Homes in many parts of Sydney may experience ground instability that leads to sunken foundations. Sinking and cracked floors, a crack in the wall or concrete slab, 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, it can result in significant and expensive damage, particularly if left unaddressed. This is when homeowners may look for solutions that can effectively ‘underpin’ their home, a process sometimes referred to as house restumping or reblocking.
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:
Mainmark offers some of the most advanced non-invasive resin injection and grout technologies to quickly correct foundation ground issues with minimal mess or disruption, perfected over more than 20 years in business. With a sound knowledge of Sydney’s unique local conditions, Mainmark utilises its Teretek® engineered resin injection 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 raises sinking floors and reduces wall cracking, all at a fraction of the cost of traditional underpinning, and with no detrimental effects on the environment.
Mainmark has successfully raised and re-levelled hundreds of homes and driveways throughout the Sydney region. The process is extremely quick; most house re-levelling and concrete slab lifting takes less than a day, and driveways and slabs can be driven on within hours once the application is complete.
As part of Mainmark’s expanded capabilities, we also provide ground improvements solutions specific to coastal areas.
The cost to underpin a house using traditional methods can be high due to the invasive nature of concrete underpinning, which is generally a lengthy and messy process. Teretek is the modern way to re-support the footings in your house. It’s applied like keyhole surgery and most jobs can be done in a day, usually reducing the cost of the works when compared to traditional underpinning. As every home is different, Mainmark finds the best solution to treat the root of the problem. The cost of each job will vary according to:
Calling in experienced ground engineering consultants for an appraisal can help to quickly diagnose the issue and find a solution tailored to your home. By using Teretek to address building foundation problems, there is 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 underpinning involves excavation to make large holes under the home’s footings, pouring in concrete, waiting for it to set and then jacking the house up off the concrete blocks. The Mainmark solution is:
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.
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.
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.
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 Asquith.
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.
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.
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.
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.
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.