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Teretek® Resin Injection Underpinning Solution

Discover the modern alternative to traditional underpinning with Teretek® Resin Injection. This innovative solution offers a fast, clean, and cost-effective method for strengthening weak ground beneath subsided foundations.


Unlike traditional underpinning, which involves extensive digging and disruption , Teretek® requires no excavation and most projects are completed in just one day.


Choose Teretek® Resin Injection for a seamless and efficient way to raise, rel-level and re-support your property without the hassle and expense of traditional methods.

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Causes of a shifting house foundation in Sydney

Homes in many parts of Sydney may experience ground subsidence that leads to sunken building foundations.

Sinking floors, a visibly widening crack in the wall, an uneven concrete driveway, and doors and windows that won’t close properly can all be warning signs of ground weakness under a structure. If a building becomes un-level due to subsidence, the effects are not just cosmetic.

If left unaddressed, these symptoms can result in significant and expensive damage to the home and may also lead to safety issues for the occupants.

When cracks and other structural changes present themselves, homeowners may look for solutions, including underpinning services and contractors, to effectively ‘underpin’ their home.

Sydney is a unique region of Australia with challenging weather conditions, a variety of soil types and other factors that impact coastal and inland ground conditions.

In addition to extreme weather events, particularly torrential rain and storm activity, and extended periods of drought, Sydney homes may be affected by the following causes of foundation problems:

Leaking pipes

Over time, pipes under a property may deteriorate, become damaged or blocked, causing cracks which allow water to seep into the ground, both around and directly underneath the property. This is very common with clay pipes found in homes older than 20 years.  Leaky gutters and downpipes or dripping outdoor taps are also frequently identified as the source of water collecting near house foundations.

Inadequate drainage

Moisture management is key for good foundation and footing maintenance. If the soil does not have adequate drainage, water will collect causing the ground to weaken and potentially cause the home to subside or ‘sink’.

Poor building work

If there is insufficient ground preparation, including poorly compacted soil, before a house slab is laid, the ground may not be strong enough to support the load above. This is usually when house underpinning is considered, as well as other costly remediation works for fixing cracks in concrete surfaces, such as driveways.

Adjacent development

When building or renovation works take place at a neighbouring property, earthmoving and excavation can impact the stability of the soil on your side of the fence. This is even more problematic when coinciding with periods of heavy rain which soften the ground and may lead to soil erosion and voids.  Equally, the clearing of trees associated with development can affect the water table as moisture is no longer drawn out of the soil by the tree’s roots.

Tree roots

If pipes start to develop cracks and or have loose joints, tree roots will naturally grow towards these areas in search for water. Eventually, aggressive root systems will infiltrate pipes causing blockages that cause water to spill into the ground, impacting the stability of house foundations.

The Mainmark solution

Since 1989 Mainmark has successfully raised and re-levelled thousands of homes and driveways throughout New South Wales.

Mainmark offers some of the most advanced non-invasive resin injection technologies to quickly correct foundation ground issues with minimal mess or disruption.

With a sound knowledge of Sydney’s unique local conditions, Mainmark utilises its Teretek® engineered resin injection solution to effectively raise, re-level, and re-support footings under a home. Teretek® is a unique two-in-one solution that provides both ground improvement and re-levels homes, backed by a 50-year product warranty. It increases ground bearing capacity, fills voids, rehabilitates foundation ground which helps raise sinking floors and reduces wall cracking, all at a fraction of the cost of traditional underpinning, and with no detrimental effects on the environment.

A cost-effective alternative

Underpinning homes is generally a costly exercise using traditional methods due to the invasive nature of concrete underpinning, which is generally a lengthy and messy process. Teretek® is the modern way to raise, re-level and re-support your home by providing a unique two-in-one solution delivering both ground improvement and re-levelling.

Our ground improvement and level correction methods can address foundation subsidence and are effective for helping to fix cracks in walls or re-level sunken floors in homes of any size. Our solutions are also used for slab lifting foundation slabs and large driveways.

✓ Your location

✓ The actual cause of the problem – what other things need to be resolved as part of the works eg. drainage

✓ The nature and condition of the foundation soil – including an assessment of the soil type

✓ The type and profile of the building footings – are the existing footings damaged or in need of replacement?

✓ The surroundings e.g. access to the site, adjacent buildings or retaining walls

✓ Unknown or unforeseeable underground conditions – problem solving on site

✓ The volume of material that will be required – an estimate will be provided but may need to be re-assessed following more detailed ground investigation

✓ The time that the work will take – based on Mainmark’s extensive experience.



Why choose Mainmark?

New South Wale’s trusted re-levelling, ground improvement and void filling specialist since 1989.

Calling in experienced ground engineering consultants for an appraisal can help to quickly diagnose the issue and find a solution tailored to your home. Mainmark has raised, re-levelled and re-supported homes and buildings for over 30 years, delivering successful solutions to thousands of homes in Sydney from coastal to inland areas.

Our solutions are cutting edge and the modern answer to the traditional way to underpin. We can underpin, raise and re-level strip footings and raft slabs, plus we can infill slabs and driveways. Mainmark’s proprietary product Teretek® addresses building foundation problems, with minimal intrusion into the property and minimal interruption to the occupants, effectively underpinning by non-invasive expanding resin injection. In most cases, residents are not required to move out or move any furniture during the ‘home lift’ process.

In contrast, traditional concrete can be a slow process; involve excavation which causes mess; can reduce bearing capacity; cause differential movement between the underpinned sections of the structure and the rest of the structure; and be labour intensive.

Benefits & Features

Mainmark’s Solutions & Technologies


Our technologies have fast curing times and treated areas can be used immediately or without the delays compared to traditional repair methods.

Environmentally Inert

Our technologies use an inert material that is non-toxic and does not leach into the environment or affect the treated area.


Our solutions are of surgical nature compared to traditional methods.


Compared to traditional methods, our solutions are more cost-effective, with minimal disruption to the area.

How much does underpinning cost?

Arrange a site assessment in 3 simple steps:

Step 1

Submit your enquiry using our online form. Include a brief message about the type of foundation issues you are experiencing.

Step 2

Our friendly customer service team will be in touch to schedule a site assessment that suits you.

Step 3

One of the Mainmark experts will visit your commercial property, assess the damage, and ascertain the likely cause. They will establish the approach needed, creating a plan specific to the needs of your building and provide you with a detailed quote.

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Sydney by location

Helping to protect your biggest asset.

Sydney has a variety of soil types, including sand and very reactive clay soils, which shrink and swell according to moisture levels. While seasonal changes occur, a mixture of high drought and heavy rainfall may cause ground subsidence resulting in shifting slabs.

Building movement may also be caused by other underlying or site-specific issues which require a professional assessment and working knowledge of the local area.

Inner West

Older types of houses tend to have shallower brick or stone footings which are generally more susceptible to shrink-swell action – where the ground noticeably contracts and expands depending on moisture levels – which is associated with moderately reactive clay soils. Old brick and stone foundations need special attention because they may become brittle and are therefore considered less suitable for traditional underpinning methods. Areas affected by these conditions include Balmain, Newtown, Marrickville, Strathfield, Cabarita and Five Dock.

Eastern Suburbs

Many homes in Sydney’s east are built on sand, and particular care needs to be taken with foundation treatment in these soils because they are non-cohesive soils, susceptible to settlement caused by leaking pipes, erosion, wash out and excavation near the property. Vibrations from neighbouring properties which are being developed may also cause ground disturbance and aggravate wall cracking.  Sandy soils sometimes need permeation grouting in addition to resin treatment to strengthen the ground before a home is re-levelled.  Areas commonly affected by these conditions include Bronte, Bondi, Bellevue Hill, Point Piper, Paddington, Surry Hills and Darlinghurst.

Northern Suburbs

This region tends to be prone to movement associated with shrinkage and expansion of moderate to high reactive clay soils. Common triggers are broken pipes leaking water into the ground which will impact older houses with usually shallower footings.  In a drought, tree roots infiltrate clay pipes seeking moisture. Areas affected by these conditions include Ryde, Epping, Eastwood, Denistone and Asquit

Western Sydney

To the west of Sydney, the ground is often formed of highly reactive clay soils which expand and contract aggressively during periods of heavy rain and drought. When paired with older homes, the foundations of brittle and shallow footings offer almost no ability to span over the soft zone on the ground, causing homes to sink.  Brickwork may also feature older style lime mortar which makes walls more susceptible to visible cracking.  As well as sub soil, surface water management is important across larger backyards where rain may collect and run across a property.  Drain repair and drainage solutions may form part of the ground improvement recommendations in areas including Parramatta, Granville, Lakemba, Wentworthville and Cabramatta.

Northern Beaches

Clay and sandy soil are experienced along the full stretch of the Northern Beaches, with coastal facing properties most affected by erosion. Alluvial patches are common in low lying suburbs including Warriewood, Manly Vale and Cromer which are known flood zones.  These suburbs have a high concentration of silty, clay and sand combination soils which may require homes to have slab foundation  On sloping blocks heavily affected by rains, it may also be important to treat the ground underneath driveways and paths to prevent cracking and trip hazards.  Mainmark works along the peninsula including Manly, Seaforth and extending to Palm Beach.

Hills District

While many homes in this area of Sydney have been built more recently, the reactive clay soil may still require resin injection to aid with slab repair and fix cracks in concrete driveways. New housing estates are not immune to sinking, particularly when the ground may not have been prepared properly, resulting in the house settling.   Impacted areas include Castle Hill, Kellyville and Rouse Hill.

Upper North Shore

This area has many larger blocks with single or double-storey homes which may feature old brick and stone foundations. Reactive clay soils can cause these footings to sink over time, and traditional concrete underpinning would be too invasive a process for remediation.  Larger blocks may also be affected by excessive moisture in the ground as trees are removed, which can have a significant impact on foundations. St Ives, Turramurra, Lindfield and Wahroonga are likely impacted.

Lower North Shore

Sandy soils and rocky ground can allow water to flow under homes and cause home foundations to shift. Some properties may also experience run off or leaks from neighbouring pools which weaken the ground and impact foundations.  Many older sandstone and brick homes also feature brick and stone footings which require special attention and are less likely to be suitable for concrete underpinning if the home needs to be relevelled.  Mosman, Cremorne, Neutral Bay, Kirribilli and Crows Nest all form part of this area.

Underpinning Frequently Asked Questions
What is underpinning?

Underpinning is the process of extending the foundation of a building to a deeper layer of soil. This is traditionally done by digging deep holes under the footing and filling the hole with concrete.

What are the alternatives to underpinning a house?

The main alternatives to traditional underpinning are resin injection and screw piles.

Resin injection strengthens the soil beneath the footing by compacting the ground. Screw piles extend the footings to a deeper layer of soil.

What is the cheapest method of underpinning a foundation?

The cost to underpin a footing can vary significantly, and depends on the method adopted, soil condition, accessibility to the failed footing and proximity of other buildings and pavements to the work area.

Traditional underpinning is labour intensive and involves large excavations, so its price does depend on how busy the contractor is. Resin Injection and screw piling have more stable prices.

How much does the underpinning cost?

Traditional underpins vary from $1000 to $4500 per underpin for shallow underpins.

Deeper underpins are more expensive as each excavation requires shoring to make the hole safe.

How much does resin injection underpinning cost?

Resin injection typically costs in the range of $1100 to $1400 per linear meter of the footing to be supported.

How long does it take to underpin a house?

Traditional underpinning required digging holes next to the footing and then filling them with concrete.

The excavation of the holes can take some time and will impact gardens and paths as they will be removed.

Traditional underpinning could take a few days for a single underpin to several weeks.

How long does underpinning last?

Concrete underpins if well-constructed using sound concrete should last more than 50 years.

Is resin injection as good as underpinning?

Resin injection is different to underpinning.

Resin injection involves strengthening the ground beneath the footing, whereas underpinning involves extending the footing to a deeper layer of soil.

What are the dangers of underpinning?

There are several pitfalls when using concrete underpins.

In reactive clay soils, if only part of the footing is underpinned then there will be differential seasonal movement between the underpinned sections of the footing and the rest of the footings.

This difference in seasonal movement will result in large cracks forming in the walls adjacent to the areas that have been underpinned.

Another problem that arises with traditional underpinning is poorly compacted soil adjacent to the underpin acts as a water path to the underside of the underpin and can undermine the underpin.


© 2024 The Mainmark group of companies. ‘Mainmark®’, ‘Terefil®’, ‘Terefirm®’ and ‘Teretek®’ are trademarks of the Mainmark group of companies.

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