The difference between cold-formed vs hot-rolled steel is how the section is shaped. Hot-rolled sections are rolled while the steel is hot and are heavier. Cold-formed sections are bent from thin steel at room temperature and are lighter. In a steel building, each has a place: cold-formed for purlins and girts, hot-rolled or built-up for the main frame.
Cold-formed vs hot-rolled steel: how each is made
Hot-rolled steel is rolled at high temperature in a mill into shapes such as I-beams, H-beams, angles and channels. The result is a thick, sturdy section with consistent properties.
Cold-formed steel starts as a thin strip or sheet. Rollers or presses bend it at room temperature into shapes such as C, Z and hat sections. The forming process makes it light and allows long lengths with accurate profiles. The process is described in this overview of cold-formed steel.
Where each is used in a building
| Member | Usual section | Why | |—|—|—| | Main columns and rafters | Hot-rolled or built-up | Heavy loads, thick material, welded connections | | Roof purlins and wall girts | Cold-formed C and Z | Light, long, repeated across the building | | Mezzanine joists | Either | Depends on span and load | | Bracing | Hot-rolled angles or rods | Simple connections and tension capacity |
Many buildings use both. The frame is hot-rolled or fabricated from plate, and cold-formed members connect the frame to the cladding. Our guide to C purlin vs Z purlin shows how the cold-formed sections work on a roof.
Strengths and limits of each section
Neither section is better everywhere. The comparison below helps to decide which one suits a particular member, and it is a good starting point for a conversation with the engineer. Think about cold-formed vs hot-rolled steel as a choice for each member, not a choice for the whole building.
- Weight: Cold-formed sections use less steel for light loads, which saves transport and erection effort.
- Thickness: Thin material is more sensitive to local buckling and to corrosion, so coating matters.
- Connections: Cold-formed members are usually bolted, while heavy hot-rolled and built-up members are often welded.
- Size range: Hot-rolled sections are available in standard sizes, while built-up sections allow tailored depth, as explained in our note on built-up H-beams and hot-rolled beams.
Choosing for your project
- Match the member to its job: primary frame or secondary member.
- Check availability of the section and the lead time.
- Consider coating and the site environment.
- Ask the engineer to confirm the design checks for thin sections.
- Compare the total installed cost, not the price per ton.
A short note from the engineer on why each section was chosen also helps later, when the building is extended or modified and someone needs to know what the original design assumed.
When you compare steel building manufacturers, ask which sections they roll in-house and which they buy in. In-house production gives control over thickness and length. At Truong Thinh, C and Z purlins are hot-dip galvanized, and our steel purlin page lists what we supply. The wider process is in our guide to pre-engineered steel buildings versus conventional steel buildings.
If you are unsure which section suits your frame, contact the engineering team and describe the span, the loads and the building type.
Frequently Asked Questions
Is cold-formed steel weaker than hot-rolled steel?
Not in general. It is thinner, so it behaves differently and is checked for local buckling. It is designed and used for the right members.
Can cold-formed sections be used for columns?
In light structures, yes. For large industrial frames the main columns are usually hot-rolled or built-up.
Do both need coating?
Yes. The coating depends on the exposure, and thin cold-formed sections benefit from galvanizing.
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