Specification guide · Goulburn Valley reactive clay

Concrete or galvanised steel stumps: which one actually suits Shepparton clay?

For the average Shepparton weatherboard, 100mm by 100mm precast concrete stumps on an engineered pad footing are the right call: $60 to $110 per stump supplied and installed, and 60 to 100 years in this soil. Galvanised steel adjustable stumps run $90 to $160 per stump and earn the premium only where you expect to re-level again: Class H clay, a big gum close to the house, or a home you intend to keep for decades. Timber is a mistake here at any price. The rest of this page is how to tell which one you are.

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The short version

Same strength, different future.

Concrete and galvanised steel stumps are both engineered to the same Australian Standard, AS 2870, for residential slabs and footings on reactive soils. Properly designed and founded at the depth the engineer specifies, either one will hold your floor. Anyone who tells you one is structurally superior to the other for a domestic restump is selling, not advising.

The real difference is what happens in year eight. Greater Shepparton sits on cracking clay laid down by the Goulburn and Broken rivers, classified Class M through to Class H under AS 2870. That ground swells through a wet winter and shrinks back through a dry summer. A correctly founded stump rides out most of that, but a house near a mature gum, on the deeper clay out toward the flats, or with a leaking stormwater line will still shift a few millimetres a season. With concrete stumps, correcting that means jacking the floor and repacking. With adjustable steel, it means a spanner and half a day.

So the honest question is not which material is better. It is: how likely is this house to need touching up, and is the extra $30 to $50 a stump cheap insurance against that? For most homes in Mooroopna, Kialla and central Shepparton, the answer is concrete throughout with steel on the rows most likely to move. Our stump replacement page covers how we mix the two on one job.

Sticky bit: the spec table

Stump options compared for Goulburn Valley conditions.

2026 rates, supplied and installed on an engineered pad footing, excluding permit, engineering and re-levelling. Life expectancy assumes correct founding depth and a subfloor that is not sitting wet all winter.

Option	Typical 2026 cost	Expected life here	Maintenance load	Warranty to expect	Who it suits
Precast concrete, 100mm by 100mm	$60 - $110 each	60 to 100 years	None. Cannot be adjusted without jacking.	Product warranty from the maker plus a written workmanship warranty, commonly 5 to 10 years	The default for almost every Shepparton weatherboard. Best value per year of service.
Precast concrete, 75mm by 75mm	$52 - $95 each	40 to 70 years	None, but less cover over the reinforcement	Same, but check the maker rates it for your load and height	Short stumps, light verandah and porch loads. Rarely worth the saving under a whole house.
Hot dip galvanised adjustable steel	$90 - $160 each	50 to 80 years	Low. Head can be wound to re-level, thread should be checked at any future service.	Coating certified to AS/NZS 4680 plus the installer’s workmanship warranty	Class H sites, houses near mature gums, wet-area rows, and owners who plan to stay.
Painted or pre-galvanised steel	$70 - $120 each	15 to 30 years at the ground line	High. Rust starts where the tube was cut or welded after coating.	Usually excludes corrosion. Read the exclusion before you accept it.	Nobody, under a house, in this soil. Avoid.
H5 treated pine	$45 - $85 each	25 to 40 years	Moderate. Splits and shrinks. Cut ends need re-treating on site.	Treatment warranty only, and it is void if a cut end goes in untreated	Sheds, decks and outbuildings. Not a house you want to restump once.
Recycled hardwood or red gum	$40 - $90 each	20 to 45 years, wildly variable	High. The exact failure you are paying to fix.	None worth the paper	Nothing structural. We do not install it.

Indicative Shepparton and Goulburn Valley rates for 2026. Your fixed quote follows a free subfloor inspection and the engineer’s footing design.

What the numbers mean

Reading a stump specification properly.

Concrete: section, grade and cover.

A precast concrete stump is described by three things. The section, usually 100mm by 100mm for a house or 75mm by 75mm for lighter loads. The concrete strength grade, quoted in megapascals, with domestic stumps generally made in the 25 to 40 MPa range. And the cover, which is how much concrete sits between the reinforcing bars and the outside face. Cover is the one nobody mentions and the one that decides whether the stump is still sound in 2090, because in wet Goulburn Valley clay it is the moisture reaching the steel that eventually splits a concrete stump, not the load.

What matters just as much is what the stump sits on. A stump is only as good as the pad footing under it, and on Class M to Class H clay the engineer sizes that pad and sets the founding depth so the base is below the zone where the soil moves with the seasons. A 100mm stump on a shallow pad in the active zone is a worse outcome than a 75mm stump founded properly. When you compare quotes, compare the footing note, not just the stump.

Steel: section thickness, the coating, and the thread.

An adjustable steel stump is a square hollow section with a base plate cast into or bolted onto the pad, and a threaded head that carries the bearer. Ask for three numbers: the section size, the wall thickness of the tube, and the zinc coating in microns. Hot dip galvanising to AS/NZS 4680 is applied after the stump is welded and drilled, so the zinc covers the welds, the drilled holes and the cut ends. Pre-galvanised tube that is cut and welded afterwards has bare steel at precisely the point that will sit at the ground line.

The thread is the other detail worth a question. A coarse thread with a large bearing plate is easy to wind under load years later. A fine thread packed with clay and never greased is not. Ask whether the adjuster is accessible from the crawl space once the floor is back down, because an adjustable stump you cannot reach is just an expensive fixed stump.

Timber: durability class and treatment.

If anyone proposes timber, the only legitimate specification is in-ground rated material: H5 treated softwood or a naturally durable Class 1 hardwood. Anything less is not rated for soil contact. Even correctly rated timber is a 25 to 45 year material in this district, and the original stumps you are replacing were hardwood that managed 40 to 70 years. We do not install timber stumps under houses, and we would tell you the same if you asked us to.

Local conditions

What Shepparton ground does to a stump.

Shepparton receives under 500mm of rain in an average year, most of it through winter and spring, and then bakes through a summer that regularly pushes past 40°C. That is the worst possible cycle for reactive clay: it takes up water, expands, then dries out and shrinks away. The soil classification under AS 2870 for much of Greater Shepparton is Class M to Class H, meaning moderately to highly reactive, and the difference between those two classes changes both the founding depth and the pad size in the engineer’s design.

Three local factors push a site toward the deeper, more conservative end of the design. Mature eucalypts and large deciduous street trees within roughly 10 metres of the house pull enormous volumes of moisture out of the clay through summer, which is why one corner of a house often drops and the rest does not. Old irrigation infrastructure and high seasonal water tables through parts of Mooroopna and the river flats keep the subfloor damp for months. And the October 2022 flood left plenty of homes across Shepparton and Mooroopna with saturated subfloors that never fully dried, which accelerated rot in stumps that had years left in them.

None of this changes the material choice on its own. What it changes is the founding depth, the pad size and how much attention the subfloor drainage deserves while the floor is up. Fixing blocked vents and a leaking downpipe while we are under there costs a few hundred dollars. Not fixing them is why the last set of stumps failed. Our subfloor repairs page covers what we look for, and the warning signs page covers what you can check yourself from inside the house.

Not sure which spec your house needs?

We crawl the subfloor, read the floor levels with a laser, and put the material recommendation in writing with the reason. Free, no obligation.

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The cheap spec

Five specifications that fail early in this soil.

A shallow pad footing. The single most common way to shave $1,500 off a quote is to dig the holes less deep. It is invisible once backfilled, it passes a casual look, and it puts the base of every stump inside the zone that swells and shrinks each season. Your floor will move again within three summers and you will pay for the job twice. The building surveyor’s footing inspection, with the holes still open, exists precisely to catch this, which is one more reason not to skip the permit.
Reusing the old holes. Dropping a new stump into the cavity left by the old one saves labour and gives you a stump sitting on disturbed, uncompacted fill. It needs a fresh excavation to undisturbed ground and a poured pad.
Packers instead of correct stump height. A stack of timber packers between the stump top and the bearer is a shortcut for a stump cut to the wrong length. Packers compress, rot and work loose. A small hardwood shim fixed in place is acceptable practice; a tower of them is not.
Steel that was galvanised before fabrication. Cheaper by roughly $15 a stump, and the bare cut ends and weld zones start rusting at the ground line where you cannot see them. Specify hot dip galvanising after fabrication.
New stumps, same wet subfloor. Replacing every stump while leaving the paved-over wall vents, the downpipe discharging beside the footing and the plastic sheeting that traps moisture is the most expensive false economy of the lot. It is a few hundred dollars of work that protects a five figure investment.

Sales language

What “commercial grade” is worth.

Nothing. Commercial grade, heavy duty, premium, industrial strength and builder’s grade have no definition in AS 2870, in the Building Regulations, or in any product standard that applies to a house stump. They are adjectives. A quote that leans on them and does not carry numbers is a quote you cannot compare with any other quote, which is usually the point.

A specification you can actually check reads like this: precast reinforced concrete stumps, 100mm by 100mm, on poured pad footings sized and founded per the engineer’s computations for the site classification, or hot dip galvanised adjustable steel stumps to AS/NZS 4680 with the coating thickness stated. Then a stump count, the re-level scope, the permit and the engineering as separate line items. If you have two quotes and only one reads like that, you already know which contractor has thought about your house. There is more on reading a quote line by line in how to choose a restumper.

Our recommendation

What we would put under a typical Shepparton house.

A three bedroom weatherboard of 40 to 70 stumps, on Class M clay, no large trees within 10 metres, dry subfloor: 100mm by 100mm precast concrete throughout, on engineered pads, with the wet-area rows under the bathroom and laundry done in galvanised adjustable steel. That mix adds roughly $400 to $900 to the job over all-concrete and buys you an easy correction in the one part of the house most likely to need it.

The same house on Class H clay, or with a mature gum close to a corner, or out on the flats where the water table sits high through winter: galvanised adjustable steel throughout. On 56 stumps that is roughly $1,700 to $2,800 more than concrete, and the first re-level it saves you pays most of it back, because winding adjustable heads is an $800 to $2,500 job against $3,500 to $8,000 to jack and repack a concrete stumped floor.

When you should not do any of this. If your subfloor inspection finds three or four perished stumps in one row and the rest are sound, dry hardwood with plenty of life, the right answer is to replace those stumps and fix the drainage, not to spec the whole house in steel because it sounds thorough. That is a $4,500 to $9,000 job, not a $20,000 one, and we will tell you so on the day. We also do not install timber stumps, we do not quote work without a building permit, and if what your house actually needs is underpinning rather than restumping, we will say that too, even though it is a different and usually dearer conversation.

Questions homeowners ask about stump material

Are concrete or steel stumps better for Shepparton soil?

For most Shepparton weatherboards, 100mm by 100mm precast concrete stumps on an engineered pad footing are the better value: about 60 to 110 dollars per stump supplied and installed, and 60 to 100 years of service life in Goulburn Valley clay. Galvanised steel adjustable stumps cost about 90 to 160 dollars per stump and earn that premium only where you expect to re-level again, which usually means a Class H reactive site, a large gum within about 10 metres, or a house you plan to hold for decades. Both are engineered to AS 2870 for the same soil class, so the choice is about future adjustability, not strength.

What size concrete stump should a Shepparton house have?

The Goulburn Valley default for a domestic restump is a 100mm by 100mm precast reinforced concrete stump, set on a poured pad footing that the engineer sizes for your soil class. Smaller 75mm by 75mm stumps exist and are cheaper by roughly 8 to 15 dollars each, but they carry less reinforcement and less cover over the steel, which matters in wet clay. On a 56 stump house the whole saving is only around 500 to 800 dollars, so it is rarely worth specifying down.

Can I use treated pine or hardwood stumps instead?

You can legally use timber if it is rated for in-ground use, which in practice means H5 treatment or a naturally durable Class 1 hardwood, but we do not install timber stumps in this district and we would advise against it. The original red gum and hardwood stumps under most pre-1980 Shepparton homes lasted 40 to 70 years in the same soil, and modern replacements sit in the same wet clay with the same subfloor damp. Spending 12,000 to 22,000 dollars on a full restump and then putting a 40 year material back under the house makes no sense when concrete costs about the same to install.

What does hot dip galvanised actually mean on a steel stump?

Hot dip galvanising to AS or NZS 4680 means the fabricated stump was dipped in molten zinc after it was welded and drilled, so the coating covers the cut ends, the welds and the inside of the section. The standard sets a minimum average coating by the thickness of the steel, and a heavier section carries a heavier coating. Ask for the coating figure in microns on the quote rather than accepting the word galvanised, because a painted or pre galvanised tube that was cut and welded afterwards has bare steel exactly where the ground line will sit.

Is commercial grade a real specification for stumps?

No. Commercial grade, heavy duty and premium are sales words with no definition in AS 2870 or in any product standard. The specification that actually matters is written as numbers: the stump section in millimetres, the concrete strength grade, the pad footing size and depth, the steel section thickness and the zinc coating in microns. If a quote uses the adjectives and not the numbers, ask for the numbers in writing before you sign anything.

Do galvanised steel stumps let you re-level the house later?

Yes, that is their real advantage. An adjustable steel stump has a threaded head that a tradesperson can wind up or down under load, so a later re-level is a half day job on the affected rows rather than opening the ground again. A re-level on adjustable stumps typically costs 800 to 2,500 dollars, against 3,500 to 8,000 dollars for jacking and repacking a concrete stumped floor. On a Class H clay site near the Goulburn floodplain that difference can pay for the steel premium the first time you use it.

Get a price

Get the stump specification for your house in writing

Send the form and we will book a free subfloor inspection, then quote the material, the stump count and the footing design as separate line items, usually within a few days.

One inspection answers it properly.

Concrete, steel or a mix of both depends on your soil class, your trees and how long you are staying. We read all three on site and put the answer in writing.

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