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Galvanised Steel Beams

Hot-dip galvanising for steel that is going outside, staying exposed, or living somewhere damp — arranged with the beam and delivered ready to install.

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Send us your engineer’s drawings and we’ll price the steel and the processing together — one order, one delivery, one point of contact.

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When galvanising is the right answer

Galvanising is for steel that paint will not protect for long enough. External canopies and porches, balcony and terrace framing, exposed frames on garden rooms, steelwork in a plant room or a swimming pool building, anything in a cellar or crawl space that is not reliably dry — these are the jobs where a painted beam becomes a maintenance problem and a galvanised one does not.

For a beam that is going to be plastered into a dry interior, galvanising is money spent on a problem that does not exist. Primer is enough.

How it differs from painting

Hot-dip galvanising is not a coating applied to the surface in the way paint is. The steel is cleaned and dipped in molten zinc, and the zinc forms a metallurgical bond with the steel. That bond is why it lasts: a galvanised finish is measured in decades in most environments, where a paint system needs maintaining and eventually redoing.

It also protects sacrificially. If the surface is scratched down to bare steel, the surrounding zinc corrodes in preference to the steel underneath, so a small area of damage does not become a rust spot that spreads. Paint does the opposite — damage lets moisture under the film.

Things to plan for

Galvanising happens by immersion, so the size of section that can be processed is limited by the physical size of the bath. Long members can sometimes be double-dipped, but it is a constraint to raise at quote stage rather than discover later.

Hollow sections need vent and drainage holes so that molten zinc can flow and air can escape. These have to be positioned as part of the fabrication and agreed with your engineer, not drilled as an afterthought.

The process involves heat, and long slender members can distort. If dimensional accuracy is critical, say so when you enquire. Any welding must also be completed before galvanising — welding a galvanised member afterwards destroys the coating locally and produces fumes that need managing.

Galvanised steel can be painted, but it needs the right preparation and primer. If a colour finish over galvanising is the intention, tell us so the system is specified as a whole.

What we need from you

The sizes and lengths, any fabrication that has to be done first, and where the steel is going — the environment drives the specification. Send the engineer’s drawings and we will quote the fabrication and the galvanising together with the steel.

Fabricate first, galvanise second. All cutting, drilling and welding must be finished before the steel is dipped. Working on a galvanised member afterwards destroys the coating at exactly the points that matter, and welding galvanised steel needs proper fume control.

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Common questions

Do I need galvanised steel for an internal beam?

Usually not. A beam that will be encased in a dry, heated interior is normally fine in primer. Galvanising is for external, exposed or damp conditions.

How long does galvanising last?

In most environments a hot-dip galvanised finish is measured in decades rather than years, and it protects sacrificially where the surface is damaged. The exact life depends on the environment and the coating thickness.

Can galvanised steel be painted?

Yes, with the correct preparation and primer for galvanised surfaces. Tell us at quote stage if a colour finish is wanted so the whole system is specified together.

Is there a size limit?

Galvanising is done by immersion, so section size is limited by the bath. It is worth raising the sizes and lengths involved when you enquire so this is settled before anything is ordered.

Ready for a price?

Send your drawings or a cutting list and we’ll come back with quantities and a price, steel and processing together. Large and small orders both welcome.

Get a free quote

We supply structural steel across London, the South and the Midlands, delivered direct to site. Information on this page is general guidance; specifications for your project must come from your structural engineer.