Once you have decided to restump, the next question is what to put under the house. In practice, the choice is between reinforced concrete and galvanised steel. Timber is rarely used for new stumps in Melbourne now.

Reinforced concrete stumps

Concrete stumps are precast with steel reinforcing bar inside. They are made in standard lengths and stood in a hole on a concrete pad. The bearer above is tied down to the stump with a galvanised strap or bolt, and the final height is set with packers between the stump top and the bearer.

What they are good at:

Low and medium crawl spaces, where stumps are short and do not need much bracing.
Stable conditions once the footing has reached firm ground.
Set-and-forget installations where the owner does not want to think about adjustment later.

What to watch for:

Weight. Long concrete stumps are heavy and awkward to carry through tight side passages.
Fixed height. If the floor moves later, adjustment means changing packers.

Galvanised steel stumps

A steel stump is a length of galvanised hollow section on a flat foot. Adjustable versions carry a threaded rod at the top for raising or lowering by small amounts. The foot plate is fixed to a poured pad.

What they are good at:

Reactive clay, where the floor will probably shift again and quick tweaks save a re-pack.
Tall stumps on sloping blocks, where long concrete stumps would be heavy and need more bracing.
Tight access, because steel stumps are lighter to carry in.
Fine levelling during installation, since the adjustable top makes small height changes easy.

What to watch for:

Moisture. Steel needs a dry, well-ventilated subfloor and good detailing at the base so water does not sit against it.
Cost. Adjustable steel is generally more expensive per stump than concrete.

How the north shapes the choice

The basalt plains

Across Coburg, Pascoe Vale, Glenroy, Reservoir, Fawkner, Thomastown, Lalor, Broadmeadows and Craigieburn, the soil is highly reactive clay. Floors here tend to move, even on good stumps. Adjustable steel makes later fine-tuning simpler. Concrete is also widely used and performs well, with re-packing as the adjustment method.

Sloping blocks in Banyule

Around Ivanhoe, Heidelberg, Rosanna, Macleod, Watsonia and Greensborough, many houses have tall stumps on the low side. Steel is often the practical choice for tall runs because it is lighter and easier to brace. Concrete may still suit the shorter stumps on the high side.

Inner-north cottages

In Brunswick, Northcote and Thornbury, crawl spaces are often low and access is tight. Short concrete stumps suit low crawl spaces well, but carrying them through a narrow passage takes time. Steel can help where access is very tight.

Mixing stump types

There is nothing wrong with using both. A common approach is concrete under the main part of the house and adjustable steel under a tall section at the rear. What matters is that the stumps are correctly sized, braced and tied down, and that the floor is set level across the change.

What about footings?

The stump gets the attention, but the footing does most of the work. How big and how deep each footing goes is decided on the permit drawings, using the soil report and the loads involved. On the northern plains, that often means digging through clay and sometimes into basalt. The footing is inspected before concrete is poured.

Which one lasts longer?

Both are long-term materials when they are installed properly, and both are a big step up from timber. Concrete's weak points are poor reinforcing cover and cracking from impact during installation. Steel's weak point is corrosion, which comes down to galvanising quality, keeping soil and water off the base, and subfloor ventilation. In a well-drained, well-ventilated subfloor, either should serve the house for a very long time. In a damp, poorly ventilated one, fixing the moisture problem matters more than the choice of stump.

Questions to ask your restumper

Which stump type do you recommend for my house, and why?
Will any stumps need bracing?
How will the stumps be tied down to the bearers?
What footing depth is specified?
Can you price both concrete and steel?

Our view

There is no single right answer. We recommend based on crawl-space height, soil, slope, access and how you want to manage the house in future. If you want to compare, we will price both. Ask for a free inspection; the recommendation comes after we have crawled under your floor, not before.

Concrete or Steel Stumps for a Northern Suburbs Restump?