Glossary
The quote, translated
Twelve terms that decide what you are actually buying, defined the way the people who engineer these buildings use them.
Configure a building and see these terms used in anger.
The twelve terms worth knowing
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What is red iron?
The trade name for hot-rolled structural steel framing, after the red-oxide primer the members wear out of the shop. When a quote says red iron it means an engineered rigid-frame system with primary members of grade structural steel, as opposed to light-gauge cold-formed or tube framing.
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What is a clear span?
The width a building covers with no interior columns. A 60-foot clear span means sixty feet of open floor under one frame. Clear span is the single most expensive dimension to grow, because the rafters carry the whole width themselves.
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What is a rigid frame?
The primary structural unit of these buildings: columns and rafters joined with moment connections so the assembly resists loads as one bent. A building amounts to a row of rigid frames with everything else spanning between them.
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What is a built-up tapered member?
A column or rafter welded from steel plate into an I-shape whose depth changes along its length: deep where bending forces peak, shallow where they ease. Tapering puts steel only where the loads are, which is much of why engineered frames compete on cost.
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What are purlins and girts?
The secondary members. Purlins run across the roof from frame to frame and carry the roof panel; girts do the same job on the walls. They are typically cold-formed Z or C profiles from galvanized coil, and they are what the panel screws bite into.
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What is PBR panel?
The workhorse ribbed steel panel of the industry; the letters stand for purlin-bearing rib. Its shape lets the panel seat directly on purlins and girts and lap its neighbor cleanly, which is why most quotes assume it for both walls and roof.
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What does gauge mean on a panel?
Sheet thickness, on a scale where smaller numbers mean thicker steel: 24-gauge panel is heavier than 26-gauge. A quote naming its panel gauge is telling you something checkable about the envelope; a quote that omits it is worth a question.
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What is collateral load?
Everything the structure carries beyond its own weight and the weather: insulation, liner panel, lighting, sprinklers, mechanical, mezzanines, hoists. It is declared during design, in pounds per square foot or as specific loads, and it changes member sizes. Forgetting a future load here is the classic expensive mistake.
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What is an exposure category?
A wind-design input describing the terrain around the site. Sheltered suburban ground and open country push different wind pressures onto the same building, so the category shifts the loads the frame is engineered for. It appears in any proposal that states its design loads.
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What are erection drawings?
The drawing set the building is assembled and permitted from: framing plans, member marks, connection details, sequence. This is the document set a customer actually receives; the shop's own fabrication drawings stay internal, and a seller promising those is describing paperwork the industry does not hand over.
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What are design calculations?
The engineer's math behind the drawings: load derivations, member checks, connection capacities. Some permit offices require them alongside the drawings, which is why suppliers provide them on request rather than by default.
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What does pre-engineered mean, in one sentence?
Engineered before fabricated: the structure is designed to one site's loads and one owner's use, then manufactured as a bolt-together kit, which is the entire idea the rest of this glossary hangs off.
Take the vocabulary shopping
Every line on a quote now means something. Get one engineered to your site and read it with new eyes.