Construction Concerns: Pole Buildings

By Gregory Havel

Pole buildings are common in suburban and rural areas. Small versions are most common in suburban areas and are often used for storage, garages, and hobby shops as well as for barns on hobby farms. Larger versions are more common in rural areas and are used for storing machinery, as repair shops, and for housing farm animals.

A pole building can be as wide as a truss can span, and can measure hundreds of feet long.

Photo 1 shows a small pole building under construction in a subdivision in a rural area. The poles were set in holes bored into the ground by machine, braced in line, and plumb with the holes filled with concrete. Permanent horizontal bracing (girts) were nailed to the posts. Wood roof trusses were set on top of the poles and permanently braced with purlins running perpendicular to the top chords of the trusses.

(1) Photos by author.

 

Photo 2 shows the same building with the metal roof in place screwed to the top of the purlins. The open space at the peak of the roof will be covered with a ridge vent, which will allow air movement but also keep out rain and snow. In the right foreground, temporary bracing of a pole is visible as well as the ends of girts and permanent bracing between the trusses.

(2)

 

Photo 3 shows the same building with metal wall panels screwed in place to the girts. This building will have two large overhead doors plus a single service door out of the photo to the right.

(3)

 

Pole buildings start with a gravel floor; many have a poured concrete floor. They usually have electricity and may be insulated or uninsulated, heated or unheated, exposed framing on the inside or finished interior walls, and may or may not have plumbing.

On completion—inside and out—these structures are used as office buildings, factories, fire stations, vehicle repair, and even churches. After completion this building type may be difficult to distinguish if it is a wood frame or of engineered steel structure.

The ridge vent has enough capacity to prevent condensation from forming inside the open building or its attic space if the interior is finished, but it has little capacity for venting the products of combustion if a fire erupts in the interior. The roof is strong enough to keep out the weather, but it may not have enough strength to support firefighters during roof ventilation. The truss span will usually be too long for proper use of a roof ladder.

If the building’s interior is completed, the arrangement of girts attached to the—inside and out—will create a set of interconnected concealed spaces between the inner and outer wall panels which will also be connected to the attic (truss) space. A fire in the concealed space will behave similarly to one in balloon-frame construction.

Buildings like this do not often have an automatic fire sprinkler system. They may be used for storage on a farm with limited water supply or in a more urban area where the developer may have kept the building small enough so sprinklers are not required.

If a fire starts inside one of these buildings, venting the gables may be your only option since you cannot depend on the roof to support vertical ventilation.

In rural areas and in neighborhoods with long response times, structural collapse may happen by the time a fire department arrives.

This type of construction can be extremely hazardous to firefighters because of the possibility of early collapse and because of the sharp-edged metal panels that may fall. This type of construction deserves a note in your preincident plans.

Download this article as a PDF HERE.

 

Gregory Havel is a member of the Town of Burlington (WI) Fire Department, a retired deputy chief and training officer, and a 35-year veteran of the fire service. He is a Wisconsin-certified fire instructor II, fire officer II, and fire inspector; an adjunct instructor in fire service programs at Gateway Technical College; and safety director for Scherrer Construction Co., Inc. Havel has a bachelor's degree from St. Norbert College with more than 35 years of experience in facilities management and building construction. He has presented classes at FDIC.

 

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