Underpinning is taking an existing footing down to ground that will actually hold it. Either because the ground it is sitting on has moved, or because someone is about to dig next to it and it needs support before they do.
We do both. Houses that have started to crack and move, and commercial work where a footing has to be supported before a basement or a boundary excavation goes in next door.
Underpinning is engineered work. A structural engineer designs it, it is carried out in a sequence that keeps the building standing the whole time, and it is not something to buy on price alone. Done badly it makes the problem worse.
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Where we work
Sydney and greater NSW out of our Marrickville yard, Brisbane and South East Queensland out of Slacks Creek, and along the East Coast for the right job.
If you want the detail for your city, we have a page for each:
Underpinning in Sydney and greater NSW
Underpinning in Brisbane and South East Queensland
Why a footing ends up needing it
Reactive soil. Clay swells when it is wet and shrinks when it dries. Over a few seasons that movement cracks brickwork and racks door frames. It is the most common cause in both Sydney and Brisbane, and Brisbane has a lot of it.
Water. A leaking stormwater line, a broken sewer or a downpipe discharging beside a footing will soften the ground under it. Fix the water first or you will be underpinning the same house twice.
Trees. A large tree close to a building draws moisture out of clay and drops the ground under one corner. Removing the tree can make it worse before it makes it better.
Fill. Plenty of older residential sites are built on fill that was never compacted properly. It settles for decades.
Somebody digging next door. The one that is nobody's fault until it is. An excavation beside an existing footing removes the support beside it.
Mass concrete, piles or resin
Three broad methods. The right one depends on the soil, the load and the access.
Mass concrete. Excavate in short sections beneath the footing and fill with concrete, working down to competent ground. Traditional, well understood, and the one most residential jobs end up using.
Piled underpinning. Screw piles or bored piles taken down to load bearing strata, with needles or a beam transferring the footing onto them. Suits deep soft ground, high loads, and situations where you cannot excavate beside the building.
Resin injection. Expanding resin injected into the soil to lift and stabilise. Quick and clean, and genuinely useful in the right ground. It is not a substitute for a structural footing where the load is high, and anyone selling it as a cure for everything is selling you something.
We will tell you which one your job needs, and if it is the cheap one we will say so.
Supporting a footing before somebody excavates
If you are a builder about to dig a basement on a tight site, this is the part that holds up your programme if it is left late.
The neighbouring footing has to be supported before the excavation reaches it, not after. That usually means underpinning along the boundary, often combined with structural propping and sometimes with shoring. It needs a design, it needs notice to the adjoining owner, and it usually needs a dilapidation report.
We do the propping as well, so it is one contractor for the temporary works and the permanent support rather than two arguing about sequence.
The sequence is the whole job
You never excavate the whole length of a footing at once. The wall would have nothing under it.
Work goes in short alternating sections, each one excavated, poured and allowed to gain strength before the next one beside it is opened up. On a long wall that means a lot of small careful stages rather than one big dig, and it is why underpinning takes the time it takes.
Anyone quoting you a fast programme on an underpinning job has either not read the design or is not planning to follow it.
Frequently asked
Do I definitely need underpinning? Maybe not. Get the cracking assessed first. Some movement is seasonal and cosmetic, some is a drainage problem that costs a fraction to fix. We would rather tell you that than sell you a job you do not need.
Can we stay in the house? Usually yes. It is noisy and there will be excavation beside the building, but it is not normally a reason to move out.
How long does it take? Depends entirely on how many metres and how deep. The sequencing sets the programme, not the crew size.
Do you need an engineer? Yes, and if you do not have one we can bring one in. We install to a design, we do not improvise it on site.
Do you work outside Sydney and Brisbane? Yes, for jobs of the right size. Ask.
Tell us the address and what it is doing
Photos of the cracking, roughly when it started and whether it is getting worse will tell us a lot before anyone visits. If there is an engineer's report, send that too.
We will tell you straight whether it needs underpinning, whether it needs a plumber first, or whether it needs watching for another season.
Sydney 02 7908 4944. Brisbane and South East Queensland 07 2145 6581.
Perfect Stripout & Demolition acknowledges the Aboriginal and Torres Strait Islander people as Traditional Custodians of the country on which we live and work. We pay our respects to the Traditional Custodians and Elders past, present and future, and honour their connection to the land and ongoing contribution to society.