Frame type
The wedge profile of a metal building column is not styling. It is the member following its own moment diagram — shallow where the bending is small, deep where it peaks. Web-tapered members are why a rigid frame is the lightest practical way to cover a wide bay, and they are the standard configuration for anything clear span.
Practical span range
40–300 ft
Where this configuration is normally used
Built-up members whose web depth follows the moment diagram - shallow at the base, deep at the haunch. The standard configuration for clear span, and the reason a rigid frame is the lightest way to cover a wide bay.
Skip it when: Interior walls, racking, or liner panel need a flat column face for their full height.
A rigid frame column carries almost no moment at the base, where a pinned connection lets it rotate, and a great deal at the knee, where it meets the rafter. A constant-depth member has to be sized for the worst point along its length and then carries that depth everywhere, including where nothing needs it.
A built-up tapered member does not. The web is cut to a taper and welded between flanges, so depth grows from base to haunch in step with demand. Nothing is deeper than it needs to be, and the steel that would have been dead weight is simply absent. On a wide frame that is a large fraction of the primary framing weight.
It is also why these are built-up plate members rather than rolled shapes. A rolled beam comes in fixed depths and constant section; a plate girder can be any depth at any point along its length. The whole PEMB industry is built on that freedom, and the tapered column is its clearest expression.
Tapered is the cheaper option, and by enough that it is the default at any span above about 60 ft. Below that the weight penalty for a constant-depth column is small enough that the frame selector recommends a straight column instead, because simpler sidewall framing is worth more than the steel saved.
The saving grows with span, for the same reason everything else in this section does: moment grows with the square of the span, so the difference between following the moment diagram and ignoring it grows with it too.
What the taper costs is not money — it is a flat interior face. If racking, liner panel, masonry wainscot or a full-height partition needs to sit against the column for its full height, a tapered column will not give it to them, and buying a straight column instead is a usability premium you pay deliberately.
Planning-stage estimate calibrated to published industry ranges. Not a substitute for a stamped design by a licensed engineer. How the figures behind those percentages were derived.
The widths this configuration reaches that have a page of their own, with what a clear span at that width costs and what a column line would save against it. Where the saving is meaningful, that number is the case for or against this configuration in one figure.
| Width | Clear span steel | Clear span package | Modular saves | What changes at this width |
|---|---|---|---|---|
| 40 ft | 2.04 – 2.97 lb/sf | $13.45 – $16.33/sf | — | Light frames. Span is rarely the cost driver at this width - eave height and snow load matter more. |
| 60 ft | 3.00 – 4.20 lb/sf | $15.00 – $18.00/sf | — | The practical floor for commercial work. Below this width, small-building suppliers price better. |
| 80 ft | 4.07 – 5.57 lb/sf | $16.63 – $20.79/sf | — | The crossover band. Clear span and modular start to diverge in cost here - price both. |
| 100 ft | 5.26 – 7.32 lb/sf | $18.35 – $22.66/sf | 5% | Haunch depth begins to govern interior clearance. Check usable height, not just the eave. |
| 120 ft | 6.41 – 8.92 lb/sf | $19.43 – $24.82/sf | 9% | Deep haunches and heavier anchor-bolt patterns. Foundation cost stops being a rounding error. |
| 150 ft | 8.26 – 11.56 lb/sf | $21.98 – $28.57/sf | 14% | The practical ceiling for a standard single-span rigid frame. Past this you are buying custom engineering. |
| 200 ft | 11.55 – 16.42 lb/sf | $26.85 – $35.80/sf | 22% | Custom engineering, shipping splices, and heavier erection equipment. Modular usually wins on cost alone. |
| 250 ft | 16.10 – 22.54 lb/sf | $32.44 – $44.02/sf | 28% | Specialist territory. Justified by use, not economics - hangars, arenas, column-free process floors. |
| 300 ft | 21.76 – 31.28 lb/sf | $39.53 – $55.11/sf | 33% | The upper limit most manufacturers offer. Expect a bespoke frame design and a long lead time. |
Each row is priced at the case on that width's own page — the eave and length that actually get built there — so the rows are comparable to those pages rather than to each other. Planning-stage estimate calibrated to published industry ranges. Not a substitute for a stamped design by a licensed engineer.
A single rigid frame carrying the full width with no interior columns. Maximum usable floor area and total layout flexibility, paid for in steel weight that rises faster than the span.
20–300 ft →One or more interior column lines split the width into modules, so each rafter spans only a fraction of the building. The savings grow with width and become decisive past roughly 150 ft.
60–480 ft →One continuous slope from a high eave to a low eave, with no ridge. Drains to one side, presents a taller street face, and fits sites where a gable would break a height limit.
20–200 ft →A single-slope module framed off an existing sidewall, with no independent ridge. The cheapest square footage on any project, provided the host frame can take the added load.
10–60 ft →Two or more gable modules side by side sharing interior columns, covering great width with short, cheap spans. The tradeoff is a valley - an interior gutter line you must detail and maintain.
80–600 ft →Constant-depth columns. Heavier than a tapered equivalent, but they give a flat plane for racking, liner panel, masonry wainscot, and interior partitions, and they simplify sidewall framing.
20–150 ft →Not sure which one you need? The frame selector takes width, eave height, crane load and whether a column can stand inside, and tells you which configuration fits — and what the runner-up would have cost. Or go straight to quotes.