Tool

Which rigid frame does your building need?

Frame configuration is decided by four things: how wide the building is, whether anything can stand inside it, how high the eave has to be, and whether a crane is hanging off the structure. Enter those and this tells you which configuration fits — and what the runner-up would have cost.

Your building

Don't know your loads? The design loads lookup gives you a starting figure by metro.

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.

Columns: Tapered Column. Web-tapered members follow the moment diagram and are the lightest way to carry this span.

Also worth pricing: Clear Span.

What that building costs

Framing steel

6.00 – 8.36 lb/sf

Primary and secondary, 72 – 100 tons total

Building package

$18.71 – $23.91/sf

$449K – $574K for 24,000 sf

Installed

$29.00 – $45.43/sf

$696K – $1.09M, before interior buildout

Modular saving

9%

If a column line were allowed

At this width: Deep haunches and heavier anchor-bolt patterns. Foundation cost stops being a rounding error.

Outside the usual range. This case prices above or below the $14–22/sf band commonly quoted for metal building packages. That band describes ordinary spans and loads; long spans, tall eaves, heavy snow, and cranes legitimately leave it. Treat the number as directional and get it priced.

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

Next step

Turn these numbers into real quotes

A dealer quoting from your actual geometry and load case beats any estimator, including this one. Three of them, each carrying engineer-stamped drawings for your state, cost you nothing to ask.

Get engineered quotes for a 120 × 200 × 24 ft building

How the choice actually gets made

Most people arrive at this decision backwards, starting from a frame type they have heard of and trying to make their building fit it. The order that works is the opposite: establish what the inside of the building has to do, and the frame falls out of it.

1. Can anything stand inside?

This is the only question that can eliminate an option outright. An arena floor, a crane runway, and a hangar door opening cannot have a column in them at any price. Everywhere else, a column that lands on a rack line or a wall line is close to free — and it is the single largest lever on the cost of a wide building.

2. How wide?

Below about 80 ft, clear span and modular cost roughly the same, because the rafter was never the expensive part of a narrow building. From 80 ft the two curves separate, and past 150 ft the separation is large enough that clear span becomes a deliberate purchase rather than a default. Around 300 ft you reach the widest single span most manufacturers will quote at all.

3. How high does the eave have to be?

Eave height is the input people underestimate. It does not just add wall panel — it lengthens the column, increases the moment at the haunch, and grows the whole frame. On a crane building the eave is set by hook height plus the crane's own depth plus clearance, which is usually taller than the number the owner first quotes.

4. What is hanging off it?

A bridge crane, a mezzanine, rooftop units, a fire-suppression main, and a heavy liner panel are all loads the frame has to carry that never appear on a site plan. A crane in particular changes the frame's character: it loads the columns laterally, every cycle, for the life of the building.

The seven 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.

Skip it when: The interior can tolerate a column line and the width is over about 100 ft. You are paying a premium for clearance you do not need.

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.

Skip it when: A column would land in a traffic aisle, a crane runway, or an arena floor.

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.

Skip it when: Width is large. The high eave gets expensive fast because the whole frame grows with it.

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.

Skip it when: The host building was not designed for the reaction. This always requires a check of the existing frame.

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.

Skip it when: Snow load is heavy. Valleys drift, and they are the first place a wide roof gives you trouble.

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.

Skip it when: Interior walls, racking, or liner panel need a flat column face for their full height.

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.

Skip it when: Span is long and budget is tight. This is a usability premium, not an economy.

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