Hoping to save money on a new Becker County Highway Department facility, made of precast concrete and estimated to cost about $8 million, commissioners are exploring other types of buildings.
They are considering options including precast concrete, steel, and pole barn, and will tour facilities in the area made of those materials.
The firm working on the project, Oertel Architects of St. Paul, said in a report that any type of material could essentially be made to work, but a pole barn-type building would have to include steel in places to support a 5-ton crane in the maintenance area, for example.
A less-expensive pole barn building also comes with a much shorter projected lifespan, and generally brings more problems with leaks and maintenance, unless a better grade of roof is used.
Here are the options the board is considering:
• A precast building is a heavy industrial-type structure with a precast concrete shell and steel or precast concrete roof. The walls are concrete inside and out. They usually have flat roofs and internal storm drains. Their life span is set at 50-100 years, depending on good maintenance.
• A steel building is an all-purpose and cost-effective structure, usually pre-engineered and partially designed by the contractor. It's made with a kit of standard parts using a steel frame, steel structure and steel skin at the walls and roof, which is a low-pitched gable. Interior wall materials vary, and there is a range in roof quality and cost. Its lifespan is projected at 25-50 years, depending on maintenance and other factors.
• A pole barn is considered an agricultural type building in the industry, and is also referred to as timber frame. This is essentially like building a structure like an old-fashioned barn, with large timber columns and frames. It is typically made without a perimeter foundation.The wood frame structure is typically covered with a metal skin and the low-gable roof type is typically of metal. Its lifespan is projected at 15-30 years, depending on maintenance and other factors.
One way to meet the highway department needs and still meet code using pole barn construction would be to build three or four separate buildings, or build one building at different heights for vehicle maintenance, vehicle washing/storage, and office space, Oertel reported.
There are problems with using steel or metal construction for public works buildings. For example, the corrosive nature of the salt-sand mix and other chemicals means that extra protection is needed for metal siding and liner panels for the building to last.
The standard roof used in pole barns would need to be upgraded for a public works facility. A pole barn, or metal material in general, won't work well for a wash bay, since the oversprayed salt gets everywhere, into cracks, joints and behind walls, and rusts out the bays pretty quickly.
Pole barns tend to be less energy efficient over time.
Structural steel works better in a public works facility, with more salt and moisture in the air than usual, since these are made of heavy steel, just like a steel bridge. It is the less substantive metal materials that are a concern. A pole barn uses thin steel gusset plates and there is not much material to last over time if corrosion is present. Metal panels commonly used in pole barn buildings are also easily marred or tented by heavy duty operations.
However it's constructed, the new public works building will need the same mechanical, plumbing and electrical systems, floor loading, earthwork and mechanical systems, Oertel said. Costs can vary, but all of that might add up to perhaps 60 percent of construction costs, with the actual building structural shell 20 to 25 percent of the total project cost. So cost savings from a cheaper type of building might not be all that commissioners might hope for, compared to the long-term drawbacks.
"More could be said about the differences between pole barn construction and a more heavy duty construction using precast concrete," the report sums up. "It mostly comes down to a lower front-end cost with a pole barn, at the sacrifice of longevity..."