The Different Components Used In a Steel Building

A large number of parts go into any building to make sure it is structurally sound and resistant to wind, weather and wear. Metal buildings use largely prefabricated components that can be assembled very easily and quickly. Anyone who is interested in a steel building should understand the different components used in the structure.

Girts and Girders

Girts are girders are the horizontal steel beams that run through a building. These beams generally run through every wall. There are usually two or more levels of girts and girders in each building depending on the size. A girder is a heavy beam that helps to distribute the weight from the vertical columns. Girts help to stabilize the building and prevent bowing. A girt is normally attached to a column that is part of a sidewall or end wall. Paneling is usually attached to girts.


The rafter is a long and heavy beam that provides the main form of support for the roof. The rafter is one of the strongest parts of the building. Most steel buildings have rafters with vertical and horizontal elements. The rafter is like a frame. The legs sit on the ground or foundation and arch upward across the roof. A building can have anywhere from one to four or more rafters.


Purlins are beams that are part of the roof system in a metal building. Purlins usually run the length of the building between opposing walls in one direction only. The main job of a purlin is to provide support for the roof panels so that they are not directly attached to rafters. Purlins also help to distribute the weight of the roof to the walls and frame of the building. Most steel structures have a large number of purlins along the roof.


The columns are the vertical beams that form the basis for the frame of the entire building in the corners. Columns are commonly seen in the front and rear walls of the building where the rafters are not providing vertical support. The columns support much of the weight of the building that is not held by the rafters. Columns come in many different lengths even within the same building because they can appear on top of doorframes and along walls with variable lengths due to the pitch of the roof.

Wall Panels and Roof Panels

The exterior of the building is made from wall panels and roof panels. These are the actual steel panels that cover the outside and protect the interior of the building. Steel panels are usually corrugated for added strength. The panels come in a wide range of sizes and thicknesses. Some can be treated to reflect sunlight. Others have insulation attached during manufacturing. Steel buildings can have both exterior and interior wall panels depending on the design. Panels can usually be replaced relatively easily if damaged.


Trim is a component that helps to improve the appearance of a building and seal gaps. Trim is usually used along corners and other areas where the panels intersect or end. A ridge cap is a piece of trim that runs along the spine of the roof panels to seal them. Most buildings have a large number of pieces of steel trim.


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