If you are contemplating purchasing a prefabricated steel building, you might be wondering what you receive as part of the standard metal building. Details may differ from vendor to vendor, but here is a discussion of components that are included in the price of the kit.
One of the benefits of buying a premanufactured steel building is that the components are prefabricated, cut, welded, and drilled at the manufacturer for easy, on-site assembly. Depending on the complexity of the building, some of the components may arrive preassembled.
Primary framing elements
The primary framing elements, the columns and rafters, comprise the rigid steel frame for your structure. How many primary members you receive depends on the size and type of building you are erecting.
Clear span buildings provide open center spaces without interior columns. Clear span buildings range from small in size, such as a garage, to larger sizes that can accommodate a sports arena. Larger buildings require sturdier primary members than smaller ones. Computerized software is used for calculations for load design as the final determination on the composition and size of the primary members.
A building that has interior columns is an option when you don’t require open center space. Many industrial facilities and manufacturing spaces use this design. The interior columns and rafters are commonly made of a lighter material, which saves on cost.
The primary frame members are marked for identification and come with pre-welded clips to simplify assembly.
Secondary framing elements
Girts, purlins, and eave struts are all components of your structure’s secondary framing. Secondary framing members go from 12 gauge to 16 gauge rolled steel and contribute to the stability of the structure. They are fastened to the primary frame by clips pre-welded to the primary members.
- Girts attached to the wall and primary frame columns help stabilize the primary frame columns to provide shear resistance and attachment framing for wall cladding. The girts are stabilized by rods, angles, and straps as well as by the wall cladding.
- Purlins span from rafter to rafter parallel to the building eave. The purlins function much the same as the wall girts to help stabilize the building frames and to provide the attachment framing for the roof cladding.
- Eave struts are located at the intersection of the exterior wall and the roof to act as the first purlin and last girt.
A building’s eave height is measured at the top of the eave strut to the base plate of the primary wall column.
If needed, your building kit will contain rod or cable bracing to add rigidity. The rods or cables are inserted diagonally to create an “X” shape from the eave strut to the wall columns or the rafters that define the length of a bay or other section of the structure.
Wall and roof panels
Sometimes called sheeting, steel panels are attached to the girts and purlins to enclose the space. While all steel primary and secondary members are coated for protection with a primer or Galvanizing, the metal wall and roof panels can be coated in a variety of colors and textures.
- Exposed fastener metal roof and wall panels are cost efficient options for a basic building. The panels lap over each other and are fastened to the structure using self-drilling fasteners that penetrate through the field of the panel into the structure below.
- Standing seam roof panels have few if any exposed fasteners which make them more water tight than exposed fastener roofs.
- Many roof panels can be coated in patterns replicating shingles, tile, and other types of roofing material.
- Architectural panels have different designs worked into them to create different looks for the walls of your building.
Most vendors keep certain panel colors in stock while others must be custom-ordered.
Door and window framing
The openings in your building require framing and trim to seal out moisture and maintain the interior environment. A steel building kit contains the materials for all of the framed openings for doors and windows.
Depending on the building’s use, you may receive framing for a personnel door or a much larger opening for a roll-up or overhead door. The doors themselves are considered accessories and may not be part of the standard kit.
Everything you need to fasten the frame and panels are part of the standard building kit. Bolt holes are predrilled in the factory so all you need to do is match them up and place the fastener. You will also receive washers, nuts, and clips if they are required.
Another type of fastener you may receive include self-drilling fasteners, which combine a drill bit and a fastener. The self-drilling fastener is designed to drill and tap its own hole in the light gauge steel girts and purlins. The self-drilling fasteners are made from the same rust resistant steel as the panels.
Additional flashings and sealants are needed to provide a weather tight roofing and wall system.
Ridge cap and base angle
The ridge cap matches the slope and contours of your roof and tightly seals the roof ridge. The cap ensures metal to metal contact to improve the seal and keep pests out.
The base angle is the connection between the wall panels and the foundation used to seal the base of the building from moisture and pests while maintaining the indoor environment.
Drawings and anchor bolt plan
You will receive one or more copies of the engineering drawings for your building, stamped and certified for construction. Along with these plans you will receive detailed erection instructions including lists of required tools.
An anchor bolt plan is included to provide a placement pattern for the foundation engineer. Anchor bolts securely fasten your building to the foundation but require optimal placement that matches the design of the structure.
Anchor bolts are not usually included in the building kit but can be sourced from a local vendor.
When you purchase a prefabricated steel building, the vendor includes everything you need to assemble the building from the frame to the fasteners. You also receive instructions and certified, stamped drawings that adhere to the local building code where your structure is sited.
All you need to bring are a few tools, some experienced help, and you are ready to erect the steel building of your dreams.