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Purchasing A Metal Building System? Here’s What You Need To Know!

So you’ve decided that you need a new metal building system. Or maybe you want to expand the building you already have. One of the first things you will need to determine is how to describe your new building when communicating with your metal building supplier. The first article in this series of articles focuses on selecting your metal building supplier. The next several articles will address how to confidently and accurately describe your metal building.

Width, Length & Eave Height of Metal Building: Width, length and eave height are the most basic descriptions of a metal building. Let’s start by defining what these terms mean in the metal building industry.

Width is the building dimension measured from sidewall to sidewall.endwall

  sidewall Length is the dimension measured from endwall to endwall. The sidewall is the wall on which gutters are installed. Remember that in the metal building industry the width of the building is always stated first. For example, a 30 ft. wide x 40 ft. long building is referred to as a “30 by 40.”

eave-heightEave height is the vertical dimension measured from floor to eave.
Now we have width, length and eave height covered, let’s address a few more key terms you need to be familiar with.


Roof Slope:  The roof slope is simply the change in elevation from the eave of the building to the peak. The industry standard in the southern United States has long been a 1:12 roof slope. That means the roof rises (or falls) 1 inch for every 12 inches you move along the width of the building. roof-shape Roof slopes may begin to get slightly steeper as energy codes begin to be enforced, but that is a topic for a future discussion. Suffice it to say that the main reasons to change from a 1:12 roof slope in the southern United States are for aesthetics or to obtain specific clearances in the endwall or inside the building.

Column Shape: constant-tappered The two most common rigid frame column shapes are tapered and constant depth. As you can see, a constant depth column has the same depth from top of the column to the bottom. A tapered column tapers from its narrowest point at the floor to the thickest point at the connection to the rafter. A tapered column will usually be lighter, and therefore less expensive, than a constant depth column after a building exceeds about 40 ft. in width. There are reasons to select a constant depth column even though it may be more expensive. One example would be accommodating drywall framing. The drywall studs will install more easily around a constant depth column than a tapered column. Being able to recognize these two different rigid frame column shapes will be helpful in your purchasing process. However, in the absence of a specific need, the metal building supplier will not expect you to specify a particular column shape. You can simply allow the metal building supplier to quote you the most economical rigid frame column shape for your project.

Sidewall Girt Type: flush-bypass-girt The two most common sidewall girt types are flush and bypass. With a flush girt system, the outside flange of the girt aligns with the outside flange of the rigid frame column. In contrast, the entire girt is installed outside of the rigid frame column with a bypass girt system. The advantage of the flush girt system is that it maximizes the usable floor space in the metal building. The advantage of the bypass girt system is that, as bay spacing increases to 25 ft. and beyond, the girts are lighter and therefore less expensive than girts in a flush girt system. The reason for this is that bypass girts overlap at the rigid frame column connection providing for additional support. Similar to the column shapes, unless you have a specific need for a particular girt system, it may be best to allow the metal building supplier to utilize the most economical system for your project.

Sidewall Bay Spacing:  Sidewall bay spacing is the dimension from the center of a main frame column to the center of the next main frame column. The most common sidewall bay spacing ranges between 20 and 25 feet. However, bay spacings less than 20 feet and greater than 25 feet are also easily achievable. Your metal building supplier will typically determine the most economical sidewall bay spacing for your building.

Endwall Frame Type:  The two most basic categories of endwall frames are expandable and nonexpandable. Metal building manufacturers use different terms for these types of frames but they will all understand what you mean if you use the terms expandable and nonexpandable. ridgid-frame-endwall The primary reason to use an expandable frame at the endwall is to allow for easier expansion in the near future. An expandable endwall frame is designed to perform the same as an interior main frame. This allows you to easily expand your building lengthwise by first removing wall panels, girts and sheeting columns. As you might guess, an expandable endwall is heavier than a nonexpandable endwall and therefore costs more. bearing-endwall-frame In the nonexpandable category, there are two options – bearing or half-load rigid frame. The advantage of the bearing frame is that it is usually the least expensive endwall frame type. A half-load endwall frame looks like an expandable endwall frame but it is not the same. The half-load rigid frame endwall is lighter because it is not designed to carry as much load as an expandable frame (thus the name “half-load”). Like the bearing frame, the half-load rigid frame is not expandable. The advantage the half-load rigid frame has over the bearing frame endwall is that the half-load rigid frame eliminates the need for X-bracing in the endwall.

Base Condition:  Base condition refers to the type of component to which the base of your wall panel is attached. The components usually used to support the base of wall panels are base angle, base channel or base girt. The base angle is the least expensive option of the three. If you are planning to install an interior liner panel in your building, you will need a base channel. base-condition

Primer:  Primer refers to the coating that is applied to the un-coated steel in the manufacturer’s fabrication plant. Most metal building manufacturers use a “red-oxide” color primer with grey being the second most popular color. It is important to keep in mind that the coat of shop primer is intended to protect the steel framing for only a short period of exposure to ordinary atmospheric conditions. Therefore, you want your building to be installed soon after delivery. If you want a more long-term finish on your steel, you should consider a galvanized finish. A galvanized finish is more expensive than a shop coat of primer but it is also much more durable. That wraps up the building information portion about describing your metal building system. In the next article we will dig a bit deeper and cover design information.

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