Underpinning FAQ — Port Stephens

It varies with the scope. A single corner underpin (one section of footing) might be $3,000–$6,000. A full perimeter underpin of a typical house is usually $15,000–$40,000 depending on depth, soil conditions and access. Screw pile underpinning can sometimes be cheaper for sandy soils. You'll need a structural engineer's report first (around $500–$1,200), which specifies exactly what work is required — then contractors quote against that specification.

Yes — in almost every case, a structural engineer's report is required before underpinning work begins. The engineer inspects the building, assesses the soil conditions, identifies the cause of movement, and specifies the underpinning method, depth and extent needed. This report is also what council requires if you need a CDC (Complying Development Certificate) for the work, and it protects you by ensuring the contractor does what's actually needed — no more, no less.

A single section (one corner or one wall) is usually 3–5 days. A full house underpin can take 2–4 weeks depending on the method, soil conditions and access. Screw pile work is generally faster than traditional concrete underpinning. Weather delays can extend the timeline — you don't pour concrete in heavy rain. Your contractor will give you a realistic schedule with the quote.

Usually yes. Traditional concrete underpinning is done in sections — they excavate and pour one section at a time, so the building is always partially supported. Screw piling is less disruptive again. There'll be noise, vibration and excavation around the perimeter, and you may lose access to parts of the yard. Most families stay in the house and treat it like any other building work.

The main causes are reactive clay soils (they shrink when dry and swell when wet, moving the footing with them), trees drawing moisture from the soil near foundations, poor original design or construction, plumbing leaks saturating the ground under the slab, and fill that wasn't properly compacted. In coastal Port Stephens, sand wash-out from stormwater flow is another factor. A structural engineer can identify which cause applies to your property.

Underpinning stops further movement — which stops new cracks forming and existing ones getting worse. It doesn't cosmetically repair existing cracks. After underpinning, a builder or bricklayer can repair the cracks (repointing mortar, patching render, stitching masonry). Most underpinning contractors can recommend someone for the cosmetic repair work, or handle it themselves.