Metal Buildings 101

Metal & Steel Building Anatomy

Metal Buildings 101: The Metal Building Anatomy

It helps to know the basic terminology for steel and metal buildings so that you can convey your needs clearly and effectively to your Arco sales representative.

Arco steel or metal buildings have three basic dimensions: width, length, and eave height. The width is the distance from the outside of the sidewall girt on one side to the outside of the sidewall girt on the opposite side. The length is the distance from the outside of the endwall girt on one endwall to the outside of the endwall girt on the other endwall. Eave height is the distance from the bottom of the base plate to the top of the eave strut.

Most metal buildings have four outside walls. Two of these walls are called sidewalls. This is the wall where the roof meets the wall and the contact point aligns parallel with the finished floor. This wall also determines the length of the building. The other two walls, called endwalls, show a rising line where the walls meet the roof and the height of the wall changes. On a gabled building this is the wall where the peak of the roof is obvious. On a single-slope building or lean-to the endwall shows the wall sloping from a high to low side. The endwall determines the building width.

The point where the sidewalls meet the roof is called the eave. Eave trim finishes the raw edges of the panels, or one might choose to add a gutter system to catch the rain flow from the roof. Eave height is determined by measuring the distance from the bottom of the base plate to the point where the roof and sidewall intersect. It is important to keep in mind that eave height and clear height inside the building are not the same. If you have a need for specific clearance inside your building, please speak to your sales representative so that they can help you to determine the necessary eave height that you will need.
The roof pitch or roof slope is usually shown as a ratio to 12 (i.e., ½:12, 1:12, 4:12, etc.). When inches are used as a basic unit, a 2:12 roof pitch means that the roof rises 2 inches in every 12 inches measured horizontally across the width of the building from the sidewall to the peak of the building. The point where the two rising halves of the roof meet at the endwall is called the peak. If you travel along the peak of the roof from endwall to opposite endwall, this is known as the ridgeline.

EXAMPLE: If the above building is 40' wide and has a 12' eave height, the height at the peak of the roof would be 18'8" with a 4:12 pitch.

20' (to centerline) x [4"/12"] = 6'8" (of rise) + 12' eave height = 18'8"

Arco Steel Building Frame Systems

Metal Buildings 101: Arco Frame Systems

Either clear span frames or frames with interior columns are available. Widths greater than 80 feet are more economical with an interior column. Endwall frames feature a beam and column design, unlike the rigid frame design used on the interior frames of the building, for maximum cost effectiveness. Optional rigid frame endwalls for future expansion may be ordered for the endwalls. All frames are finished with a red oxide primer.

Most, but not all, sidewall columns are tapered but may be ordered straight upon request. In most cases, a tapered column is more economical.

Gabled (Clear span)

A ridged (double slope) building in which the ridge is in the center of the building. Welded plate, tapered column "clear span" system, available in 1:12 or 4:12 roof slope. Standard widths are 20′ to 120′, eave heights of 10′ to 25′, and bay heights of 20′, 25′ or 30′. Greater widths and eave heights may be achieved, but must go through Design prior to quoting.

Gabled (with interior columns)

Gabled (with interior columns) A ridged (double slope) building in which the ridge is in the center of the building. A modular, tapered column system, available in widths of 80′ to 240′, with eave heights of 12′ to 25′ and standard bay lengths of 20′, 25′ or 30′. Roof slope is 1:12. Greater building widths may utilize more than one row of interior columns to reduce cost.


A sloping roof in one plane with both high sidewall and low sidewall columns. The slope is from one wall to the opposite wall. These are typically used for strip malls/shopping centers and office complexes. Façades or parapet walls are commonly used to give the appearance that all four walls are the same height. Single-slope buildings are also used when adding on to an existing building in the event that it was not designed to carry the load of a lean-to.


Perfect for providing you with that extra storage space you need alongside your building. The Lean-to ties in at the eave of another building or below the eave and can provide a variety of uses…from just a covered area to a completely enclosed addition to your building. Available in all width extension increments for all new structures. Width and height maximum dimensions will vary according to loading requirements. Inside clearances can be specified for all frame options.

Covering & Trim Details

Metal Buildings 101: Covering and Trim Details

Arco Roof Panels are available in our standard PBR panel or one of the optional standing seam panels for architecturally critical applications.

Both panel types are available in 24 gauge or 26 gauge steel with a painted or Galvalume finish. Galvalume is a zinc and aluminum coating over the steel that offers extremely long life and weathers to a light finish.

Arco Wall Panels are available in the durable PBR-panel or the optional architectural A-panel. Specialty panels are available upon request. A choice of 16 different Siliconized Polyester colors is available for all panels. Our trim is available in matching or contrasting colors. You may order your building without wall panels in order to use brick, block, stone or other exterior finishes.

PBR Roof and Wall Panels

Arco uses a 26 gauge PBR panel for our standard roof and wall covering. An industry favorite, the PBR panel's deep ribs create an even-shadowed appearance. The panel laps are easier to align and stitch together properly, so the panels install more quickly, and the area between the major ribs is reinforced with minor ribs. On roofs, the bearing leg protects against foot-traffic damage and helps prevent the panel from "rolling" and perhaps creating leaks. The PBR panel is one of the most economical and durable covering systems available.