The steel frame is where a prefab building earns its stability. Panels close the building, but the MS structure carries the main load path into the foundation. Choosing a box pipe by thumb rule can create problems later.
What does the MS structure do?
The MS structure carries building loads and transfers them to the foundation; panels primarily form the envelope and are not a substitute for structural design. A light prefab frame may use box sections, channels or other steel members for columns, beams, rafters, purlins and bracing.
Which pipe sizes are commonly used?
Common light-frame projects may use MS box sections such as 40×40, 50×50, 60×40, 75×40 or 80×40. These are examples of available sections—not universal design recommendations. Section thickness matters as much as outside dimensions.
For a 20 × 10 ft site office, footprint alone is not enough to choose steel. Roof load, wind, column spacing, opening positions and support conditions are all required.
How do you estimate steel structure weight?
A preliminary estimate starts with member length multiplied by published mass per metre, then adds plates, brackets, connections, bracing and secondary steel. Final steel tonnage should come from engineered fabrication drawings, not a quantity estimate alone.
Loads that must be checked
A structural frame should be checked for dead load, imposed or live load where applicable, wind and project-specific actions, with strength and serviceability checked under the applicable design standard. For Delhi NCR, wind can govern lightweight structures, especially exposed rooftops — see examples in our completed rooftop and site installations.
- Check roof loading and maintenance access where applicable.
- Check wind pressure, uplift and frame deflection.
- Check base plates, anchors and the foundation or rooftop interface.
- Do not treat panel weight as the only load.
Specify requirements before member sizes
State the building dimensions, clear height, roof type and slope, location, occupancy, equipment loads, openings and large door positions. Require structural drawings and connection details before fabrication, and specify steel grade, corrosion protection and fabrication quality. Our team can help translate these requirements into a fabrication-ready design — reach out to discuss your project.
Why trusses and purlins matter
Trusses or rafters create the roof load path while purlins support roof panels between primary members. Increasing purlin spacing without checking panel capacity can cause excessive deflection or damage. Coordinate panel allowable span with the structural calculation before finalising purlin spacing.
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