A metal pole barn is a structure designed for storage of materials or machinery that is made of metal, usually steel or aluminum. The structure features a roof that is supported by a number of poles that make up the perimeter of the structure, and in many cases, the structure features no walls. Walls can be added to the metal pole barn, but they are not load-bearing elements and are therefore not necessary on some structures. To choose the best barn for you, it helps to first decide what you will use the structure for.
Most metal pole barn structures are rectangular, though some may be square, while others may feature a more elaborate design. Simplicity usually translates into lower cost and added functionality, but a metal pole barn can be built to accommodate specialty functions. If you will be storing a car or truck in the metal pole barn, you may only need a small rectangular structure; it may or may not feature walls, depending on how safely you want to protect the vehicle. If, however, you will be housing livestock, a larger rectangular pole barn with walls may be necessary.
The floor of the metal pole barn may be concrete or bare earth. Choose between the two by deciding what you will store within: if you will be storing heavy machinery, consider a concrete floor. If you will be storing hay, dirt, or other materials, you may not need anything more than a dirt floor. Livestock storage may also only require a dirt floor, though some farmers do decide to make a concrete floor for ease of cleaning and stability of the floor structure.
The metal used to make a metal pole barn can vary, though steel and aluminum are the most common materials. Smaller structures may be made of aluminum, though larger structures are likely to be made of steel. Any structural elements, such as the poles themselves, should be made from steel for added stability and durability. Aluminum is often appropriate for roofing materials or for constructing non-load bearing walls. Light-duty structures, such as those used to house a single vehicle, may be made entirely from aluminum, which will not corrode and is lightweight and easy to work with. It is not, however, the strongest metal, and it can bend or break fairly easily; thicker gauge steel will not bend or break as easily, and it will be able to support more weight.