What is a rigid frame in a metal building?

A rigid frame is the primary structural system of a pre-engineered metal building: a pair of columns and rafters joined into one moment-resisting unit, usually web-tapered so the member is deepest at the haunch where the bending moment is greatest. It carries the building without needing interior columns, which is why it can clear span.

How far can a rigid frame clear span?

Standard single-span rigid frames reach about 150 ft without interior columns. Custom engineering extends that to roughly 300 ft, which is the widest single span most manufacturers will quote.

Is a rigid frame building cheaper than a modular frame?

Below about 80 ft of width they cost roughly the same. Above it, modular framing with interior columns gets progressively cheaper, and past 150 ft it typically runs around 14 percent less on the building package. Clear span above that width is bought for what it makes possible, not for economy.

Rigid frame, priced honestly

“Rigid frame” is the industry's own name for the primary framing of a pre-engineered metal building — the tapered column-and-rafter assembly that lets a building clear span. This site covers the decisions that set what one costs, with the numbers shown rather than gated behind a form.

Recommended configuration

Modular frame

120 ft sits in the crossover band where the two diverge — modular should come in around 9% lower.
The gap is small enough here that a single column in the wrong place can erase it. Price both.

Framing steel

6.00 – 8.36 lb/sf

72 – 100 tons total

Package

$18.71 – $23.91/sf

$449K – $574K

Installed

$29.00 – $45.43/sf

$696K – $1.09M

Planning-stage estimate calibrated to published industry ranges. Not a substitute for a stamped design by a licensed engineer.

Open the full selector Price a clear span

What a rigid frame actually is

A rigid frame is a column-and-rafter pair joined into a single moment-resisting unit. Because the joint at the knee transfers moment rather than just shear, the frame stands on its own and needs nothing inside the building to hold the roof up. That is the whole trick, and it is why a metal building can be column-free across widths that would need a forest of posts in any other system.

The members are usually web-tapered: deep where the bending moment is largest, at the haunch, and shallow where it is smallest, at the base and the ridge. That wedge profile is not styling. It is the frame following its own moment diagram, and it is the reason a rigid frame is the lightest practical way to cover a wide bay.

Everything else about the building — purlins, girts, bracing, panels — is secondary, in the literal industry sense. The rigid frame is the primary framing, and it is where the money and the engineering are.

Cost by span, at a glance

Baseline case: clear span, 20 ft eave, 25 ft bays, 20 psf ground snow, 115 mph wind, no crane. The pattern to notice is that the steel column does not rise in a straight line.

Clear span rigid frame, baseline case
Span	Steel lb/sf	Package $/sf	Notes
40 ft	2.20–3.20	$14–17	Light frames. Span is rarely the cost driver at this width - eave height and snow load matter more.
50 ft	2.60–3.60	$14–18	Still comfortably inside standard shipping and erection practice.
60 ft	3.00–4.20	$15–18	The practical floor for commercial work. Below this width, small-building suppliers price better.
80 ft	3.80–5.20	$16–20	The crossover band. Clear span and modular start to diverge in cost here - price both.
100 ft	4.60–6.40	$17–21	Haunch depth begins to govern interior clearance. Check usable height, not just the eave.
120 ft	5.60–7.80	$18–23	Deep haunches and heavier anchor-bolt patterns. Foundation cost stops being a rounding error.
150 ft	7.00–9.80	$20–26	The practical ceiling for a standard single-span rigid frame. Past this you are buying custom engineering.
200 ft	9.50–13.50	$24–32	Custom engineering, shipping splices, and heavier erection equipment. Modular usually wins on cost alone.
250 ft	12.50–17.50	$28–38	Specialist territory. Justified by use, not economics - hangars, arenas, column-free process floors.
300 ft	16.00–23.00	$33–46	The upper limit most manufacturers offer. Expect a bespoke frame design and a long lead time.

Planning-stage estimate calibrated to published industry ranges. Not a substitute for a stamped design by a licensed engineer. How these figures were derived.

The seven frame configurations

Clear Span

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.

Modular

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.

Single Slope

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.

Lean-To

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.

Multi-Gable

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.

Tapered Column

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.

Straight Column

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.

Rigid frame, priced honestly

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