type (e) is a cantilever column. Type (c) models columns rigidly attached to a roof. | Source

Most Common Pole Barns

The most common types of pole barns are:

  1. Cattle Shade
  2. Freestall Barn
  3. Equipment Shade
  4. Horse Arena
  5. Personal Vehicle Parking
  6. RV Parking
  7. Event Canopy

On a Scale of 1-5, How Important is a Cattle Shade?

5 out of 5 stars from 1 rating of Pole Barns/Roof-Only Shades

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    • Steel Engineer profile image
      Author

      Steel Engineer 5 years ago from Kiev, Ukraine

      Peg,

      It can definitely be done with wood columns, and with trusses. It is more expensive to construct, but it is possible. Typically, for barns, a "W" truss is used. That truss model is unique to barns because there is no load to the bottom chord (no ceiling), so only the roof loads need to be transferred to the columns.

      Wood is a strong material in bearing (as a column), so a 4x4 can work on a smaller barn, with moderate spans between columns, and moderate bay spacing between frames.

      I also engineer wood barns. Recently, it has become popular to renovate old barns for commercial use as wedding and reception sites (or other parties).

    • PegCole17 profile image

      Peg Cole 5 years ago from Dallas, Texas

      We started off with a pole barn when we first moved out here to the country but we used 4 x 4 wood for the poles. It was a bigger job than we originally thought when we decided to do it ourselves. Had the roof trusses built and delivered. Still standing though and makes a nice man cave.

    • TIMETRAVELER2 profile image

      TIMETRAVELER2 5 years ago

      Years ago my husband and I started to build a pole home. Due to extenuating circumstances, we never finished it. This article reminded me of that time, and I'm glad you wrote it. Nicely done.