Concrete: the default
Reinforced concrete stumps are what most Australian houses get today. Immune to rot and termites, strong in compression, cheap to make and available everywhere. Their weaknesses are brittleness — a concrete stump can crack if ground movement loads it sideways — and, in older or cheaply made examples, "concrete cancer", where moisture reaches the internal steel and rusts it until the stump splits. Modern stumps with proper cover and galvanised tie wire largely avoid this. Expect them to be the baseline price in any quote.
Steel: the upgrade
Galvanised steel stumps cost roughly $50–$150 more per stump but bring two real advantages: they tolerate lateral movement without cracking (which is exactly what reactive clay dishes out), and many systems are adjustable — the house can be re-levelled later by turning a head assembly rather than jacking and packing. They're also lighter to handle in tight crawl spaces. The caveats: quality galvanising matters near the coast, and in aggressively saline or acidic soils steel needs the right coating spec. On heavily reactive clay blocks, steel is usually the smart money.
Timber: the heritage option
New hardwood stumps (typically treated or naturally durable species like red gum or ironbark) are still used — mostly for heritage accuracy, partial restumps matching existing stumps, or budget jobs. Modern treated timber outlasts the old untreated stumps it replaces, but it remains organic material in the ground: decades, not a century, and termite management stays on your calendar forever. Some councils and heritage overlays effectively require it; otherwise it's rarely the best value today.
Side by side
- Lifespan: concrete 50–80+ years; steel 50–100 years with correct galvanising; timber 20–50 years by species and site.
- Cost: timber cheapest, concrete the baseline, steel a modest premium per stump that mostly disappears in whole-job pricing.
- Reactive clay: steel best (flexes, adjustable), concrete adequate, timber worst.
- Termites/rot: concrete and steel immune; timber managed, never immune.
- Re-levelling later: adjustable steel wins outright; others need re-packing.
How to choose
Ask each quoting contractor two questions: what's the soil doing here (they'll know the street), and what would they put under their own house on this block. On stable soil, concrete is fine and the cheapest good answer. On known reactive clay — most of Melbourne's west and north, much of Adelaide — the steel premium is cheap insurance. Match-the-existing makes sense only in partial restumps. And whatever the material, insist the quote specifies stump size, footing depth and the levelling standard in writing — material choice can't rescue a shallow footing.
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Common questions
Can stumps be mixed — steel where it matters, concrete elsewhere?
Yes, and it's common sense on part-reactive blocks: adjustable steel under the wet or clay-affected side, concrete for the rest. Contractors do it routinely; just make sure the quote maps which goes where.
Are adjustable stumps worth it?
On reactive clay, strongly yes — a future re-level becomes a service call instead of a restump. On stable ground they're paying for flexibility you may never use.
My quote says 'concrete stumps' with no size or depth — is that normal?
It's common, and it's not good enough. Stump cross-section and founding depth drive performance; a professional quote states both, because the permit drawings will need them anyway.