Pole building framing
Pole framing and Pole building framing, commonly known as Pole building (from "Pole Barns" or "Pole buildings"), is a simple building technique adapted from the labor intensive post-and-beam construction technique. It uses large poles (or squared off posts) buried in the ground to provide the vertical structural support and strong "girts" parallel to the floor to provide horizontal support. The method was developed and matured during the 1930s as changes in agricultural practices, including the shift toward engine-powered farm equipment, created demand for cheaper, larger barns and storage areas. Unlike competing building methods, once the poles, girts, and rafters are put in place, much of the construction work on a pole-built structure can be handled by a single individual over the course of a month or season.
Pole building design was pioneered in the 1930s originally using rounded utility poles for horse barns and agricultural buildings. As the practice took hold, rather than using utility poles, materials were developed specifically for this type of construction, making the process more affordable and reliable. Today, almost any low-rise structure can be quickly built using the post-frame construction method.
When poles (debarked, delimbed tree trunk sections) are used, girts and shims are added to square the structure for hanging the wall curtain. Normally, a type of vertically hanging siding such as galvanized corrugated sheet steel or board and batten siding was used. The girts are substantial structural members. Along any given wall they must collectively bear the weight of the exterior wall and anything hung from it. On at least two walls this includes part of the weight of the roof. In a modern pole built office building, or other buildings requiring interior walls and subdivisions, interior girts would usually be added. Each girt is a bearing member, sharing and carrying the weight of interior walls and mountings to the posts. In animal husbandry, interior girts are more likely to resist the thrust of animals jostling in a common pen. To add a second floor or loft, joists laid down at right angles to the girts readily make up a new floor level.
On two walls, usually the long wall, the heavy "beam" function of post and beam or "top plate" of platform framing methods is analogously performed by the heavier top girts (wider 2x lumber) of those walls. In the technique, the girts are through-bolted by large carriage bolts, and both an inner and outer girt are generally used to support the roof loading, which is frequently a truss roof supporting purlins, not stick built ridge board and rafter construction using rafters. When used, some rafters may be attached directly to the poles. Purlins might also be used when rafters are spaced farther apart, for in either case, purlins are like girts, oriented at right angles to the truss or rafters they cross, as well as the long sheet like metal roofing elements commonly used in roofing and siding Pole buildings.
The posts provide a strong vertical anchors and supports for attaching the shell of the building which is connected by bolted through girts running ribbon like horizontally like bands at different heights generally about two feet apart. The posts replace the studs commonly used in the more familiar platform framing construction techniques people see in housing. The exterior walls are indirectly attached to the outer edge of the posts onto girts which run around the building like wooden bands at the same fixed heights about two feet apart from where the upper girts support the roof and rafters at intervals about 2 feet on center to a bottom girt that is possibly under the sub-floor level supporting the rafters of a wooden floor. The roof is attached to the top girts (normally both) of the longer wall usually via a standard ridge beam and rafter or more commonly, using a truss system which can span longer distances and requires no interior posts and beams with modern tech.
The techniques originated in the, which was a quick and economical method of adding outbuildings on a farm as agriculture shifted to equipment dependent and capital intensive agriculture—necessitating sheltering tractors, harvesters, wagons and the like in much greater quantities and sizes. Around North America, many pole built structures are still readily seen in rural and industrial areas, for the galvanized steel siding and roofing of the thirties has proven to be very durable as was much of the shed style vertically oriented plank siding.
The walls of a pole building are normally built using 6×8 or 6×6 pressure treated posts. For a standard snow load of 40 to 50 pounds, the posts are spaced evenly from 8' to 12' apart down both sidewalls. Posts on the end walls are normally spaced to allow for doors and provide framing for the walls. The walls are connected using a girt system of 2×6 dimensional lumber normally spaced 24" apart up the outside of the posts connecting them together. Other girt systems include framing in between the posts rather than on the outer side of the posts.
Siding materials for a pole building are most commonly rolled-rib 29-gauge enameled metal cut to length in 32" or 36" widths attached using color-matched screws with rubber washers to seal the holes. However, any standard siding can be used, including T1-11, vinyl, lap siding, cedar, and even brick. Using sidings other than metal may require first installing sheeting, such as CDX, OSB, or Plywood.
In modern developments the Pole Barns of the 30s have become "Pole Buildings" under the influence of new building materials such as inexpensive metal roof and siding products in stylish varieties and so today serve a more general purpose, such as housing, commercial use, or storage. In the process more often than not, the poles have become posts of squared off pressure treated timbers. These structures have the potential to replicate the functionality of other buildings, but they are more affordable and require less time to construct. The most common use for pole buildings is storage as it was on the farms, but today it is of automobiles or boats along with many other household items that would normally be found in a residential garage, or commercially as the surroundings for a light industry or small corporate offices with attached shops. The reason these buildings are so affordable is because they use a technique called Pole Framing.
When center posts are tolerable a more economic technique uses shed roofing and standard rafters being supported from the row of center posts (higher than wall end posts) that are necessary with ridge and rafter roof framing which needs building support near the centerline, but the ability to have two girts supporting the ends of the rafter below and slightly outside of the ridge board simplifies its construction and strengthens the roof. Further, extending that configuration by adding an intermediate row of poles collinear in height along the line lying between the height of the center and wall posts can be used to hang girts in the same plane as the line from the ridge board to the wall top girts. This in effect allows the building to use the same length rafter elements from post row to post row repeated as needed 'nn times' and extend such a roof a significantly allowing a deep building with a roof with many sub-structural elements all providing the same pitch.
- National Frame Builders Association
- Quality Steel Buildings, Inc. - What is a pole building?
- Pole Building Glossary. Terminology - Pole Buildings, Retrieved 28 April 2010.