Frame types
Five configurations that decide where the columns stand and where the roof drains, and two column styles that decide whether the sidewall gives you a flat face to build against. The two choices are independent, so every building makes both.
The two things that actually eliminate options: how wide the building is, and whether anything can stand inside it. Read down the span column first — most configurations are ruled out by width before anyone gets to preference.
| Configuration | Span range | What it is | Skip it when |
|---|---|---|---|
| Clear Span | 20–300 ft | 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. | 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 | 60–480 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. | A column would land in a traffic aisle, a crane runway, or an arena floor. |
| Single Slope | 20–200 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. | Width is large. The high eave gets expensive fast because the whole frame grows with it. |
| Lean-To | 10–60 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. | The host building was not designed for the reaction. This always requires a check of the existing frame. |
| Multi-Gable | 80–600 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. | Snow load is heavy. Valleys drift, and they are the first place a wide roof gives you trouble. |
| Tapered Column | 40–300 ft | 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. | Interior walls, racking, or liner panel need a flat column face for their full height. |
| Straight Column | 20–150 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. | Span is long and budget is tight. This is a usability premium, not an economy. |
A photograph of a finished metal building shows the cladding, which is the one part of it this section is not about. These are sectional elevations on a common grid, so the differences you can see between them are the real differences between the frames.
A clear span frame is the default mental image of a metal building: two tapered columns, two rafters, one moment connection at each knee, and nothing at all standing between the walls. It is also the most expensive way to cover width, and the premium grows faster than the building does.
20–300 ft →A modular frame refuses to let any single member span the full width. One or more interior column lines split the building into modules, each rafter covers a fraction of the width, and the whole structure steps back down the curve that makes wide clear spans expensive.
60–480 ft →A single slope frame runs one continuous plane from a high eave to a low eave with no ridge at all. It is chosen for where the water goes, what the building looks like from the street, and what the zoning ordinance will allow — rarely for what the steel costs.
20–200 ft →A lean-to is a single-slope module framed off an existing sidewall. It has no ridge and no second column line of its own — the host building carries one side of it. That makes it the cheapest square footage available on any project, and the only frame type whose feasibility is decided by a building that already exists.
10–60 ft →A multi-gable frame is two or more gable modules side by side, sharing interior columns. It covers great width with short spans, which is the cheapest steel in the section — and it creates a valley, which is the most demanding roof detail in it.
80–600 ft →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.
40–300 ft →A straight column is a constant-depth member: heavier than the tapered equivalent carrying the same load, and worth it whenever something has to sit flat against it. This is a usability premium bought on purpose, not an economy.
20–150 ft →The list above mixes two independent choices, and it helps to separate them.
Clear span, modular and multi-gable are the same question asked three ways: how many column lines, and where. Below about 80 ft there is no question — a column saves nothing. Above it the answer is worth a growing share of the package, and past 300 ft there is no single-span option at all.
Single slope and lean-to are chosen for drainage, street presentation, height limits, and what is already on the site. They are rarely the cheapest steel and that is usually not why they are picked.
Tapered and straight columns are a separate axis entirely: any configuration above can have either. Tapered is lighter and cheaper and is the default over about 60 ft; straight buys you a flat, plumb face for racking, liner panel or wainscot, and you pay weight for it.
Application profiles from the frame selector: the typical width, the typical eave, and the configuration that usually falls out of them. A default, not a rule — the driver column is what actually decides it.
| Use | Typical width | Usual configuration | What sets the geometry |
|---|---|---|---|
| Aircraft Hangar | 100–300 ft | Clear Span | Door opening and tail height, not floor area. The clear span is set by the widest aircraft plus wingtip clearance. |
| Crane Bay / Manufacturing | 60–150 ft | Clear Span | Hook height drives the eave, and the crane runway loads the frame in a way roof snow never will. |
| Warehouse / Distribution | 100–400 ft | Modular | Rack grid and dock count. A column is free if it lands on a rack line, so modular almost always wins. |
| Riding Arena | 60–150 ft | Clear Span | A regulation arena floor cannot have columns in it. Width is set by the discipline, not the budget. |
| Self-Storage | 30–60 ft | Single Slope | Unit module and drive-aisle width. Single slope drains away from the doors. |
| Church / Worship | 60–120 ft | Clear Span | Unobstructed sightlines to the chancel. Clear span is the whole point of the building. |
| Agricultural | 40–100 ft | Clear Span | Equipment turning radius and the angle of repose of whatever is stored in bulk. |
| Retail / Office | 40–80 ft | Single Slope | Street presentation and parapet detailing. Frame cost is a minor line next to the facade. |
Pick one from your own numbers instead. The frame selector takes width, eave height, bay spacing, design loads, crane capacity and whether a column can stand inside, and returns a configuration with its reasoning and what the runner-up would have cost. If you already know the width, the span pages carry the same decision from the other direction.