Common causes of a shifting house foundation
Homes in many parts of Auckland may experience subsidence that leads to sunken foundations. Visible signs of this occurring at your property may include cracks forming in the exterior walls, a sliding door sticking and windows that become jammed.
Sloping and cracked floors, cracks in block walls, and doors and windows that won’t close properly can all be warning signs of foundation problems. 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 to foundation repair companies for a solution to help ‘underpin’ their home.
Auckland is often affected by challenging weather conditions. Many properties are built on soils that react to changes in moisture levels, with some clay foundation soils known to expand and contract following periods of heavy rain or drought. With its coastal aspect, the city’s extreme weather events can include torrential rain and localised storm activity at different times of year. However, properties in Auckland and surrounding suburbs may face a wide range of factors that can lead to structural 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’.
- Torrential rain: Auckland receives a significant amount of rain, with rain falls in August 2019 breaking the record for the greatest number of consecutive wet days. After heavy rainfall often comes flooding and sodden backyards that don’t have a chance to dry out due to ongoing cold and wet weather conditions. If clay soils become oversaturated, the ground loses its strength and footings settle through the clay. This is when house re-piling or house re-levelling is required.
- 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 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 which result in water spilling into the ground, impacting soil and the stability of house foundations.
- Older constructions: with many homes in the Auckland area dating back to the mid-1900s or earlier, it’s important to note that construction methods accepted at the time may contribute to foundation stability being compromised today. In some cases, a ring beam foundation will be smaller than is required by the current building code, which means changes in soil conditions over time, or the added weight of additions and renovations, may lead to structural movement.
The Mainmark solution
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 Auckland’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 to raise sinking foundations 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 Auckland. The process is extremely quick; most house re-levelling, concrete block wall repair 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 of foundation repair using traditional methods can be high due to the invasive nature of concrete underpinning or re-piling, 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:
- your location – with different properties having different site restrictions and access considerations
- the actual cause of the problem – factoring in what other things need to be resolved as part of the remediation works eg. leaking pipes and drainage
- the nature and condition of the foundation soil – including an assessment of the soil type and any local issues that may contribute to the ground’s stability
- the type and profile of the building footings – are the existing footings damaged or in need of replacement or reinforcement?
- the surroundings eg. adjacent buildings, retaining walls, trees or bushland
- 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 – this may vary depending on the extent of the remediation work required, and the footprint of the building.
Why choose Mainmark?
When it comes to underpinning the foundations of your house, it’s important to call in experienced ground engineering consultants for an appraisal which can help to quickly diagnose the issue and find a comprehensive solution tailored to your home, including an estimate of the foundation repair cost. 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 foundation repair process. In contrast, traditional concrete foundation repair and re-piling involve extensive works under the home, with families needing to vacate the property for a longer period while the foundation contractors conduct the remediation and fix damaged sections of the home.
The Mainmark solution is:
Cost effective – compared to traditional underpinning, plus no hidden fees
Non-invasive – our application process is like keyhole surgery, with no major excavation or impact on the home’s structure
Resident friendly – work is carried out with minimal disruption; in most cases you won’t need to move out
Time efficient – on average we can get your home back to level in little as a day, or within 1 – 2 weeks depending on the technologies we utilise
Worry-free – our resin product comes backed by a 50-year warranty for added peace of mind
Accurate – using state-of-the-art technology and careful monitoring throughout the process, Mainmark’s qualified technicians can often get the level accuracy to within millimetres
Reputable – our specialised methods have been mastered for more than 20 years with thousands of satisfied customers.
Auckland by location
Auckland is primarily built on 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 buildings and other structures to be more aggressively affected by subsidence, meaning their foundations ‘sink’ into the ground.
Set over a hilly landscape, Auckland’s suburbs may also be impacted by natural watercourses that cause soils to shift if they are poorly compacted or mixed with other kinds of fill material. However, building movement may also be caused by other underlying or site-specific issues which require professional assessment and a working knowledge of the local area.
Residential foundation styles in Auckland have also evolved over time and each type of housing construction can display different signs of foundation damage. Understanding these structural differences helps to identify the symptoms of subsidence – such as wall cracks, a stuck window or jammed sliding door – and informs the best approach for foundation repairs.
- Central Auckland: In the mid-1930s, a ring beam – or continuous reinforced concrete perimeter foundation wall – was introduced to building construction to combat termite attack and accommodate movement caused by the reactive clay soils of Auckland. These foundations for typically timber-framed buildings are common beneath many older properties in this part of the city. However, these original foundations tend to be smaller than those found under more contemporary homes, making them more susceptible to seasonal movement. Renovations to the house over time, and neighbouring construction or excavation for a pool, may further contribute to ground movement and the need for house lifters in areas including Remuera, Newmarket, Parnell, Mount Albert, Mount Roskill
- North Shore: incorporating a number of coastal suburbs, and a range of older homes and higher density housing, this popular district has many pockets of reactive clay soils which noticeably contract and expand depending on moisture levels. The growth of infilling development in these urban areas, where single-storey homes are converted to two-storey dwellings or townhouses, can further contribute to cracks forming in the perimeter walls of established homes, either due to nearby construction or increased weight of building additions. Areas affected, where homeowners may be seeking house foundation specialist services, include Takapanu, Glenfield, Albany and Orewa Triangle.
- West Auckland: featuring some of Auckland’s leafiest suburbs, many homes in this area are positioned on larger, steeper blocks which neighbour parks, bushland and the shorefront. Surface water management is important across larger backyards where rain may collect and run across a property, impacting soils and ground stability. During drought periods, tree roots may also infiltrate underground pipes seeking moisture, causing water leaks into the foundation ground and impacting shallower footings. Drain repair and drainage solutions may form part of the ground improvement recommendations in suburbs including Henderson, New Lynn, Kelston, Sunnyvale, Te Atatu South/Peninsula, Massey, Westharbour, Hobsonville and Titirangi.
- South Auckland and eastern suburbs: this part of the city features many modern homes often built on a conventional concrete slab foundation, or what are known as raft or waffle slab foundations which were introduced in the 90s. Mainmark is a foundation specialist that can help to devise the best method of home foundation repair to suit each home, targeting unstable ground that may be contributing to subsidence. In newer areas, vibrations from development in neighbouring properties may also cause ground disturbance and aggravate cracking, often visible on internal walls and the brick veneer exterior. Areas affected by these conditions may include East Tamaki, Highland Park, Howick, Cockle Bay, Botany Downs, Dannemora and Pakuranga.