How Do You Know If Your House Needs Restumping or Underpinning?

Rao Hasnain • August 31, 2026

Wollongong Home Needs steel and concrete Restumping

If your home sits on timber stumps and you're seeing sloping floors, sticking doors, or visible gaps around skirting boards, that's usually a restumping issue. If your home is on a concrete slab and you're seeing cracked brickwork, stepped cracks in mortar lines, or cracks in the slab itself, that points toward underpinning. Some homes, particularly older properties that have been extended or partially rebuilt, show signs of both and need each area assessed separately.

Restumping vs Underpinning, What's the Difference?

These two terms get used interchangeably by homeowners, but they solve different structural problems.

Restumping replaces the timber, concrete, or steel stumps that support a raised timber floor. It applies to the classic Australian elevated home, common throughout older parts of Wollongong and the Illawarra, where the floor sits above the ground on a series of individual stumps rather than directly on a slab.

Underpinning strengthens the footings under a home, typically one built on a concrete slab or with shallow existing footings. Rather than replacing individual stumps, underpinning extends or widens the footing itself, usually by digging down to more stable ground, so the existing foundation gains additional support from below.

The confusion is understandable because both are triggered by the same underlying problem: the ground moving under your home. Which fix applies comes down to how your house is built, not how it's moving.

Signs Your House May Need Restumping

These signs are most relevant if your home has a raised timber floor on stumps, which describes a large share of older housing stock across the Illawarra.

Sloping, bouncy, or uneven floors, particularly noticeable when you roll something round across the room and it drifts toward one side
Doors or windows that stick, or no longer close flush against their frames
Visible gaps opening up between walls, floors, or skirting boards
A noticeable tilt when standing in one part of the house compared to another
Damp, musty smells from under the house, often a sign of moisture reaching the stumps
Visibly rotted, cracked, or termite-damaged stumps, if you can get under the house to check
A home that's never been restumped, especially one built before the 1970s on its original timber stumps

Restumping issues tend to be localised to one area first, near a leaking downpipe, a low corner of the block, or wherever drainage is worst, before spreading if left unaddressed.

Signs Your House May Need Underpinning

These signs are more relevant for homes on a concrete slab, or homes with shallow or ageing footings.

Cracks in external brickwork, especially diagonal, stepped cracks that follow the mortar lines
Cracks in the concrete slab itself, particularly if they're widening over time
Doors and windows misaligning in a home that sits on a slab rather than raised stumps
Gaps appearing between the slab and external walls or paving
Visible movement or cracking around window and door frames
A slab that feels uneven or sloped underfoot in different rooms

Underpinning signs tend to show up more gradually and are closely tied to soil movement, especially the reactive clay found across much of the Illawarra, which expands when wet and contracts when dry, placing ongoing stress on shallow footings.

Restumping vs Underpinning Signs at a Glance

Sign	More Likely Restumping	More Likely Underpinning
House type	Raised timber floor on stumps	Concrete slab or shallow footings
Floor movement	Sloping, bouncy floors	Slab feels uneven, but doesn't bounce
Wall cracking	Less common unless severe	Stepped, diagonal cracks common
Door and window issues	Sticking, misaligned frames	Misaligned frames, gaps at slab edge
Underlying cause	Rotted, termite-damaged, or ageing stumps	Reactive clay, shallow footings, moisture
Typical trigger point	Poor drainage, ageing timber, moisture under the house	Soil expansion and contraction, poor original footing depth

Can a House Need Both?

Yes, and it's more common than most homeowners expect, particularly on older Wollongong properties that have been extended over time. A house that started as a small raised timber cottage and later had a slab-on-ground extension added can genuinely need restumping under the original section and underpinning under the newer one. Reactive clay doesn't care where the boundary between the two sits, it puts pressure on whatever foundation type is above it.

This is exactly why a proper assessment looks at each part of the house separately rather than assuming one fix applies everywhere.

What Happens If You Ignore the Signs?

Foundation movement doesn't resolve itself, and in most cases it gets more expensive to fix the longer it's left.

Small, localised settlement can spread into wider structural movement
Hairline cracks can widen into major structural cracks in load-bearing walls
Sticking doors and windows are often an early warning, not the main event
Water ingress from cracks or gaps can accelerate soil movement and timber rot
What starts as a partial restump or minor underpinning job can become a full structural intervention if left for years

Catching movement early is almost always the difference between a contained, affordable repair and a much larger project.

What To Do If You're Seeing These Signs

A visual checklist is a useful starting point, but it isn't a diagnosis. The same symptom, a sloping floor or a cracked wall, can point to different causes depending on your soil, drainage, house age, and construction type. The only reliable way to know whether you need restumping, underpinning, or a combination of both is a proper on-site inspection, ideally one that includes a look at your subfloor or footings directly rather than a guess from the outside.

Frequently Askes Questions

Is restumping cheaper than underpinning?
Generally, yes, restumping tends to cost less than underpinning on a like-for-like basis, since it typically involves replacing existing stumps rather than extending footings into deeper ground. Exact costs depend heavily on the scope, access, and number of stumps or footings involved.
Can I restump part of my house and underpin another part?
Yes. This is common in homes that have been extended or partially rebuilt over time, where different sections of the house have different foundation types.
How urgent is it once I notice sticking doors or sloping floors?
It's worth booking an inspection as soon as you notice these signs rather than waiting. Early-stage movement is usually cheaper and less disruptive to fix than movement that's been left to progress for years.
Do reactive clay soils in the Illawarra make this worse?
Yes. Clay-heavy soils common across much of the Illawarra expand when wet and contract when dry, which places ongoing stress on both stumps and shallow footings, making early intervention particularly valuable in this region.
Will insurance cover restumping or underpinning?
This depends on your policy and the cause of the movement. Gradual wear and soil movement are often excluded, while sudden events may be covered differently. It's worth checking your specific policy or asking during your inspection.