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.
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.
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 of the battleground is corrosion. Rust. Steel cancer. Iron oxide. Fe2O3 (thanks John!).
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?
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 the 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 square 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 at 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.
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.
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.
- Galvanisers Association of Australia
- Austube Mills DuraGal Page
- Austube Mills DuraGal Plus Page
- Structural Pipe and Tube
- A House Raiser’s Guide to Steel Stumps
- Scott Metals Pricelist for Steel Stumps