Underpinning in Sydney: where to start
Underpinning in Sydney is usually needed when a building's footings have moved. Common causes include reactive clay soils, poor drainage, leaking pipes or tree roots. Underpinning strengthens or deepens the foundations, but it should always follow an engineer's diagnosis, not a sales pitch for one repair method.
Cracks, sticking doors or uneven floors are observations, not a diagnosis. Soil conditions, drainage, construction and movement history can affect the investigation. Underpinning is one possible intervention; the appropriate response depends on the cause and the structure.
Signs it’s time to call a pro
- Diagonal cracks spreading from the corners of doors or windows
- Doors and windows that start to stick or won't close properly
- Floors that slope or feel uneven underfoot
- Gaps opening between walls, ceilings or skirting boards
- Cracks that get wider over the months
What’s usually included
Every property is different, but a good quote for underpinning should spell out items like these.
- Qualified structural assessment
- Relevant ground or drainage investigation
- Designed repair method and approvals
- Access, excavation and sequencing plan
- Monitoring and completion documentation
How much does it cost?
Reliable pricing depends on the investigation and the designed repair extent. Ask which professional reports are required, what is excluded and how discoveries during excavation will be managed. Avoid selecting a method solely because it has an attractive headline price.
How long it takes: Resin injection on a house can take as little as a day or two, while traditional concrete underpinning often takes several weeks, depending on the extent and access.
Licences, insurance and approvals
In NSW, underpinning and piering is its own licence class, so work over $5,000 (incl. GST) usually needs a contractor licensed for that class. The repair should be designed by a structural or geotechnical engineer, and some jobs also need council or certifier approval.
Every member of our crew has their NSW licence verified and insurance sighted before joining, and agrees to quote in writing with their licence number shown. Before you sign, confirm the licence number on the quote using the NSW Government licence check, and make sure residential work over $5,000 (including GST) has a written contract.
Have these details ready
A clear brief gets you faster, more accurate quotes.
- Age and type of building
- Where movement has been observed
- Any engineering reports already available
- Drainage changes and repair history
Underpinning: common questions
Do cracks mean underpinning is needed?
Cracks alone do not establish the cause or the repair method. A qualified assessment is needed before specifying underpinning.
Can I submit a report with my enquiry?
This preview does not accept file uploads. Describe the report in your brief; a secure document transfer process can be arranged only after a provider and destination are confirmed.
What causes foundation movement in Sydney homes?
Many Sydney suburbs sit on reactive clay that swells when wet and shrinks when dry, so long dry spells followed by heavy rain can move footings. Leaking pipes, blocked stormwater, poor site drainage and large trees close to the house can make it worse. An engineer looks at the soil, drainage and building to find the real cause.
What are the main types of underpinning?
Traditional underpinning digs under the footing and pours new concrete down to firmer ground. Screw piles and other piers carry the load deeper. Resin injection pumps an expanding resin into the soil to fill gaps and lift the slab. Each suits different soils and buildings, so the engineer's report should say which method fits and why.
Will home insurance pay for underpinning?
Many home policies exclude damage caused by gradual ground movement, settling or poor drainage. Some cover movement caused by a sudden insured event, such as a burst pipe. Read your product disclosure statement and talk to your insurer before work starts. An engineer's report on the cause will help with any claim.
Should I fix drainage before underpinning?
Usually, yes. If water keeps soaking the soil near the footings, new piers may not stop the movement. Engineers often recommend fixing leaking pipes, stormwater and site drainage first, then monitoring the cracks for a while. Sometimes that reduces the extent of underpinning needed, or avoids it altogether.