Tips & Tricks

Steel Posts – Duragal vs H.D. Galv

The Duragal steel post vs the Hot Dipped Galvanised steel post battle is a long-standing grudge match between two steely contenders.

Which steel post is better for your house project? Get the full blow-by-blow battle breakdown here.

The Battleground

Whether your project is a new house or an extension, if you are building a timber floor above ground, there’s a chance you’ll encounter the Duragal vs H.D. Galvanised steel stump battleground.

It’s not an easy battleground either. At stake are cost, longetivity, durability, corrosivity, availability and a whole host of other “itties” that cloud the decision process.

Steel columns under a house
Steel stumps under a house

Quite often steel stumps are open to the environment, easily seen but often ignored. The steel stump battleground is a forest of columns stretching from concrete footings to the underside of timber floor frames.

Steel column lengths can vary from less than 300mm to more than 5 metres. The columns support floors, walls, roofs, belongings and families. They are the critical support structure for our buildings. That’s why it is crucial you and your construction team make the right decision.

The Villain!

The villain of the battleground is corrosion. Rust. Steel cancer. Iron oxide. Fe2O3 (thanks John!).

Photos of a steel post that has corroded
Corrosion in a steel post

Steel’s affinity for water and oxygen is like red wine to a musketeer. Corrosion is the downfall of shiny steel stumps and the kryptonite of steel’s super strength. How can you protect yourself and your property?

The Hero!

Fortunately there is a hero: Standing between steel and evil corrosion is steel’s shiny coat of armour: Zinc.

When applied as a molten coating onto steel, zinc becomes the hero – bonding onto the steel surface and forming an impenetrable surface that staves off steel’s weakness to water and oxygen.

But steel has a choice that it must make before the battle: It must choose from a range of armours –  It must choose an armour that is light enough to be inexpensive yet strong enough to outlast the battle.

Behold the contenders!

Weighing in at 100g of zinc coating per square meter is DuraGal, marketed and sold by OneSteel. The lightest (and cheapest) of brand4the galvanised coatings, the zinc armour is only applied to the external surface of square (SHS), round (CHS) and rectangular (RHS) column sections.

The internal surface of DuraGal is a painted finish measuring only 35 micrometers (that’s 35 thousandths of a millimetre) thick.

Our next contender: Weighing in at 100g of zinc per sqimagesuare metre on inside and outside faces of box and round column sections is DuraGal Plus. It’s a better option than Duragal because the inside surface has a zinc coating too but it is slightly more expensive. If needed you can screw into DuragGal Plus or leave end caps off – but only in some environments. Check with your engineer.

Finally, our superhero: Hot Dip Galvanising. Weighing in Galvanisedat a hefty 500 grams of zinc per square metre inside and out, H.D. Galvanised steel has the heaviest, strongest coat but is also the most expensive. Steel has to be fabricated and then sent to the galvanisers to be dipped into a bath of molten zinc. It takes longer to arrive on site, makes on-site alterations harder but is super tough.

The Steel Stump Battle

It’s a fierce battle. What is the best thickness of galvanising for your project?

That’s a decision for you, your structural engineer and builder to make.

The Provisos

There’s a couple of issues you should be aware of:

It is well known in the construction industry that DuraGal steel and the chemicals in concrete react and fail the thin galvanised coating on DuraGal steel prematurely.

Corrode steel column
Duragal steel in contact with the ground will corrode

If you are casting DuraGal steel into a concrete footing, ask your structural engineer to document the precaution you need to take specific to your situation.

Yes, we’re talking about keeping your galvanised steel posts out of contact with the ground, uric acid and some other chemicals. Check with your structural engineer for your project.


We used the following websites to compile this article.

10 replies on “Steel Posts – Duragal vs H.D. Galv”

thanks Matthew

We have to replace our 30 year old wooden private power pole with a H.D. Galvanised 4.5mm thick steel pole due to site constraints.

I found your article as I was researching whether I could proactively increase its service life by applying a zinc coating before our electrician installs it.

From what I’ve read there would be no real advantage to doing this. Please correct me if I am wrong.

Also, is the use of quick setting concrete likely to exacerbate corrosion more so than standard concrete or using a tampered blue metal base?

Grateful for any advice

Everyone knows and agrees that DuraGal posts need additional protection if cast into concrete pads, if we want it to last many years , but what protection ? .. Everyone will tell you … “Ask your structural engineer … ” Shame that we do not have structural engineers in Australia , otherwise someone would “dare” to take a “risk” and recommend something. Are we all afraid to be sued if our opinion work out no to be the best possible ?


I fully agree with this document. Durgal in soil, is like having a Tissue Paper for a Rain Coat.

As a Forensic Structural Engineer, I have seen too many failures to allow Durgal to be in contact with soil. A SHS may last 5 years, and not 50 Years.

What would be the effect of including a simple layer of damp proof course stocking/sock…between the durogal post and it’s stump or other such support surface? whaddya mean they don’t make’em?

I had a Welding contractor weld 10mm Baseplates to my Steel House stumps and Verandah Posts.
The Duragal is 3.5mm thick and the stumps are around 1300mm long.
He sprayed cold Galv over the plates and the welding.

He assures me that this will be there for 70 years.

Does anyone have an opinion on this.?

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