The good news is that underpinning is not always the only option. Some homes may need traditional underpinning, particularly where deeper structural support is required. Other homes may be suitable for house re-levelling, resin injection, ground improvement, void filling or slab lifting, depending on the cause and extent of the movement.

Mainmark has provided ground engineering and foundation repair solutions since 1989. Across Australia, Mainmark helps homeowners understand and address problems caused by foundation movement, house subsidence, weak or reactive soils, voids and foundation settlement.

The best first step is not to guess the repair method. It is to identify why the house is moving.

You may need underpinning if your home requires deeper structural support or if the existing footing system is no longer adequate. However, if the problem is caused by weak ground, voids, localised settlement or a sinking slab, your house may be suitable for an alternative re-levelling or ground improvement solution.

In simple terms:

• Underpinning adds or extends structural support beneath existing foundations.
• House re-levelling aims to lift and re-support areas that have dropped or moved.
• Ground improvement treats the support conditions beneath the structure.
• Resin injection can help fill voids, improve ground support and, where suitable, assist with re-levelling.

So, do you need underpinning? Maybe. But you may also have other options. The right solution depends on your soil conditions, foundation type, severity of movement, drainage, site access and whether the movement is still active.

Underpinning is a traditional foundation repair method that usually involves excavating beneath or around existing footings and installing new support, often using concrete.

It is designed to strengthen or deepen the foundation support where the existing footings are not performing as needed.

Underpinning may be recommended where:

• Foundations need to transfer loads to deeper ground
• Existing footings are inadequate or damaged
• Settlement is significant or widespread
• Structural engineering advice confirms underpinning is required
• The home cannot be effectively supported through ground improvement alone

Underpinning can be effective in the right situation. However, it may involve excavation, access challenges, concrete works, longer timeframes and disruption to landscaping, paving, driveways or surrounding areas.

Is underpinning always required for a sinking house?

No. A sinking house does not automatically need underpinning. Some homes may be re-levelled or supported using less invasive foundation repair methods, depending on what has caused the movement.

House re-levelling is the process of lifting and re-supporting areas of a home that have settled, dropped or moved out of level.

For Australian homeowners, this may be relevant if part of the home has sloping floors, uneven floors, cracks in walls, sticking doors or visible signs of foundation settlement.

Depending on the site, house re-levelling may involve resin injection, ground improvement, slab lifting, void filling or other structural support solutions.

The goal is not simply to hide the damage. The goal is to improve support where movement has occurred and help return affected areas closer to their intended level, where suitable and safe to do so.

Can a house be re-levelled without traditional underpinning?

In some cases, yes. If the movement is linked to weak ground, voids, sinking slabs or localised foundation settlement, non-invasive re-levelling options may be suitable. A site assessment is needed to confirm this.

Underpinning and house re-levelling can both be used in foundation repair Australia-wide, but they are not the same.

Underpinning supports the structure: Traditional underpinning generally focuses on adding new structural support beneath existing foundations. This may involve excavation and concrete to extend or strengthen the foundation system.

Re-levelling corrects movement where suitable: House re-levelling focuses on lifting and re-supporting parts of the home that have dropped or settled. It may be used where the structure has moved due to ground conditions beneath the slab or footings.

Ground improvement treats support conditions: Ground improvement focuses on improving the ground that supports the home. This may be important where weak soils, voids, erosion, poor compaction or moisture-related soil changes have contributed to movement.

Resin injection may offer a less invasive option: Resin injection foundation repair involves injecting an engineered expanding resin into targeted areas beneath the home. As the resin expands, it can help fill voids, improve ground support and, in some cases, assist with lifting and re-levelling affected areas.

Some homes do need traditional underpinning or another engineered structural solution.

Underpinning may be required when:

• The foundation requires deeper support
• The movement is severe, complex or widespread
• Existing footings are structurally inadequate
• The ground immediately beneath the footing cannot provide enough support
• Engineering advice recommends structural underpinning
• A non-invasive foundation repair method is not suitable for the site

In these cases, underpinning may be the most appropriate option. The important point is that this should be determined after proper investigation, not assumed from wall cracks or sloping floors alone.

Alternative re-levelling methods may be suitable when the problem relates to localised foundation settlement, weak ground, voids, poor compaction, erosion or slab sinking. Mainmark’s non-invasive resin injection and ground improvement solutions may be considered for homes affected by:

• Sinking slabs
• Uneven floors
• Sloping floors
• Localised foundation movement
• Foundation settlement
• House subsidence
• Voids beneath slabs or footings
• Loss of support beneath part of the home
• Wall cracks linked to movement
• Sticking doors caused by frame distortion

This can be especially relevant for slab-on-ground homes, brick veneer homes and double brick homes built on reactive clay soils or sites affected by changing moisture conditions.

Drought, heavy rain, poor drainage, leaking pipes and soil washout can all affect the ground around and beneath a home.

Is resin injection a true underpinning alternative?

It can be, in the right conditions. Resin injection may reduce the need for disruptive excavation or traditional underpinning when the issue can be addressed through targeted ground improvement, void filling, slab lifting or house re-levelling.

For suitable homes, non-invasive re-levelling options may offer several practical benefits.

• Reduced excavation: Resin injection and targeted ground improvement usually require far less excavation than traditional underpinning. This can help reduce disturbance to gardens, paths, driveways and finished areas around the home.
• Faster installation: Because resin injection is targeted, it can often be completed more quickly than excavation-heavy repairs, depending on the property and scope of work.
• Minimal disruption: For homeowners living in the property, reduced disruption matters. Non-invasive foundation repair may help avoid large open excavations, extended site works and significant disturbance to daily routines.
• Targeted ground improvement: Resin injection can be applied to specific areas where support has been lost. This makes it useful where the issue is localised rather than affecting the entire home.
• Potential slab lifting and house re-levelling: Where suitable, resin injection may assist with lifting and re-levelling areas affected by slab sinking or foundation settlement.

Not every crack or uneven floor means your house needs underpinning. However, several symptoms appearing together may indicate foundation movement or house subsidence.

Common warning signs include:

• Wall cracks in house interiors
• Cracks in brick walls
• Stair-step cracks in brickwork
• Uneven floors
• Sloping floors
• Sinking slabs around the home
• Sticking doors or windows
• Gaps around windows or doors
• Skirting boards separating from floors
• Cracks returning after patching
• Garage floors, patios or driveways dropping

Are sloping floors a sign I need underpinning? Sloping floors can be a sign of foundation movement, but they do not automatically mean underpinning is required. The cause of the movement needs to be assessed before choosing a repair method.

Choosing a repair method before understanding the cause can lead to the wrong outcome. A house may move because of:

• Reactive clay soils shrinking or swelling
• Poor drainage around the home
• Drought or changing moisture levels
• Heavy rain or stormwater problems
• Leaking pipes
• Voids beneath slabs
• Poorly compacted fill
• Erosion or soil washout
• Tree root activity
• Natural settlement

A professional site assessment helps determine whether the issue is cosmetic, seasonal, ongoing or related to foundation settlement. It also helps identify whether resin injection underpinning, resin injection, ground improvement, slab lifting, void filling or another structural support solution is the most suitable approach.

If you are worried your home needs underpinning, avoid rushing into cosmetic repairs before understanding the underlying issue. Try not to:

• Patch cracks without checking whether movement is continuing
• Trim sticking doors just so they close
• Replace flooring over a sinking slab
• Repaint walls before the cause of cracking is assessed
• Ignore poor drainage or leaking pipes
• Assume underpinning is the only option
• Assume resin injection is suitable for every home
• Delay assessment if symptoms are worsening

Cosmetic repairs can improve appearance, but they do not fix weak ground, voids, foundation settlement or house subsidence.

Mainmark can assess your property and help determine whether traditional underpinning, house re-levelling, resin injection, ground improvement, void filling, slab lifting or another structural support solution may be suitable.

If you have noticed wall cracks, brick cracks, sloping floors, uneven floors, sinking slabs or sticking doors, contact Mainmark to arrange a site assessment and understand your options before choosing a repair method.