Construction is a complex process with so many moving parts it’s hard to believe there’s any rhyme or reason to it. Prefabricated steel buildings simplify some of that process because they are manufactured off-site in rigorously controlled conditions and stringent quality assurance requirements.
Building manufacturers check for fit by assembling the components in-house before shipping them, ensuring that the building system the customer receives meets or exceeds every quality metric.
Here is an overview of the various components that go into fabricating and assembling a steel building.
The primary frame of a steel building consists of the beams and columns that create the skeleton of the structure. It provides the framework for the type, style, and shape of building to come and a building is only as strong as its frame. Most manufacturers offer standard framing options as well as design services for entirely custom-built structures.
- Welded Rigid Frame (WRF) consists of tapered members and provides the strength for the widest possible spans without the obstruction of interior columns.
- Lean-To (LT) is a structure attached to one wall of an existing building. It is an economical solution for creating additional office space, storage or other needs. Because the frame design creates minimal horizontal thrust, the foundation costs are minimized.
- Column and Beam (CB) is used to build wide buildings with internal columns. This design is also called a modular framework and can be used with bar joist roof or zee shaped purlins.
- Single Slope Welded Rigid Frame (SSRF) is a layout best used for areas where drainage restrictions are an issue, such as in a strip shopping center. The single slope comes with straight columns and interior columns.
- Welded Tapered Beam (WTB) maximizes floor space with straight sidewalls. Installing interior finishes is an easy task, and you save money on the foundation because the horizontal frame base reaction is minimized.
I-beam style frames are the most common primary frame design, but tapered beam provides strength in open span construction. Another design that lends itself well to very large span spaces is the open web design, which is a top and bottom chord connected with diagonal angles. Open webs are also known as trussing.
The primary framing system includes the columns and beams for the walls and the rafters for the roof. Once complete, the primary frame indicates the approximate look the completed building will take.
The secondary framing provides the components to which the metal wall panels will be attached. It also includes framed openings such as those for doors and windows.
Secondary framing consists of eave struts, girts and purlins. These secondary frame members are typically Z and C shaped (and occasionally U-shaped) depending on the roof system and your budget. Most are made of cold-formed steel.
- Girts are the spanning members for the wall panels and provide additional strength, stability and vertical load support. They can be inset or flush mounted with the column on the end wall while on the side walls they can be outset or bypass installations. Girts are also used when installing wall cladding.
- Purlins provide the same connection as girts but are specialized for roof panels and systems. Purlins are the spanning members used to support the roof deck and enhance the strength and rigidity of the roof. They add mid-span support and allow for wider roofs.
- Eave struts join the roof and the exterior wall and act as the first roof purlin or final and highest wall girt. The top flange supports the roof while the web supports the wall.
The primary and secondary steel framing systems work together to provide all the strength your building requires to meet code and its intended use. Steel can bend rather than shatter or break under stress and reduces the chances of a catastrophic building failure.
All cutting and drilling for framing will take place at the manufacturer to maintain standardization and quality of fit. You only need to put the building together with the fasteners included in the kit.
- Each nut and bolt, a screw, or another type of fastener has a place in the predrilled holes of the frame.
- Screws with neoprene washers are used to attach panels to the building. These screws are known as “self-drilling” and drill their own hole in the girt or purlin to attach the panel. The neoprene washer keeps the hole sealed once the building is together.
- Make sure the fasteners you order or receive match the quality of the rest of the metal in your building system.
Just as high-quality steel makes the strongest buildings, only the highest quality fasteners will keep the panels from flying off the building in high winds and seal it against moisture.
Additional bracing may be required to meet higher than normal wind loads or seismic loads. Most bracing will create a diaphragm but can be supplemented with rod (or X-bracing), angle or cable bracing if the diaphragm capacity is not adequate.
X-bracing can be replaced by cantilever columns or portal frames.
The word “accessory” sounds like something that is optional, but in the case of a steel building, it refers to the windows, doors and items to fill other penetrations or openings. Roof vents and skylights also fall into this category.
The type of door you select depends on how the building will be used. You can have a walk door installed for personnel to use. Larger doors are available for airplane hangars, agricultural, warehouse or manufacturing buildings. There are different types of large doors available, both overhead and sliding.
- One type of overhead door is a roll-up, so-called because the door is made of narrow horizontal panels that roll up like a shade.
- Other overhead doors come in larger sections and look like a typical garage door.
- A sliding door, depending on the size, may have wheels on the bottom of the panel.
- Electric motors can be installed to push a sliding door along its track or lift overhead doors.
Every building component you select should be the right one for the job. Once you have designed your building according to local codes, you will have a better idea of the shapes and sizes of the various parts of the primary and secondary frame.
The final components included in your steel building system are roof and wall panels, which come in a variety of stock colors or you can select a custom color. The manufacturer bundles the panels to eliminate the potential for damage. Also made of high-quality steel, your panels keep out the wind, rain and pests while keeping the interior environment safe and comfortable.
Before selecting any metal building component, finalize your design and jobsite location so you can make the best choice of frame and accessories.