Multi-Span Steel Buildings: Wide and Economical

A multi-span steel building uses rigid frames supported by one or more interior columns, dividing the width into two or more modules. The interior columns shorten the rafter spans, so frames and foundations become lighter, making very wide warehouses and factories more economical.

Key facts

Interior columns divide the width into modules, which reduces rafter bending.
Interior columns are often slender pipe, tube or built-up sections, pinned at the base.
Very wide buildings can be covered with one continuous roof.
Column positions should be agreed with the layout of racking, aisles or production lines.
A single gable roof over many modules avoids valley gutters.

How does a multi-span frame work?

The rafter runs continuously across the building and rests on interior columns as well as the sidewall columns. Each interior support reduces the span the rafter must bridge, which cuts bending and allows shallower, lighter sections.

Interior columns mainly carry vertical load, so they are often slender and pinned at the base. Lateral forces are still resisted by the frame action of the exterior columns and rafters, with the interior columns contributing according to the design.

Where are multi-span frames used?

Large warehouses, distribution centers, manufacturing plants, cold stores and agricultural buildings often use multi-span frames. In these buildings, fixed racking aisles or production lines can be arranged around a regular grid of interior columns.

The saving in steel and foundation size can be significant compared with a single clear span of the same width. The trade-off is reduced flexibility for future layout changes.

Planning interior column positions

Interior column spacing across the width is usually set to suit operations, for example racking bays, truck lanes or machine layouts. Module widths do not need to be equal, but a regular pattern simplifies design and fabrication.

Along the length, interior columns can sometimes be omitted at selected frames using jack beams to create larger open areas. This is useful near loading docks or production zones.

Roof shape and drainage

Most multi-span buildings use a single gable roof over all modules, which keeps drainage to the two sidewall gutters. Over very wide buildings, the ridge height and the roof run to the eaves increase, which affects gutter and downspout sizing.

An alternative is a multi-gable roof with valleys, which keeps the building height lower but adds interior gutters. The choice depends on rainfall, drainage routes and the height limits of the site.

Points to confirm with your engineer

Acceptable interior column positions and grid.
Clear heights at the lowest point of each module.
Rainfall intensity and gutter and downspout routes.
Areas where columns must be omitted using jack beams.
Protection of interior columns from vehicle impact.

Frequently Asked Questions

How many interior columns can a multi-span frame have?

There is no fixed number. Wide buildings may have several interior columns per frame; the number and spacing are set by layout needs and economy, confirmed by the project engineer.

Are interior columns protected from forklifts?

They should be where vehicles operate. Bollards, guards or concrete encasement at the base are common measures, specified by the owner or designer.

Can a multi-span building be extended sideways?

Yes, if planned. The sidewall can be designed for a future module, and the frame and drainage arranged so a new span can be added later.

Engineering content is general guidance. Every World Steel building is designed by qualified engineers to the code and loads of the project.