120 ft clear span
At 120 ft the frame is still a catalog item, but what it does to the ground underneath it is not. A rigid frame pushes outward at the base, and at this width that horizontal thrust is large enough to change what the foundation has to be.
Priced as a 120 × 200 ft building at a 28 ft eave, 25 ft bays, 20 psf ground snow on the ASCE 7-16 basis, 115 mph wind, no crane — a case that matches what actually gets built at this width. Change any of it in the calculator.
Framing steel
6.41 – 8.92 lb/sf
Primary and secondary, 77 – 107 tons total
Building package
$19.43 – $24.82/sf
$466K – $596K over 24,000 sf
Installed
$30.11 – $47.16/sf
$723K – $1.13M, before interior buildout
Modular would save
9%
About $48K on the package
Outside the usual range. This width prices outside the $14–22/sf band commonly quoted for metal building packages. That band describes ordinary spans; a 120 ft clear span legitimately leaves it, and clamping the figure to look tidy would make it useless exactly where it is most needed. How these figures were derived.
At this span: Deep haunches and heavier anchor-bolt patterns. Foundation cost stops being a rounding error.
The short answer
Get the foundation priced with the building, not after it. At this width a thrust detail the steel quote never mentions can cost more than the gap between two frame quotes.
Planning-stage estimate calibrated to published industry ranges. Not a substitute for a stamped design by a licensed engineer.
Geometry that follows from the width alone, at this page's 28 ft eave. These are planning rules, stated so they can be argued with — the derivations are on the methodology page.
| Dimension | At 120 ft | Why it matters |
|---|---|---|
| Frame depth at the haunch | 58–72 in | Span/25 to span/20. The deepest point of the frame, at the knee, where the moment peaks. |
| Clear height at the sidewall | 22–23.2 ft | Eave height minus the haunch. The height you can actually use in the first bay in from the wall; clearance rises toward the ridge. |
| Rafter half length | 60 ft | Haunch to ridge. What has to get on a truck. |
| Shipping pieces per half | 2 | Past ordinary haul length, so the half arrives in bolted segments and each splice is a connection to make up in the field. |
| Deflection allowance, L/240 | 6 in | Allowable midspan movement with a non-plaster ceiling, per IBC Table 1604.3. The weight model behind this page checks none of it. |
| Engineering | Standard | Inside the 150 ft ceiling for a standard single-span rigid frame. Expect a quick, comparable quote from several bidders. |
A rigid frame is not a post holding up a beam. The knee joint transfers moment, which is what lets the building clear span, and the price of that is a horizontal reaction at each base trying to push the two columns apart. On a narrow building the footings absorb it without anyone thinking about it. At 120 ft they do not.
The usual answers are tie rods cast under the slab between opposing columns, hairpins developed into the slab reinforcement, a thickened grade beam, or larger footings relying on passive soil pressure. They cost different amounts, they constrain the slab pour and any under-floor trenching differently, and which one is right depends on soil the steel manufacturer has never seen.
This is the most common way a metal building comes in over budget at this width. The steel package is competitive and comparable between bidders; the foundation is neither, and it is often quoted by somebody else entirely. Anchor bolt patterns get heavier here too, which is a smaller cost but a real one.
Framing steel is about 6.41 – 8.92 lb/sf, and the haunch is 58–72 in deep — call it 22–23.2 ft of clear height at the sidewall under a 28 ft eave. Rafter halves are 60 ft, past ordinary haul length, so expect either permitted loads or a bolted splice in each half.
The modular saving is now around 9%. Clear span at 120 ft is a considered purchase, and the set of buildings that justify it is narrowing: hangars, crane bays, arenas, worship spaces, and distribution floors where a column would land in a dock apron.
Ask for the base reactions — vertical and horizontal, at each column, for the governing load combination. Every manufacturer produces them, they are the input the foundation engineer actually needs, and a bidder slow to hand them over is a bidder whose price is not yet real. Two frame quotes with different reactions are two different foundations, and the cheaper steel can easily be the more expensive building.
The uses whose typical width covers 120 ft, and what drives the geometry in each. A use that does not appear here is not impossible at this width — it is just not where it usually lands.
| Use | Typical width | Typical eave | What sets the geometry |
|---|---|---|---|
| Aircraft Hangar | 100–300 ft | 24–60 ft | Door opening and tail height, not floor area. The clear span is set by the widest aircraft plus wingtip clearance. Usually clear span. |
| Crane Bay / Manufacturing | 60–150 ft | 24–45 ft | Hook height drives the eave, and the crane runway loads the frame in a way roof snow never will. Usually clear span. |
| Warehouse / Distribution | 100–400 ft | 28–40 ft | Rack grid and dock count. A column is free if it lands on a rack line, so modular almost always wins. Usually modular. |
| Riding Arena | 60–150 ft | 14–20 ft | A regulation arena floor cannot have columns in it. Width is set by the discipline, not the budget. Usually clear span. |
| Church / Worship | 60–120 ft | 16–28 ft | Unobstructed sightlines to the chancel. Clear span is the whole point of the building. Usually clear span. |
A modular frame at this width comes in around 9% lower on the building package — roughly $48K on the 24,000 sf building priced above. That is real money rather than noise, so clear span at this width should be a decision rather than a default.
The frame selector's own recommendation for this case, with interior columns permitted, is a Modular frame with tapered columns. Web-tapered members follow the moment diagram and are the lightest way to carry this span.
Next step
A dealer quoting 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.